def test_distributions():
check_init_args(PDF, ["x", "p"])
check_repr(PDF([1, 2, 3], [0.1, 0.8, 0.1]))
assert (repr(PDF(
[1, 2], [0.4, 0.6])) == "PDF(x=array([1., 2.]), p=array([0.4, 0.6]))")
check_init_args(Uniform, ["low", "high", "integer"])
check_repr(Uniform(1, 3))
check_repr(Uniform(1, 4, integer=True))
assert repr(Uniform(0, 1)) == "Uniform(low=0, high=1)"
assert repr(Uniform(
0, 5, integer=True)) == "Uniform(low=0, high=5, integer=True)"
check_init_args(Gaussian, ["mean", "std"])
check_repr(Gaussian(0, 2))
assert repr(Gaussian(1, 0.1)) == "Gaussian(mean=1, std=0.1)"
check_init_args(Exponential, ["scale", "shift", "high"])
check_repr(Exponential(2.0))
check_repr(Exponential(2.0, shift=0.1))
check_repr(Exponential(2.0, shift=0.1, high=10.0))
assert repr(Exponential(2.0)) == "Exponential(scale=2.0)"
check_init_args(UniformHypersphere, ["surface", "min_magnitude"])
check_repr(UniformHypersphere())
check_repr(UniformHypersphere(surface=True))
check_repr(UniformHypersphere(min_magnitude=0.3))
assert repr(UniformHypersphere()) == "UniformHypersphere()"
assert repr(
UniformHypersphere(surface=True)) == "UniformHypersphere(surface=True)"
check_init_args(Choice, ["options", "weights"])
check_repr(Choice([3, 2, 1]))
check_repr(Choice([3, 2, 1], weights=[0.1, 0.2, 0.7]))
assert repr(Choice([1, 2, 3])) == "Choice(options=array([1., 2., 3.]))"
assert (repr(
Choice([1, 2, 3], weights=[0.1, 0.5, 0.4])
) == "Choice(options=array([1., 2., 3.]), weights=array([0.1, 0.5, 0.4]))")
check_init_args(Samples, ["samples"])
check_repr(Samples([3, 2, 1]))
assert repr(Samples([3, 2, 1])) == "Samples(samples=array([3., 2., 1.]))"
check_init_args(SqrtBeta, ["n", "m"])
check_repr(SqrtBeta(3))
check_repr(SqrtBeta(3, m=2))
assert repr(SqrtBeta(3)) == "SqrtBeta(n=3)"
assert repr(SqrtBeta(3, 2)) == "SqrtBeta(n=3, m=2)"
check_init_args(SubvectorLength, ["dimensions", "subdimensions"])
check_repr(SubvectorLength(6))
check_repr(SubvectorLength(6, 2))
assert repr(SubvectorLength(3)) == "SubvectorLength(dimensions=3)"
check_init_args(CosineSimilarity, ["dimensions"])
check_repr(CosineSimilarity(6))
assert repr(CosineSimilarity(6)) == "CosineSimilarity(dimensions=6)"
def test_cosine_analytical(d, allclose):
pytest.importorskip("scipy") # beta, betainc, betaincinv
dt = 0.0001
x = np.arange(-1 + dt, 1, dt)
def p(x, d):
# unnormalized CosineSimilarity distribution, derived by Eric H.
return (1 - x * x) ** ((d - 3) / 2.0)
dist = CosineSimilarity(d)
pdf_exp = dist.pdf(x)
pdf_act = p(x, d)
cdf_exp = dist.cdf(x)
cdf_act = np.cumsum(pdf_act) / np.sum(pdf_act)
# Check that we get the expected pdf after normalization
assert allclose(pdf_exp / np.sum(pdf_exp), pdf_act / np.sum(pdf_act), atol=0.01)
# Check that this accumulates to the expected cdf
assert allclose(cdf_exp, cdf_act, atol=0.01)
# Check that the inverse cdf gives back x
assert allclose(dist.ppf(cdf_exp), x, atol=0.01)
def test_cosine_sample_shape(seed, allclose):
""""Tests that CosineSimilarity sample has correct shape."""
