Example #1
0
def DDrppi_mocks(autocorr,
                 cosmology,
                 nthreads,
                 pimax,
                 binfile,
                 RA1,
                 DEC1,
                 CZ1,
                 weights1=None,
                 RA2=None,
                 DEC2=None,
                 CZ2=None,
                 weights2=None,
                 is_comoving_dist=False,
                 verbose=False,
                 output_rpavg=False,
                 fast_divide=False,
                 xbin_refine_factor=2,
                 ybin_refine_factor=2,
                 zbin_refine_factor=1,
                 max_cells_per_dim=100,
                 c_api_timer=False,
                 isa=r'fastest',
                 weight_type=None):
    """
    Calculate the 2-D pair-counts corresponding to the projected correlation
    function, :math:`\\xi(r_p, \pi)`. Pairs which are separated by less
    than the ``rp`` bins (specified in ``binfile``) in the
    X-Y plane, and less than ``pimax`` in the Z-dimension are
    counted. The input positions are expected to be on-sky co-ordinates.
    This module is suitable for calculating correlation functions for mock
    catalogs.
    
    If ``weights`` are provided, the resulting pair counts are weighted.  The
    weighting scheme depends on ``weight_type``.

    Returns a numpy structured array containing the pair counts for the
    specified bins.


    .. note:: that this module only returns pair counts and not the actual
       correlation function :math:`\\xi(r_p, \pi)` or :math:`wp(r_p)`. See the
       utilities :py:mod:`Corrfunc.utils.convert_3d_counts_to_cf` and
       :py:mod:`Corrfunc.utils.convert_rp_pi_counts_to_wp` for computing 
       :math:`\\xi(r_p, \pi)` and :math:`wp(r_p)` respectively from the 
       pair counts.


    Parameters
    -----------

    autocorr : boolean, required
        Boolean flag for auto/cross-correlation. If autocorr is set to 1,
        then the second set of particle positions are not required.

    cosmology : integer, required
        Integer choice for setting cosmology. Valid values are 1->LasDamas
        cosmology and 2->Planck cosmology. If you need arbitrary cosmology,
        easiest way is to convert the ``CZ`` values into co-moving distance,
        based on your preferred cosmology. Set ``is_comoving_dist=True``, to
        indicate that the co-moving distance conversion has already been done.

        Choices:
                 1. LasDamas cosmology. :math:`\\Omega_m=0.25`, :math:`\\Omega_\Lambda=0.75`
                 2. Planck   cosmology. :math:`\\Omega_m=0.302`, :math:`\\Omega_\Lambda=0.698`

        To setup a new cosmology, add an entry to the function,
        ``init_cosmology`` in ``ROOT/utils/cosmology_params.c`` and re-install
        the entire package.

    nthreads : integer
        The number of OpenMP threads to use. Has no effect if OpenMP was not
        enabled during library compilation.

    pimax : double
        A double-precision value for the maximum separation along
        the Z-dimension. 

        Distances along the :math:`\\pi` direction are binned with unit
        depth. For instance, if ``pimax=40``, then 40 bins will be created
        along the ``pi`` direction. Only pairs with ``0 <= dz < pimax``
        are counted (no equality).

    binfile: string or an list/array of floats
        For string input: filename specifying the ``rp`` bins for
        ``DDrppi_mocks``. The file should contain white-space separated values
        of (rpmin, rpmax)  for each ``rp`` wanted. The bins need to be
        contiguous and sorted in increasing order (smallest bins come first).

        For array-like input: A sequence of ``rp`` values that provides the
        bin-edges. For example,
        ``np.logspace(np.log10(0.1), np.log10(10.0), 15)`` is a valid
        input specifying **14** (logarithmic) bins between 0.1 and 10.0. This
        array does not need to be sorted.         

    RA1 : array-like, real (float/double)
        The array of Right Ascensions for the first set of points. RA's
        are expected to be in [0.0, 360.0], but the code will try to fix cases
        where the RA's are in [-180, 180.0]. For peace of mind, always supply
        RA's in [0.0, 360.0].

        Calculations are done in the precision of the supplied arrays.

    DEC1 : array-like, real (float/double)
        Array of Declinations for the first set of points. DEC's are expected
        to be in the [-90.0, 90.0], but the code will try to fix cases where
        the DEC's are in [0.0, 180.0]. Again, for peace of mind, always supply
        DEC's in [-90.0, 90.0].

        Must be of same precision type as RA1.

    CZ1 : array-like, real (float/double)
        Array of (Speed Of Light * Redshift) values for the first set of
        points. Code will try to detect cases where ``redshifts`` have been
        passed and multiply the entire array with the ``speed of light``.
 
        If is_comoving_dist is set, then ``CZ1`` is interpreted as the
        co-moving distance, rather than `cz`.
       
    weights1 : array_like, real (float/double), optional
        A scalar, or an array of weights of shape (n_weights, n_positions) or (n_positions,).
        `weight_type` specifies how these weights are used; results are returned
        in the `weightavg` field.  If only one of weights1 and weights2 is
        specified, the other will be set to uniform weights.

    RA2 : array-like, real (float/double)
        The array of Right Ascensions for the second set of points. RA's
        are expected to be in [0.0, 360.0], but the code will try to fix cases
        where the RA's are in [-180, 180.0]. For peace of mind, always supply
        RA's in [0.0, 360.0].

        Must be of same precision type as RA1/DEC1/CZ1.

    DEC2 : array-like, real (float/double)
        Array of Declinations for the second set of points. DEC's are expected
        to be in the [-90.0, 90.0], but the code will try to fix cases where
        the DEC's are in [0.0, 180.0]. Again, for peace of mind, always supply
        DEC's in [-90.0, 90.0].

        Must be of same precision type as RA1/DEC1/CZ1.

    CZ2 : array-like, real (float/double)
        Array of (Speed Of Light * Redshift) values for the second set of
        points. Code will try to detect cases where ``redshifts`` have been
        passed and multiply the entire array with the ``speed of light``.

        If is_comoving_dist is set, then ``CZ2`` is interpreted as the
        co-moving distance, rather than `cz`.

        Must be of same precision type as RA1/DEC1/CZ1.
        
    weights2 : array-like, real (float/double), optional
        Same as weights1, but for the second set of positions

    is_comoving_dist : boolean (default false)
        Boolean flag to indicate that ``cz`` values have already been
        converted into co-moving distances. This flag allows arbitrary
        cosmologies to be used in ``Corrfunc``.

    verbose : boolean (default false)
        Boolean flag to control output of informational messages

    output_rpavg : boolean (default false)
        Boolean flag to output the average ``rp`` for each bin. Code will
        run slower if you set this flag.
    
        If you are calculating in single-precision, ``rpavg`` will suffer
        suffer from numerical loss of precision and can not be trusted. If 
        you need accurate ``rpavg`` values, then pass in double precision 
        arrays for the particle positions.
    
    fast_divide : boolean (default false)
        Boolean flag to replace the division in ``AVX`` implementation with an
        approximate reciprocal, followed by two Newton-Raphson steps. Improves
        runtime by ~15-20%. Loss of precision is at the 5-6th decimal place.