# sampling (n, d) should be the exact same as sampling (n*d,)
n = 3
d = 4
dist = CosineSimilarity(2)
a = dist.sample(n, d, rng=np.random.RandomState(seed))
b = dist.sample(n * d, rng=np.random.RandomState(seed))
assert allclose(a.flatten(), b)
def test_cosine_intercept(d, p, rng, allclose):
"""Tests CosineSimilarity inverse cdf for finding intercepts."""
pytest.importorskip("scipy") # betaincinv
num_samples = 500
exp_dist = UniformHypersphere(surface=True)
act_dist = CosineSimilarity(d)
dots = exp_dist.sample(num_samples, d, rng=rng)[:, 0]
# Find the desired intercept so that dots >= c with probability p
c = act_dist.ppf(1 - p)
assert allclose(np.sum(dots >= c) / float(num_samples), p, atol=0.05)
def test_cosine_similarity(d, rng):
"""Tests CosineSimilarity sampling."""
num_samples = 2500
num_bins = 8
# Check that it gives a single dimension from UniformHypersphere
exp_dist = UniformHypersphere(surface=True)
act_dist = CosineSimilarity(d)
exp = exp_dist.sample(num_samples, d, rng=rng)[:, 0]
act = act_dist.sample(num_samples, rng=rng)
exp_hist, _ = np.histogram(exp, bins=num_bins)
act_hist, _ = np.histogram(act, bins=num_bins)
assert np.all(np.abs(np.asfarray(exp_hist - act_hist) / num_samples) < 0.15)
def prob_cleanup(similarity, dimensions, vocab_size):
"""Estimate the chance of successful cleanup.
This returns the chance that, out of *vocab_size* randomly chosen
vectors, none of them will be closer to a particular
vector than the value given by *similarity*. To use this, compare
your noisy vector with the ideal vector, pass that value in as
the similarity parameter, and set *vocab_size* to be the number of
competing vectors.
Requires SciPy.
"""
p = CosineSimilarity(dimensions).cdf(similarity)
if similarity < 1. and p == 1.:
raise ArithmeticError(
"Insufficient floating point precision to compute value.")
return p**vocab_size
def test_argreprs():
def check_init_args(cls, args):
assert getfullargspec(cls.__init__).args[1:] == args
def check_repr(obj):
assert eval(repr(obj)) == obj
check_init_args(PDF, ['x', 'p'])
check_repr(PDF([1, 2, 3], [0.1, 0.8, 0.1]))
check_init_args(Uniform, ['low', 'high', 'integer'])
check_repr(Uniform(1, 3))
check_repr(Uniform(1, 4, integer=True))
check_init_args(Gaussian, ['mean', 'std'])
check_repr(Gaussian(0, 2))
check_init_args(Exponential, ['scale', 'shift', 'high'])
check_repr(Exponential(2.))
check_repr(Exponential(2., shift=0.1))
check_repr(Exponential(2., shift=0.1, high=10.))
check_init_args(UniformHypersphere, ['surface', 'min_magnitude'])
check_repr(UniformHypersphere())
check_repr(UniformHypersphere(surface=True))
check_repr(UniformHypersphere(min_magnitude=0.3))
check_init_args(Choice, ['options', 'weights'])
check_repr(Choice([3, 2, 1]))
check_repr(Choice([3, 2, 1], weights=[0.1, 0.2, 0.7]))
check_init_args(Samples, ['samples'])
check_repr(Samples([3, 2, 1]))
check_init_args(SqrtBeta, ['n', 'm'])
check_repr(SqrtBeta(3))
check_repr(SqrtBeta(3, m=2))
check_init_args(SubvectorLength, ['dimensions', 'subdimensions'])
check_repr(SubvectorLength(6))
check_repr(SubvectorLength(6, 2))
check_init_args(CosineSimilarity, ['dimensions'])
check_repr(CosineSimilarity(6))
def test_argreprs():
def check_init_args(cls, args):
assert getfullargspec(cls.__init__).args[1:] == args
def check_repr(obj):
assert eval(repr(obj)) == obj
check_init_args(PDF, ["x", "p"])
check_repr(PDF([1, 2, 3], [0.1, 0.8, 0.1]))
check_init_args(Uniform, ["low", "high", "integer"])
check_repr(Uniform(1, 3))
check_repr(Uniform(1, 4, integer=True))
check_init_args(Gaussian, ["mean", "std"])
check_repr(Gaussian(0, 2))
check_init_args(Exponential, ["scale", "shift", "high"])
check_repr(Exponential(2.0))
check_repr(Exponential(2.0, shift=0.1))
check_repr(Exponential(2.0, shift=0.1, high=10.0))
check_init_args(UniformHypersphere, ["surface", "min_magnitude"])
check_repr(UniformHypersphere())
check_repr(UniformHypersphere(surface=True))
check_repr(UniformHypersphere(min_magnitude=0.3))
check_init_args(Choice, ["options", "weights"])
check_repr(Choice([3, 2, 1]))
check_repr(Choice([3, 2, 1], weights=[0.1, 0.2, 0.7]))
check_init_args(Samples, ["samples"])
check_repr(Samples([3, 2, 1]))
check_init_args(SqrtBeta, ["n", "m"])
check_repr(SqrtBeta(3))
check_repr(SqrtBeta(3, m=2))
check_init_args(SubvectorLength, ["dimensions", "subdimensions"])
check_repr(SubvectorLength(6))
check_repr(SubvectorLength(6, 2))
check_init_args(CosineSimilarity, ["dimensions"])
check_repr(CosineSimilarity(6))
def VTB(n_neurons,
dimensions,
unbind_left=False,
unbind_right=False,
**kwargs):
r"""Compute vector-derived transformation binding (VTB).