    (xyz)bin_refine_factor : integer, default is (2,2,1); typically within [1-3]
        Controls the refinement on the cell sizes. Can have up to a 20% impact
        on runtime.

    max_cells_per_dim: integer, default is 100, typical values in [50-300]
        Controls the maximum number of cells per dimension. Total number of
        cells can be up to (max_cells_per_dim)^3. Only increase if ``rpmax`` is
        too small relative to the boxsize (and increasing helps the runtime).

    c_api_timer : boolean (default false)
        Boolean flag to measure actual time spent in the C libraries. Here
        to allow for benchmarking and scaling studies.

    isa : string (default ``fastest``)
        Controls the runtime dispatch for the instruction set to use. Possible
        options are: [``fastest``, ``avx``, ``sse42``, ``fallback``]

        Setting isa to ``fastest`` will pick the fastest available instruction
        set on the current computer. However, if you set ``isa`` to, say,
        ``avx`` and ``avx`` is not available on the computer, then the code
        will revert to using ``fallback`` (even though ``sse42`` might be
        available).

        Unless you are benchmarking the different instruction sets, you should
        always leave ``isa`` to the default value. And if you *are*
        benchmarking, then the string supplied here gets translated into an
        ``enum`` for the instruction set defined in ``utils/defs.h``.
        
    weight_type : string, optional
        The type of weighting to apply.  One of ["pair_product", None].  Default: None.

    Returns
    --------

    results : Numpy structured array

        A numpy structured array containing [rpmin, rpmax, rpavg, pimax, npairs, weightavg]
        for each radial bin specified in the ``binfile``. If ``output_ravg`` is
        not set, then ``rpavg`` will be set to 0.0 for all bins; similarly for
        ``weightavg``. ``npairs``
        contains the number of pairs in that bin and can be used to compute the
        actual :math:`\\xi(r_p, \pi)` or :math:`wp(rp)` by combining with
        (DR, RR) counts.

    api_time : float, optional
        Only returned if ``c_api_timer`` is set.  ``api_time`` measures only the time
        spent within the C library and ignores all python overhead.

    Example
    --------

    >>> from __future__ import print_function
    >>> import numpy as np
    >>> from os.path import dirname, abspath, join as pjoin
    >>> import Corrfunc
    >>> from Corrfunc.mocks.DDrppi_mocks import DDrppi_mocks
    >>> import math
    >>> binfile = pjoin(dirname(abspath(Corrfunc.__file__)),
    ...                 "../mocks/tests/", "bins")
    >>> N = 100000
    >>> boxsize = 420.0
    >>> seed = 42
    >>> np.random.seed(seed)
    >>> X = np.random.uniform(-0.5*boxsize, 0.5*boxsize, N)
    >>> Y = np.random.uniform(-0.5*boxsize, 0.5*boxsize, N)
    >>> Z = np.random.uniform(-0.5*boxsize, 0.5*boxsize, N)
    >>> weights = np.ones_like(X)
    >>> CZ = np.sqrt(X*X + Y*Y + Z*Z)
    >>> inv_cz = 1.0/CZ
    >>> X *= inv_cz
    >>> Y *= inv_cz
    >>> Z *= inv_cz
    >>> DEC = 90.0 - np.arccos(Z)*180.0/math.pi
    >>> RA = (np.arctan2(Y, X)*180.0/math.pi) + 180.0
    >>> autocorr = 1
    >>> cosmology = 1
    >>> nthreads = 2
    >>> pimax = 40.0
    >>> results = DDrppi_mocks(autocorr, cosmology, nthreads,
    ...                        pimax, binfile, RA, DEC, CZ,
    ...                        weights1=weights, weight_type='pair_product',
    ...                        output_rpavg=True, is_comoving_dist=True)
    >>> for r in results[519:]: print("{0:10.6f} {1:10.6f} {2:10.6f} {3:10.1f}"
    ...                               " {4:10d} {5:10.6f}".format(r['rmin'], r['rmax'],
    ...                               r['rpavg'], r['pimax'], r['npairs'], r['weightavg']))
    ...                         # doctest: +NORMALIZE_WHITESPACE
     11.359969  16.852277  14.285169       40.0     104850   1.000000
     16.852277  25.000000  21.181246        1.0     274144   1.000000
     16.852277  25.000000  21.190844        2.0     272876   1.000000
     16.852277  25.000000  21.183321        3.0     272294   1.000000
     16.852277  25.000000  21.188486        4.0     272506   1.000000
     16.852277  25.000000  21.170832        5.0     272100   1.000000
     16.852277  25.000000  21.165379        6.0     271788   1.000000
     16.852277  25.000000  21.175246        7.0     270040   1.000000
     16.852277  25.000000  21.187417        8.0     269492   1.000000
     16.852277  25.000000  21.172066        9.0     269682   1.000000
     16.852277  25.000000  21.182460       10.0     268266   1.000000
     16.852277  25.000000  21.170594       11.0     268744   1.000000
     16.852277  25.000000  21.178608       12.0     266820   1.000000
     16.852277  25.000000  21.187184       13.0     266510   1.000000
     16.852277  25.000000  21.184937       14.0     265484   1.000000
     16.852277  25.000000  21.180184       15.0     265258   1.000000
     16.852277  25.000000  21.191504       16.0     262952   1.000000
     16.852277  25.000000  21.187746       17.0     262602   1.000000
     16.852277  25.000000  21.189778       18.0     260206   1.000000
     16.852277  25.000000  21.188882       19.0     259410   1.000000
     16.852277  25.000000  21.185684       20.0     256806   1.000000
     16.852277  25.000000  21.194036       21.0     255574   1.000000
     16.852277  25.000000  21.184115       22.0     255406   1.000000
     16.852277  25.000000  21.178255       23.0     252394   1.000000
     16.852277  25.000000  21.184644       24.0     252220   1.000000
     16.852277  25.000000  21.187020       25.0     251668   1.000000
     16.852277  25.000000  21.183827       26.0     249648   1.000000
     16.852277  25.000000  21.183121       27.0     247160   1.000000
     16.852277  25.000000  21.180872       28.0     246238   1.000000
     16.852277  25.000000  21.185251       29.0     246030   1.000000
     16.852277  25.000000  21.183488       30.0     242124   1.000000
     16.852277  25.000000  21.194538       31.0     242426   1.000000
     16.852277  25.000000  21.190702       32.0     239778   1.000000
     16.852277  25.000000  21.188985       33.0     239046   1.000000
     16.852277  25.000000  21.187092       34.0     237640   1.000000
     16.852277  25.000000  21.185515       35.0     236256   1.000000
     16.852277  25.000000  21.190278       36.0     233536   1.000000
     16.852277  25.000000  21.183240       37.0     233274   1.000000
     16.852277  25.000000  21.183796       38.0     231628   1.000000
     16.852277  25.000000  21.200668       39.0     230378   1.000000
     16.852277  25.000000  21.181153       40.0     229006   1.000000

    """
    try:
        from Corrfunc._countpairs_mocks import countpairs_rp_pi_mocks as\
            DDrppi_extn
    except ImportError:
        msg = "Could not import the C extension for the on-sky"\
              "pair counter."
        raise ImportError(msg)

    import numpy as np
    from warnings import warn
    from Corrfunc.utils import translate_isa_string_to_enum, fix_ra_dec,\
        return_file_with_rbins, convert_to_native_endian,\
        is_native_endian
    from future.utils import bytes_to_native_str

    # Broadcast scalar weights to arrays
    if weights1 is not None:
        weights1 = np.atleast_1d(weights1)
    if weights2 is not None:
        weights2 = np.atleast_1d(weights2)

    if not autocorr:
        if RA2 is None or DEC2 is None or CZ2 is None:
            msg = "Must pass valid arrays for RA2/DEC2/CZ2 for "\
                  "computing cross-correlation"
            raise ValueError(msg)

        # If only one set of points has weights, set the other to uniform weights
        if weights1 is None and weights2 is not None:
            weights1 = np.ones_like(weights2)
        if weights2 is None and weights1 is not None:
            weights2 = np.ones_like(weights1)

    else:
        RA2 = np.empty(1)
        DEC2 = np.empty(1)
        CZ2 = np.empty(1)

    # Warn about non-native endian arrays
    if not all(
            is_native_endian(arr)
            for arr in [RA1, DEC1, CZ1, weights1, RA2, DEC2, CZ2, weights2]):
        warn(
            'One or more input array has non-native endianness!  A copy will be made with the correct endianness.'
        )
    RA1, DEC1, CZ1, weights1, RA2, DEC2, CZ2, weights2 = [
        convert_to_native_endian(arr)
        for arr in [RA1, DEC1, CZ1, weights1, RA2, DEC2, CZ2, weights2]
    ]

    fix_ra_dec(RA1, DEC1)
    if autocorr == 0:
        fix_ra_dec(RA2, DEC2)

    # Passing None parameters breaks the parsing code, so avoid this
    kwargs = {}
    for k in ['weights1', 'weights2', 'weight_type', 'RA2', 'DEC2', 'CZ2']:
        v = locals()[k]
        if v is not None:
            kwargs[k] = v

    integer_isa = translate_isa_string_to_enum(isa)
    rbinfile, delete_after_use = return_file_with_rbins(binfile)
    extn_results, api_time = DDrppi_extn(autocorr,
                                         cosmology,
                                         nthreads,
                                         pimax,
                                         rbinfile,
                                         RA1,
                                         DEC1,
                                         CZ1,
                                         is_comoving_dist=is_comoving_dist,
                                         verbose=verbose,
                                         output_rpavg=output_rpavg,
                                         fast_divide=fast_divide,
                                         xbin_refine_factor=xbin_refine_factor,
                                         ybin_refine_factor=ybin_refine_factor,
                                         zbin_refine_factor=zbin_refine_factor,
                                         max_cells_per_dim=max_cells_per_dim,
                                         c_api_timer=c_api_timer,
                                         isa=integer_isa,
                                         **kwargs)
    if extn_results is None:
        msg = "RuntimeError occurred"
        raise RuntimeError(msg)

    if delete_after_use:
        import os
        os.remove(rbinfile)

    results_dtype = np.dtype([(bytes_to_native_str(b'rmin'), np.float),
                              (bytes_to_native_str(b'rmax'), np.float),
                              (bytes_to_native_str(b'rpavg'), np.float),
                              (bytes_to_native_str(b'pimax'), np.float),
                              (bytes_to_native_str(b'npairs'), np.uint64),
                              (bytes_to_native_str(b'weightavg'), np.float)])
    results = np.array(extn_results, dtype=results_dtype)

    if not c_api_timer:
        return results
    else:
        return results, api_time
Example #2
0
def DDtheta_mocks(autocorr, nthreads, binfile,
                  RA1, DEC1, weights1=None,
                  RA2=None, DEC2=None, weights2=None,
                  link_in_dec=True, link_in_ra=True,
                  verbose=False, output_thetaavg=False,
                  fast_acos=False, ra_refine_factor=2,
                  dec_refine_factor=2, max_cells_per_dim=100,
                  copy_particles=True, enable_min_sep_opt=True,
                  c_api_timer=False, isa=r'fastest', weight_type=None):
    """
    Function to compute the angular correlation function for points on
    the sky (i.e., mock catalogs or observed galaxies).

    Returns a numpy structured array containing the pair counts for the
    specified angular bins.

    If ``weights`` are provided, the resulting pair counts are weighted.  The
    weighting scheme depends on ``weight_type``.


    .. note:: This module only returns pair counts and not the actual
       correlation function :math:`\\omega(\theta)`. See
       :py:mod:`Corrfunc.utils.convert_3d_counts_to_cf` for computing
       :math:`\\omega(\theta)` from the pair counts returned.


    Parameters
    -----------

    autocorr : boolean, required
        Boolean flag for auto/cross-correlation. If autocorr is set to 1,
        then the second set of particle positions are not required.

    nthreads : integer
        Number of threads to use.

    binfile: string or an list/array of floats. Units: degrees.
        For string input: filename specifying the ``theta`` bins for
        ``DDtheta_mocks``. The file should contain white-space separated values
        of (thetamin, thetamax)  for each ``theta`` wanted. The bins need to be
        contiguous and sorted in increasing order (smallest bins come first).

        For array-like input: A sequence of ``theta`` values that provides the
        bin-edges. For example,
        ``np.logspace(np.log10(0.1), np.log10(10.0), 15)`` is a valid
        input specifying **14** (logarithmic) bins between 0.1 and 10.0
        degrees. This array does not need to be sorted.

    RA1 : array-like, real (float/double)
        The array of Right Ascensions for the first set of points. RA's
        are expected to be in [0.0, 360.0], but the code will try to fix cases
        where the RA's are in [-180, 180.0]. For peace of mind, always supply
        RA's in [0.0, 360.0].

        Calculations are done in the precision of the supplied arrays.

    DEC1 : array-like, real (float/double)
        Array of Declinations for the first set of points. DEC's are expected
        to be in the [-90.0, 90.0], but the code will try to fix cases where
        the DEC's are in [0.0, 180.0]. Again, for peace of mind, always supply
        DEC's in [-90.0, 90.0].
        Must be of same precision type as RA1.

    weights1 : array_like, real (float/double), optional
        A scalar, or an array of weights of shape (n_weights, n_positions) or
        (n_positions,). `weight_type` specifies how these weights are used;
        results are returned in the `weightavg` field.  If only one of weights1
        and weights2 is specified, the other will be set to uniform weights.

    RA2 : array-like, real (float/double)
        The array of Right Ascensions for the second set of points. RA's
        are expected to be in [0.0, 360.0], but the code will try to fix cases
        where the RA's are in [-180, 180.0]. For peace of mind, always supply
        RA's in [0.0, 360.0].
        Must be of same precision type as RA1/DEC1.