VTB uses elementwise addition for superposition. The binding operation
:math:`\mathcal{B}(x, y)` is defined as
.. math::
\mathcal{B}(x, y) := V_y x = \left[\begin{array}{ccc}
V_y' & 0 & 0 \\
0 & V_y' & 0 \\
0 & 0 & V_y'
\end{array}\right] x
with
.. math::
V_y' = d^{\frac{1}{4}} \left[\begin{array}{cccc}
y_1 & y_2 & \dots & y_{d'} \\
y_{d' + 1} & y_{d' + 2} & \dots & y_{2d'} \\
\vdots & \vdots & \ddots & \vdots \\
y_{d - d' + 1} & y_{d - d' + 2} & \dots & y_d
\end{array}\right]
and
.. math:: d'^2 = d.
The approximate inverse :math:`y^+` for :math:`y` is permuting the elements
such that :math:`V_{y^+} = V_y`.
Note that VTB requires the vector dimensionality to be square.
The VTB binding operation is neither associative nor commutative.
Publications with further information are forthcoming.
Parameters
----------
n_neurons : int
Number of neurons to use in each product computation.
dimensions : int
The number of dimensions of the input and output vectors. Needs to be a
square number.
unbind_left : bool
Whether to unbind the left input vector from the right input vector.
unbind_right : bool
Whether to unbind the right input vector from the left input vector.
kwargs : dict
Arguments to pass through to the `nengo.Network` constructor.
Returns
-------
nengo.Network
The newly built product network with attributes:
* **input_left** (`nengo.Node`): The left operand vector to be bound.
* **input_right** (`nengo.Node`): The right operand vector to be
bound.
* **mat** (`nengo.Node`): Representation of the matrix :math:`V_y'`.
* **vec** (`nengo.Node`): Representation of the vector :math:`y`.
* **matmuls** (`list`): Matrix multiplication networks.
* **output** (`nengo.Node`): The resulting bound vector.
"""
sub_d = calc_sub_d(dimensions)
shape_left = (sub_d, sub_d)
shape_right = (sub_d, 1)
with nengo.Network(**kwargs) as net:
net.input_left = nengo.Node(size_in=dimensions)
net.input_right = nengo.Node(size_in=dimensions)
net.output = nengo.Node(size_in=dimensions)
net.mat = nengo.Node(size_in=dimensions)
net.vec = nengo.Node(size_in=dimensions)
if unbind_left and unbind_right:
raise ValueError("Cannot unbind both sides at the same time.")
elif unbind_left:
nengo.Connection(net.input_left,
net.mat,
transform=inversion_matrix(dimensions),
synapse=None)
nengo.Connection(net.input_right,
net.vec,
transform=swapping_matrix(dimensions),
synapse=None)
else:
nengo.Connection(net.input_left, net.vec, synapse=None)
if unbind_right:
tr = inversion_matrix(dimensions)
else:
tr = 1.
nengo.Connection(net.input_right,
net.mat,
transform=tr,
synapse=None)
with nengo.Config(nengo.Ensemble) as cfg:
cfg[nengo.Ensemble].intercepts = CosineSimilarity(dimensions + 2)
cfg[nengo.Ensemble].eval_points = CosineSimilarity(dimensions + 2)
net.matmuls = [
MatrixMult(n_neurons, shape_left, shape_right)
for i in range(sub_d)
]
for i in range(sub_d):
mm = net.matmuls[i]
sl = slice(i * sub_d, (i + 1) * sub_d)
nengo.Connection(net.mat, mm.input_left, synapse=None)
nengo.Connection(net.vec[sl], mm.input_right, synapse=None)
nengo.Connection(mm.output,
net.output[sl],
transform=np.sqrt(sub_d),
synapse=None)
return net