    DEC2 : array-like, real (float/double)
        Array of Declinations for the second set of points. DEC's are expected
        to be in the [-90.0, 90.0], but the code will try to fix cases where
        the DEC's are in [0.0, 180.0]. Again, for peace of mind, always supply
        DEC's in [-90.0, 90.0].
        Must be of same precision type as RA1/DEC1.

    weights2 : array-like, real (float/double), optional
        Same as weights1, but for the second set of positions

    link_in_dec : boolean (default True)
        Boolean flag to create lattice in Declination. Code runs faster with
        this option. However, if the angular separations are too small, then
        linking in declination might produce incorrect results. When running
        for the first time, check your results by comparing with the output
        of the code for ``link_in_dec=False`` and ``link_in_ra=False``.

    link_in_ra : boolean (default True)
        Boolean flag to create lattice in Right Ascension. Setting this option
        implies ``link_in_dec=True``. Similar considerations as ``link_in_dec``
        described above.

        If you disable both ``link_in_dec`` and ``link_in_ra``, then
        the code reduces to a brute-force pair counter. No lattices are created
        at all. For very small angular separations, the brute-force method
        might be the most numerically stable method.

    verbose : boolean (default false)
        Boolean flag to control output of informational messages

    output_thetaavg : boolean (default false)
        Boolean flag to output the average ``\theta`` for each bin. Code will
        run slower if you set this flag.

        If you are calculating in single-precision, ``thetaavg`` will
        suffer from numerical loss of precision and can not be trusted. If you
        need accurate ``thetaavg`` values, then pass in double precision arrays
        for ``RA/DEC``.

        Code will run significantly slower if you enable this option.
        Use the keyword ``fast_acos`` if you can tolerate some loss of
        precision.

    fast_acos : boolean (default false)
        Flag to use numerical approximation for the ``arccos`` - gives better
        performance at the expense of some precision. Relevant only if
        ``output_thetaavg==True``.

        Developers: Two versions already coded up in ``utils/fast_acos.h``,
        so you can choose the version you want. There are also notes on how
        to implement faster (and less accurate) functions, particularly
        relevant if you know your ``theta`` range is limited. If you implement
        a new version, then you will have to reinstall the entire Corrfunc
        package.

        Note: Tests will fail if you run the tests with``fast_acos=True``.

    (radec)_refine_factor : integer, default is (2,2); typically within [1-5]
        Controls the refinement on the cell sizes. Can have up to a 20% impact
        on runtime.

        Only two refine factors are to be specified and these
        correspond to ``ra`` and ``dec`` (rather, than the usual three of
        ``(xyz)bin_refine_factor`` for all other correlation functions).

    max_cells_per_dim : integer, default is 100, typical values in [50-300]
        Controls the maximum number of cells per dimension. Total number of
        cells can be up to (max_cells_per_dim)^3. Only increase if ``thetamax``
        is too small relative to the boxsize (and increasing helps the
        runtime).

    copy_particles: boolean (default True)
        Boolean flag to make a copy of the particle positions
        If set to False, the particles will be re-ordered in-place

        .. versionadded:: 2.3.0

    enable_min_sep_opt: boolean (default true)
        Boolean flag to allow optimizations based on min. separation between
        pairs of cells. Here to allow for comparison studies.

        .. versionadded:: 2.3.0

    c_api_timer : boolean (default false)
        Boolean flag to measure actual time spent in the C libraries. Here
        to allow for benchmarking and scaling studies.

    isa: string, case-insensitive (default ``fastest``)
        Controls the runtime dispatch for the instruction set to use. Options
        are: [``fastest``, ``avx512f``, ``avx``, ``sse42``, ``fallback``]

        Setting isa to ``fastest`` will pick the fastest available instruction
        set on the current computer. However, if you set ``isa`` to, say,
        ``avx`` and ``avx`` is not available on the computer, then the code
        will revert to using ``fallback`` (even though ``sse42`` might be
        available).

        Unless you are benchmarking the different instruction sets, you should
        always leave ``isa`` to the default value. And if you *are*
        benchmarking, then the string supplied here gets translated into an
        ``enum`` for the instruction set defined in ``utils/defs.h``.

    weight_type : string, optional (default None)
        The type of weighting to apply.  One of ["pair_product", None].

    Returns
    --------

    results : Numpy structured array
        A numpy structured array containing [thetamin, thetamax, thetaavg,
        npairs, weightavg] for each angular bin specified in the ``binfile``.
        If ``output_thetaavg`` is not set then ``thetavg`` will be set to 0.0
        for all bins; similarly for ``weightavg``. ``npairs`` contains the
        number of pairs in that bin.

    api_time : float, optional
        Only returned if ``c_api_timer`` is set.  ``api_time`` measures only
        the time spent within the C library and ignores all python overhead.

    Example
    --------

    >>> from __future__ import print_function
    >>> import numpy as np
    >>> import time
    >>> from math import pi
    >>> from os.path import dirname, abspath, join as pjoin
    >>> import Corrfunc
    >>> from Corrfunc.mocks.DDtheta_mocks import DDtheta_mocks
    >>> binfile = pjoin(dirname(abspath(Corrfunc.__file__)),
    ...                 "../mocks/tests/", "angular_bins")
    >>> N = 100000
    >>> nthreads = 4
    >>> seed = 42
    >>> np.random.seed(seed)
    >>> RA = np.random.uniform(0.0, 2.0*pi, N)*180.0/pi
    >>> cos_theta = np.random.uniform(-1.0, 1.0, N)
    >>> DEC = 90.0 - np.arccos(cos_theta)*180.0/pi
    >>> weights = np.ones_like(RA)
    >>> autocorr = 1
    >>> for isa in ['AVX', 'SSE42', 'FALLBACK']:
    ...     for link_in_dec in [False, True]:
    ...         for link_in_ra in [False, True]:
    ...             results = DDtheta_mocks(autocorr, nthreads, binfile,
    ...                         RA, DEC, output_thetaavg=True,
    ...                         weights1=weights, weight_type='pair_product',
    ...                         link_in_dec=link_in_dec, link_in_ra=link_in_ra,
    ...                         isa=isa, verbose=True)
    >>> for r in results: print("{0:10.6f} {1:10.6f} {2:10.6f} {3:10d} {4:10.6f}".
    ...                         format(r['thetamin'], r['thetamax'],
    ...                         r['thetaavg'], r['npairs'], r['weightavg']))
    ...                         # doctest: +NORMALIZE_WHITESPACE
      0.010000   0.014125   0.012272         62   1.000000
      0.014125   0.019953   0.016978        172   1.000000
      0.019953   0.028184   0.024380        298   1.000000
      0.028184   0.039811   0.034321        598   1.000000
      0.039811   0.056234   0.048535       1164   1.000000
      0.056234   0.079433   0.068385       2438   1.000000
      0.079433   0.112202   0.096631       4658   1.000000
      0.112202   0.158489   0.136834       9414   1.000000
      0.158489   0.223872   0.192967      19098   1.000000
      0.223872   0.316228   0.272673      37848   1.000000
      0.316228   0.446684   0.385344      75520   1.000000
      0.446684   0.630957   0.543973     150938   1.000000
      0.630957   0.891251   0.768406     301854   1.000000
      0.891251   1.258925   1.085273     599896   1.000000
      1.258925   1.778279   1.533461    1200238   1.000000
      1.778279   2.511886   2.166009    2396338   1.000000
      2.511886   3.548134   3.059159    4775162   1.000000
      3.548134   5.011872   4.321445    9532582   1.000000
      5.011872   7.079458   6.104214   19001930   1.000000
      7.079458  10.000000   8.622400   37842502   1.000000

    """

    try:
        from Corrfunc._countpairs_mocks import countpairs_theta_mocks as\
            DDtheta_mocks_extn
    except ImportError:
        msg = "Could not import the C extension for the angular "\
              "correlation function for mocks."
        raise ImportError(msg)

    import numpy as np
    from Corrfunc.utils import translate_isa_string_to_enum, fix_ra_dec,\
        return_file_with_rbins, convert_to_native_endian,\
        sys_pipes, process_weights
    from future.utils import bytes_to_native_str

    if autocorr == 0:
        if RA2 is None or DEC2 is None:
            msg = "Must pass valid arrays for RA2/DEC2 for "\
                  "computing cross-correlation"
            raise ValueError(msg)
    else:
        RA2 = np.empty(1)
        DEC2 = np.empty(1)

    weights1, weights2 = process_weights(weights1, weights2, RA1, RA2, weight_type, autocorr)

    # Ensure all input arrays are native endian
    RA1, DEC1, weights1, RA2, DEC2, weights2 = [
            convert_to_native_endian(arr, warn=True) for arr in
            [RA1, DEC1, weights1, RA2, DEC2, weights2]]

    fix_ra_dec(RA1, DEC1)
    if autocorr == 0:
        fix_ra_dec(RA2, DEC2)

    if link_in_ra is True:
        link_in_dec = True


    # Passing None parameters breaks the parsing code, so avoid this
    kwargs = {}
    for k in ['weights1', 'weights2', 'weight_type', 'RA2', 'DEC2']:
        v = locals()[k]
        if v is not None:
            kwargs[k] = v

    integer_isa = translate_isa_string_to_enum(isa)
    rbinfile, delete_after_use = return_file_with_rbins(binfile)
    with sys_pipes():
      extn_results = DDtheta_mocks_extn(autocorr, nthreads, rbinfile,
                                        RA1, DEC1,
                                        verbose=verbose,
                                        link_in_dec=link_in_dec,
                                        link_in_ra=link_in_ra,
                                        output_thetaavg=output_thetaavg,
                                        fast_acos=fast_acos,
                                        ra_refine_factor=ra_refine_factor,
                                        dec_refine_factor=dec_refine_factor,
                                        max_cells_per_dim=max_cells_per_dim,
                                        copy_particles=copy_particles,
                                        enable_min_sep_opt=enable_min_sep_opt,
                                        c_api_timer=c_api_timer,
                                        isa=integer_isa, **kwargs)
    if extn_results is None:
        msg = "RuntimeError occurred"
        raise RuntimeError(msg)
    else:
        extn_results, api_time = extn_results

    if delete_after_use:
        import os
        os.remove(rbinfile)

    results_dtype = np.dtype([(bytes_to_native_str(b'thetamin'), np.float),
                              (bytes_to_native_str(b'thetamax'), np.float),
                              (bytes_to_native_str(b'thetaavg'), np.float),
                              (bytes_to_native_str(b'npairs'), np.uint64),
                              (bytes_to_native_str(b'weightavg'), np.float)])
    results = np.array(extn_results, dtype=results_dtype)

    if not c_api_timer:
        return results
    else:
        return results, api_time
Example #3
0
def DDsmu_mocks(autocorr,
                cosmology,
                nthreads,
                mu_max,
                nmu_bins,
                binfile,
                RA1,
                DEC1,
                CZ1,
                weights1=None,
                RA2=None,
                DEC2=None,
                CZ2=None,
                weights2=None,
                is_comoving_dist=False,
                verbose=False,
                output_savg=False,
                fast_divide_and_NR_steps=0,
                xbin_refine_factor=2,
                ybin_refine_factor=2,
                zbin_refine_factor=1,
                max_cells_per_dim=100,
                c_api_timer=False,
                isa='fastest',
                weight_type=None):
    """
    Calculate the 2-D pair-counts corresponding to the projected correlation
    function, :math:`\\xi(s, \mu)`. The pairs are counted in bins of
    radial separation and cosine of angle to the line-of-sight (LOS). The
    input positions are expected to be on-sky co-ordinates. This module is
    suitable for calculating correlation functions for mock catalogs.

    If ``weights`` are provided, the resulting pair counts are weighted.  The
    weighting scheme depends on ``weight_type``.

    Returns a numpy structured array containing the pair counts for the
    specified bins.


    .. note:: This module only returns pair counts and not the actual
       correlation function :math:`\\xi(s, \mu)`. See the
       utilities :py:mod:`Corrfunc.utils.convert_3d_counts_to_cf` 
       for computing :math:`\\xi(s, \mu)` from the pair counts.
    
    .. versionadded:: 2.1.0

    Parameters
    ----------
    
    autocorr: boolean, required
        Boolean flag for auto/cross-correlation. If autocorr is set to 1,
        then the second set of particle positions are not required.

    cosmology: integer, required
        Integer choice for setting cosmology. Valid values are 1->LasDamas
        cosmology and 2->Planck cosmology. If you need arbitrary cosmology,
        easiest way is to convert the ``CZ`` values into co-moving distance,
        based on your preferred cosmology. Set ``is_comoving_dist=True``, to
        indicate that the co-moving distance conversion has already been done.

        Choices:
                 1. LasDamas cosmology. :math:`\\Omega_m=0.25`, :math:`\\Omega_\Lambda=0.75`
                 2. Planck   cosmology. :math:`\\Omega_m=0.302`, :math:`\\Omega_\Lambda=0.698`

        To setup a new cosmology, add an entry to the function,
        ``init_cosmology`` in ``ROOT/utils/cosmology_params.c`` and re-install
        the entire package.

    nthreads: integer
        The number of OpenMP threads to use. Has no effect if OpenMP was not
        enabled during library compilation.

    mu_max: double. Must be in range [0.0, 1.0]
        A double-precision value for the maximum cosine of the angular 
        separation from the line of sight (LOS). Here, ``mu`` is defined as
        the angle between ``s`` and ``l``. If :math:`v_1` and :math:`v_2`
        represent the vectors to each point constituting the pair, then
        :math:`s := v_1 - v_2` and :math:`l := 1/2 (v_1 + v_2)`.

        Note: Only pairs with :math:`0 <= \cos(\\theta_{LOS}) < \mu_{max}`
        are counted (no equality).

    nmu_bins: int
        The number of linear ``mu`` bins, with the bins ranging from
        from (0, :math:`\mu_{max}`)
    
    binfile: string or an list/array of floats
        For string input: filename specifying the ``s`` bins for
        ``DDsmu_mocks``. The file should contain white-space separated values
        of (smin, smax) specifying each ``s`` bin wanted. The bins
        need to be contiguous and sorted in increasing order (smallest bins
        come first).

        For array-like input: A sequence of ``s`` values that provides the
        bin-edges. For example,
        ``np.logspace(np.log10(0.1), np.log10(10.0), 15)`` is a valid
        input specifying **14** (logarithmic) bins between 0.1 and 10.0. This
        array does not need to be sorted.         

    RA1: array-like, real (float/double)
        The array of Right Ascensions for the first set of points. RA's
        are expected to be in [0.0, 360.0], but the code will try to fix cases
        where the RA's are in [-180, 180.0]. For peace of mind, always supply
        RA's in [0.0, 360.0].

        Calculations are done in the precision of the supplied arrays.

    DEC1: array-like, real (float/double)
        Array of Declinations for the first set of points. DEC's are expected
        to be in the [-90.0, 90.0], but the code will try to fix cases where
        the DEC's are in [0.0, 180.0]. Again, for peace of mind, always supply
        DEC's in [-90.0, 90.0].

        Must be of same precision type as RA1.

    CZ1: array-like, real (float/double)
        Array of (Speed Of Light * Redshift) values for the first set of
        points. Code will try to detect cases where ``redshifts`` have been
        passed and multiply the entire array with the ``speed of light``.

        If is_comoving_dist is set, then ``CZ1`` is interpreted as the
        co-moving distance, rather than `cz`.

    weights1: array_like, real (float/double), optional
        A scalar, or an array of weights of shape (n_weights, n_positions)
        or (n_positions,). `weight_type` specifies how these weights are used;
        results are returned in the `weightavg` field.  If only one of
        ``weights1`` or ``weights2`` is specified, the other will be set
        to uniform weights.

    RA2: array-like, real (float/double)
        The array of Right Ascensions for the second set of points. RA's
        are expected to be in [0.0, 360.0], but the code will try to fix cases
        where the RA's are in [-180, 180.0]. For peace of mind, always supply
        RA's in [0.0, 360.0].

        Must be of same precision type as RA1/DEC1/CZ1.

    DEC2: array-like, real (float/double)
        Array of Declinations for the second set of points. DEC's are expected
        to be in the [-90.0, 90.0], but the code will try to fix cases where
        the DEC's are in [0.0, 180.0]. Again, for peace of mind, always supply
        DEC's in [-90.0, 90.0].

        Must be of same precision type as RA1/DEC1/CZ1.

    CZ2: array-like, real (float/double)
        Array of (Speed Of Light * Redshift) values for the second set of
        points. Code will try to detect cases where ``redshifts`` have been
        passed and multiply the entire array with the ``speed of light``.

        If is_comoving_dist is set, then ``CZ2`` is interpreted as the
        co-moving distance, rather than `cz`.

        Must be of same precision type as RA1/DEC1/CZ1.

    weights2: array-like, real (float/double), optional
        Same as weights1, but for the second set of positions

    is_comoving_dist: boolean (default false)
        Boolean flag to indicate that ``cz`` values have already been
        converted into co-moving distances. This flag allows arbitrary
        cosmologies to be used in ``Corrfunc``.

    verbose: boolean (default false)
        Boolean flag to control output of informational messages

    output_savg: boolean (default false)
        Boolean flag to output the average ``s`` for each bin. Code will
        run slower if you set this flag. Also, note, if you are calculating
        in single-precision, ``savg`` will suffer from numerical loss of
        precision and can not be trusted. If you need accurate ``savg``
        values, then pass in double precision arrays for the particle
        positions.

    fast_divide_and_NR_steps: integer (default 0)
        Replaces the division in ``AVX`` implementation with an approximate
        reciprocal, followed by ``fast_divide_and_NR_steps`` of Newton-Raphson.
        Can improve runtime by ~15-20% on older computers. Value of 0 uses
        the standard division operation.
    
    (xyz)bin_refine_factor: integer, default is (2,2,1); typically within [1-3]
        Controls the refinement on the cell sizes. Can have up to a 20% impact
        on runtime.

    max_cells_per_dim: integer, default is 100, typical values in [50-300]
        Controls the maximum number of cells per dimension. Total number of
        cells can be up to (max_cells_per_dim)^3. Only increase if ``rpmax`` is
        too small relative to the boxsize (and increasing helps the runtime).

    c_api_timer: boolean (default false)
        Boolean flag to measure actual time spent in the C libraries. Here
        to allow for benchmarking and scaling studies.

    isa: string (default ``fastest``)
        Controls the runtime dispatch for the instruction set to use. Possible
        options are: [``fastest``, ``avx``, ``sse42``, ``fallback``]

        Setting isa to ``fastest`` will pick the fastest available instruction
        set on the current computer. However, if you set ``isa`` to, say,
        ``avx`` and ``avx`` is not available on the computer, then the code
        will revert to using ``fallback`` (even though ``sse42`` might be
        available).

        Unless you are benchmarking the different instruction sets, you should
        always leave ``isa`` to the default value. And if you *are*
        benchmarking, then the string supplied here gets translated into an
        ``enum`` for the instruction set defined in ``utils/defs.h``.

    weight_type: string, optional
        The type of weighting to apply.  One of ["pair_product", None].  Default: None.

    Returns
    --------

    results: Numpy structured array
        A numpy structured array containing [smin, smax, savg, mumax, npairs, weightavg]
        for each separation bin specified in the ``binfile``. If ``output_savg`` is
        not set, then ``savg`` will be set to 0.0 for all bins; similarly for
        ``weightavg``. ``npairs`` contains the number of pairs in that bin and
        can be used to compute the actual :math:`\\xi(s, \mu)` by combining
        with (DR, RR) counts.

    api_time: float, optional
        Only returned if ``c_api_timer`` is set.  ``api_time`` measures only
        the time spent within the C library and ignores all python overhead.
    """
    try:
        from Corrfunc._countpairs_mocks import countpairs_s_mu_mocks as\
            DDsmu_extn
    except ImportError:
        msg = "Could not import the C extension for the on-sky"\
              "pair counter."
        raise ImportError(msg)

    import numpy as np
    from Corrfunc.utils import translate_isa_string_to_enum, fix_ra_dec,\
        return_file_with_rbins, sys_pipes
    from future.utils import bytes_to_native_str

    # Broadcast scalar weights to arrays
    if weights1 is not None:
        weights1 = np.atleast_1d(weights1)
    if weights2 is not None:
        weights2 = np.atleast_1d(weights2)

    # Check if mu_max is scalar
    if not np.isscalar(mu_max):
        msg = "The parameter `mu_max` = {0}, has size = {1}. "\
              "The code is expecting a scalar quantity (and not "\
              "not a list, array)".format(mu_max, np.size(mu_max))
        raise TypeError(msg)

    # Check that mu_max is within (0.0, 1.0]
    if mu_max <= 0.0 or mu_max > 1.0:
        msg = "The parameter `mu_max` = {0}, is the max. of cosine of an "
        "angle and should be within (0.0, 1.0]".format(mu_max)
        raise ValueError(msg)

    if not autocorr:
        if RA2 is None or DEC2 is None or CZ2 is None:
            msg = "Must pass valid arrays for RA2/DEC2/CZ2 for "\
                  "computing cross-correlation"
            raise ValueError(msg)

        # If only one set of points has weights, set the other to uniform weights
        if weights1 is None and weights2 is not None:
            weights1 = np.ones_like(weights2)
        if weights2 is None and weights1 is not None:
            weights2 = np.ones_like(weights1)

    else:
        RA2 = np.empty(1)
        DEC2 = np.empty(1)
        CZ2 = np.empty(1)

    fix_ra_dec(RA1, DEC1)
    if autocorr == 0:
        fix_ra_dec(RA2, DEC2)

    # Passing None parameters breaks the parsing code, so avoid this
    kwargs = {}
    for k in ['weights1', 'weights2', 'weight_type', 'RA2', 'DEC2', 'CZ2']:
        v = locals()[k]
        if v is not None:
            kwargs[k] = v

    integer_isa = translate_isa_string_to_enum(isa)
    sbinfile, delete_after_use = return_file_with_rbins(binfile)
    with sys_pipes():
        extn_results = DDsmu_extn(
            autocorr,
            cosmology,
            nthreads,
            mu_max,
            nmu_bins,
            sbinfile,
            RA1,
            DEC1,
            CZ1,
            is_comoving_dist=is_comoving_dist,
            verbose=verbose,
            output_savg=output_savg,
            fast_divide_and_NR_steps=fast_divide_and_NR_steps,
            xbin_refine_factor=xbin_refine_factor,
            ybin_refine_factor=ybin_refine_factor,
            zbin_refine_factor=zbin_refine_factor,
            max_cells_per_dim=max_cells_per_dim,
            c_api_timer=c_api_timer,
            isa=integer_isa,
            **kwargs)
    if extn_results is None:
        msg = "RuntimeError occurred"
        raise RuntimeError(msg)
    else:
        extn_results, proj, proj_tensor, api_time = extn_results

    if delete_after_use:
        import os
        os.remove(sbinfile)

    results_dtype = np.dtype([(bytes_to_native_str(b'smin'), np.float),
                              (bytes_to_native_str(b'smax'), np.float),
                              (bytes_to_native_str(b'savg'), np.float),
                              (bytes_to_native_str(b'mumax'), np.float),
                              (bytes_to_native_str(b'npairs'), np.uint64),
                              (bytes_to_native_str(b'weightavg'), np.float)])

    nbin = len(extn_results)
    results = np.zeros(nbin, dtype=results_dtype)

    for ii, r in enumerate(extn_results):
        results['smin'][ii] = r[0]
        results['smax'][ii] = r[1]
        results['savg'][ii] = r[2]
        results['mumax'][ii] = r[3]
        results['npairs'][ii] = r[4]
        results['weightavg'][ii] = r[5]

    proj = np.array(proj)
    projt = np.array(proj_tensor)
    # Keep projt as 1d array
    # nprojbins = len(proj)
    # projt = np.zeros((nprojbins, nprojbins))
    # for i in range(nprojbins):
    #     for j in range(nprojbins):
    #         projt[i][j] = proj_tensor[i*nprojbins+j]

    if not c_api_timer:
        return results, proj, projt
    else:
        return results, proj, projt, api_time
def find_fastest_DDtheta_mocks_bin_refs(autocorr, nthreads, binfile,
                                        RA1, DEC1, RA2=None, DEC2=None,
                                        link_in_dec=True, link_in_ra=True,
                                        verbose=False, output_thetaavg=False,
                                        max_cells_per_dim=100,
                                        isa=r'fastest',
                                        maxbinref=3, nrepeats=3,
                                        return_runtimes=False):
    """

    Parameters
    ----------
    autocorr : boolean, required
        Boolean flag for auto/cross-correlation. If autocorr is set to 1,
        then the second set of particle positions are not required.

    nthreads : integer
        Number of threads to use.

    binfile: string or an list/array of floats. Units: degrees.
        For string input: filename specifying the ``theta`` bins for
        ``DDtheta_mocks``. The file should contain white-space separated values
        of (thetamin, thetamax)  for each ``theta`` wanted. The bins need to be
        contiguous and sorted in increasing order (smallest bins come first).

        For array-like input: A sequence of ``theta`` values that provides the
        bin-edges. For example,
        ``np.logspace(np.log10(0.1), np.log10(10.0), 15)`` is a valid
        input specifying **14** (logarithmic) bins between 0.1 and 10.0
        degrees. This array does not need to be sorted.

    RA1 : array-like, real (float/double)
        The array of Right Ascensions for the first set of points. RA1's
        are expected to be in [0.0, 360.0], but the code will try to fix cases
        where the RA1's are in [-180, 180.0]. For peace of mind, always supply
        RA1's in [0.0, 360.0].

        Calculations are done in the precision of the supplied arrays.

    DEC1 : array-like, real (float/double)
        Array of Declinations for the first set of points. DEC1's are expected
        to be in the [-90.0, 90.0], but the code will try to fix cases where
        the DEC1's are in [0.0, 180.0]. Again, for peace of mind, always supply
        DEC1's in [-90.0, 90.0].
        Must be of same precision type as RA1.

    RA2 : array-like, real (float/double)
        The array of Right Ascensions for the second set of points. RA2's
        are expected to be in [0.0, 360.0], but the code will try to fix cases
        where the RA2's are in [-180, 180.0]. For peace of mind, always supply
        RA2's in [0.0, 360.0].
        Must be of same precision type as RA1/DEC1.

    DEC2 : array-like, real (float/double)
        Array of Declinations for the second set of points. DEC2's are expected
        to be in the [-90.0, 90.0], but the code will try to fix cases where
        the DEC2's are in [0.0, 180.0]. Again, for peace of mind, always supply
        DEC2's in [-90.0, 90.0].
        Must be of same precision type as RA1/DEC1.

    verbose : boolean (default false)
        Boolean flag to control output of informational messages

    output_thetaavg : boolean (default false)
        Boolean flag to output the average ``\theta`` for each bin. Code will
        run slower if you set this flag.

        If you are calculating in single-precision, ``thetaavg`` will
        suffer from numerical loss of precision and can not be trusted. If you
        need accurate ``thetaavg`` values, then pass in double precision arrays
        for ``RA/DEC``.

    isa: string, case-insensitive (default ``fastest``)
        Controls the runtime dispatch for the instruction set to use. Options
        are: [``fastest``, ``avx512f``, ``avx``, ``sse42``, ``fallback``]

        Setting isa to ``fastest`` will pick the fastest available instruction
        set on the current computer. However, if you set ``isa`` to, say,
        ``avx`` and ``avx`` is not available on the computer, then the code
        will revert to using ``fallback`` (even though ``sse42`` might be
        available).

        Unless you are benchmarking the different instruction sets, you should
        always leave ``isa`` to the default value. And if you *are*
        benchmarking, then the string supplied here gets translated into an
        ``enum`` for the instruction set defined in ``utils/defs.h``.

    max_cells_per_dim: integer, default is 100, typical values in [50-300]
        Controls the maximum number of cells per dimension. Total number of
        cells can be up to (max_cells_per_dim)^2. Only increase if ``rpmax`` is
        too small relative to the boxsize (and increasing helps the runtime).

    maxbinref: integer (default 3)
        The maximum ``bin refine factor`` to use along each dimension.

        Runtime of module scales as ``maxbinref^2``, so change the value of
        ``maxbinref`` with caution.

        Note that ``max_cells_per_dim`` might need to be increased
        to accommodate really large ``maxbinref``.

    nrepeats: integer (default 3)
        Number of times to repeat the timing for an individual run. Accounts
        for the dispersion in runtimes on computers with multiple user
        processes.

    return_runtimes: boolean (default ``false``)
        If set, also returns the array of runtimes.

    Returns
    -------
    (nRA, nDEC) : tuple of integers
        The combination of ``bin refine factors`` along each dimension that
        produces the fastest code.

    runtimes : numpy structured array

        Only returned if ``return_runtimes`` is set, then the return value
        is a tuple containing ((nRA, nDEC), runtimes). ``runtimes`` is a
        ``numpy`` structured array containing the fields, [``nRA``, ``nDEC``,
        ``avg_runtime``, ``sigma_time``]. Here, ``avg_runtime`` is the
        average time, measured over ``nrepeats`` invocations, spent in
        the python extension. ``sigma_time`` is the dispersion of the
        run times across those ``nrepeats`` invocations.

    Example
    -------
    >>> from __future__ import print_function
    >>> import numpy as np
    >>> import time
    >>> from math import pi
    >>> from os.path import dirname, abspath, join as pjoin
    >>> import Corrfunc
    >>> from Corrfunc.mocks.DDtheta_mocks \
        import find_fastest_DDtheta_mocks_bin_refs
    >>> binfile = pjoin(dirname(abspath(Corrfunc.__file__)),
    ...                 "../mocks/tests/", "angular_bins")
    >>> N = 100000
    >>> nthreads = 4
    >>> seed = 42
    >>> np.random.seed(seed)
    >>> RA1 = np.random.uniform(0.0, 2.0*pi, N)*180.0/pi
    >>> cos_theta = np.random.uniform(-1.0, 1.0, N)
    >>> DEC1 = 90.0 - np.arccos(cos_theta)*180.0/pi
    >>> autocorr = 1
    >>> best, _ = find_fastest_DDtheta_mocks_bin_refs(autocorr, nthreads,\
    ...                                               binfile, RA1, DEC1,\
    ...                                               return_runtimes=True)
    >>> print(best) # doctest:+SKIP
    (2, 1)

    .. note:: Since the result might change depending on the computer,
    doctest is skipped for this function.
    """

    weights1 = None
    weights2 = None
    weight_type = None

    try:
        from Corrfunc._countpairs_mocks import countpairs_theta_mocks as\
            DDtheta_mocks_extn
    except ImportError:
        msg = "Could not import the C extension for the angular "\
              "correlation function for mocks."
        raise ImportError(msg)

    import numpy as np
    from Corrfunc.utils import translate_isa_string_to_enum, fix_ra_dec,\
        return_file_with_rbins, convert_to_native_endian, process_weights
    from future.utils import bytes_to_native_str
    import itertools
    import time

    weights1, weights2 = process_weights(weights1, weights2, RA1, RA2,
                                         weight_type, autocorr)

    # Ensure all input arrays are native endian
    RA1, DEC1, weights1, RA2, DEC2, weights2 = [
        convert_to_native_endian(arr, warn=True) for arr in
        [RA1, DEC1, weights1, RA2, DEC2, weights2]]

    fix_ra_dec(RA1, DEC1)
    if autocorr == 0:
        fix_ra_dec(RA2, DEC2)

    # Passing None parameters breaks the parsing code, so avoid this
    kwargs = {}
    for k in ['weights1', 'weights2', 'weight_type', 'RA2', 'DEC2']:
        v = locals()[k]
        if v is not None:
            kwargs[k] = v

    integer_isa = translate_isa_string_to_enum(isa)
    rbinfile, delete_after_use = return_file_with_rbins(binfile)
    bin_refs = np.arange(1, maxbinref + 1)
    if link_in_ra:
        bin_ref_perms = itertools.product(bin_refs, bin_refs)
        nperms = maxbinref ** 2
    else:
        bin_ref_perms = [(1, binref) for binref in bin_refs]
        nperms = maxbinref

    dtype = np.dtype([(bytes_to_native_str(b'nRA'), np.int),
                      (bytes_to_native_str(b'nDEC'), np.int),
                      (bytes_to_native_str(b'avg_time'), np.float),
                      (bytes_to_native_str(b'sigma_time'), np.float)])
    all_runtimes = np.zeros(nperms, dtype=dtype)
    all_runtimes[:] = np.inf

    if autocorr == 0:
        if RA2 is None or DEC2 is None:
            msg = "Must pass valid arrays for RA2/DEC2 for "\
                  "computing cross-correlation."
            raise ValueError(msg)
    else:
        RA2 = np.empty(1)
        DEC2 = np.empty(1)

    if link_in_ra:
        link_in_dec = True

    if not link_in_dec:
        msg = "Error: Brute-force calculation without any gridding " \
              "is forced, as link_in_dec and link_in_ra are both set " \
              "to False. Please set at least one of link_in_dec, link_in_ra=True " \
              "to enable gridding along DEC or along both RA and DEC."
        raise ValueError(msg)

    if verbose and not link_in_ra:
        msg = "INFO: Since ``link_in_ra`` is not set, only gridding in declination " \
              "Checking with refinements in declination ranging from [1, {}] and a " \
              "maximum of {} bins".format(maxbinref, max_cells_per_dim)
        print(msg)

    for ii, (nRA, nDEC) in enumerate(bin_ref_perms):
        total_runtime = 0.0
        total_sqr_runtime = 0.0

        for _ in range(nrepeats):
            t0 = time.perf_counter()
            extn_results = DDtheta_mocks_extn(autocorr, nthreads, rbinfile,
                                              RA1, DEC1, RA2, DEC2,
                                              link_in_dec=link_in_dec,
                                              link_in_ra=link_in_ra,
                                              verbose=verbose,
                                              output_thetaavg=output_thetaavg,
                                              ra_refine_factor=nRA,
                                              dec_refine_factor=nDEC,
                                              max_cells_per_dim=max_cells_per_dim,
                                              isa=integer_isa)
            t1 = time.perf_counter()

            if extn_results is None:
                msg = "RuntimeError occurred with perms = ({0}, {1})".\
                    format(nRA, nDEC)
                raise ValueError(msg)

            dt = (t1 - t0)
            total_runtime += dt
            total_sqr_runtime += dt * dt

        avg_runtime = total_runtime / nrepeats

        # variance = E(X^2) - E^2(X)
        # disp = sqrt(variance)
        runtime_disp = np.sqrt(total_sqr_runtime / nrepeats -
                               avg_runtime * avg_runtime)

        all_runtimes[ii]['nRA'] = nRA
        all_runtimes[ii]['nDEC'] = nDEC
        all_runtimes[ii]['avg_time'] = avg_runtime
        all_runtimes[ii]['sigma_time'] = runtime_disp

    if delete_after_use:
        import os
        os.remove(rbinfile)

    all_runtimes.sort(order=('avg_time', 'sigma_time'))
    results = (all_runtimes[0]['nRA'],
               all_runtimes[0]['nDEC'])

    optional_returns = return_runtimes
    if not optional_returns:
        ret = results
    else:
        ret = (results,)
        if return_runtimes:
            ret += (all_runtimes,)

    return ret