class SOBTfvReductor(BasicObject):
"""Free-velocity Second-Order Balanced Truncation reductor.
See [MS96]_.
Parameters
----------
fom
The full-order |SecondOrderModel| to reduce.
mu
|Parameter values|.
"""
def __init__(self, fom, mu=None):
assert isinstance(fom, SecondOrderModel)
if not isinstance(mu, Mu):
mu = fom.parameters.parse(mu)
assert fom.parameters.assert_compatible(mu)
self.fom = fom
self.mu = mu
self.V = None
self.W = None
self._pg_reductor = None
def reduce(self, r, projection='bfsr'):
"""Reduce using SOBTfv.
Parameters
----------
r
Order of the reduced model.
projection
Projection method used:
- `'sr'`: square root method
- `'bfsr'`: balancing-free square root method (default, since it avoids scaling by
singular values and orthogonalizes the projection matrices, which might make it more
accurate than the square root method)
- `'biorth'`: like the balancing-free square root method, except it biorthogonalizes the
projection matrices
Returns
-------
rom
Reduced-order |SecondOrderModel|.
"""
assert 0 < r < self.fom.order
assert projection in ('sr', 'bfsr', 'biorth')
# compute all necessary Gramian factors
pcf = self.fom.gramian('pc_lrcf', mu=self.mu)
pof = self.fom.gramian('po_lrcf', mu=self.mu)
if r > min(len(pcf), len(pof)):
raise ValueError(
'r needs to be smaller than the sizes of Gramian factors.')
# find necessary SVDs
_, sp, Vp = spla.svd(pof.inner(pcf), lapack_driver='gesvd')
# compute projection matrices
self.V = pcf.lincomb(Vp[:r])
if projection == 'sr':
alpha = 1 / np.sqrt(sp[:r])
self.V.scal(alpha)
elif projection == 'bfsr':
gram_schmidt(self.V, atol=0, rtol=0, copy=False)
elif projection == 'biorth':
gram_schmidt(self.V,
product=self.fom.M,
atol=0,
rtol=0,
copy=False)
self.W = self.V
# find the reduced model
if self.fom.parametric:
fom_mu = self.fom.with_(
**{
op: getattr(self.fom, op).assemble(mu=self.mu)
for op in ['M', 'E', 'K', 'B', 'Cp', 'Cv']
})
else:
fom_mu = self.fom
self._pg_reductor = SOLTIPGReductor(fom_mu, self.W, self.V,
projection == 'biorth')
rom = self._pg_reductor.reduce()
return rom
def reconstruct(self, u):
"""Reconstruct high-dimensional vector from reduced vector `u`."""
return self._pg_reductor.reconstruct(u)
class GenericSOBTpvReductor(BasicObject):
"""Generic Second-Order Balanced Truncation position/velocity reductor.
See [RS08]_.
Parameters
----------
fom
The full-order |SecondOrderModel| to reduce.
mu
|Parameter values|.
"""
def __init__(self, fom, mu=None):
assert isinstance(fom, SecondOrderModel)
if not isinstance(mu, Mu):
mu = fom.parameters.parse(mu)
assert fom.parameters.assert_compatible(mu)
self.fom = fom
self.mu = mu
self.V = None
self.W = None
self._pg_reductor = None
def _gramians(self):
"""Return Gramians."""
raise NotImplementedError
def _projection_matrices_and_singular_values(self, r, gramians):
"""Return projection matrices and singular values."""
raise NotImplementedError
def reduce(self, r, projection='bfsr'):
"""Reduce using GenericSOBTpv.
Parameters
----------
r
Order of the reduced model.
projection
Projection method used:
- `'sr'`: square root method
- `'bfsr'`: balancing-free square root method (default, since it avoids scaling by
singular values and orthogonalizes the projection matrices, which might make it more
accurate than the square root method)
- `'biorth'`: like the balancing-free square root method, except it biorthogonalizes the
projection matrices
Returns
-------
rom
Reduced-order |SecondOrderModel|.
"""
assert 0 < r < self.fom.order
assert projection in ('sr', 'bfsr', 'biorth')
# compute all necessary Gramian factors
gramians = self._gramians()
if r > min(len(g) for g in gramians):
raise ValueError(
'r needs to be smaller than the sizes of Gramian factors.')
# compute projection matrices
self.V, self.W, singular_values = self._projection_matrices_and_singular_values(
r, gramians)
if projection == 'sr':
alpha = 1 / np.sqrt(singular_values[:r])
self.V.scal(alpha)
self.W.scal(alpha)
elif projection == 'bfsr':
gram_schmidt(self.V, atol=0, rtol=0, copy=False)
gram_schmidt(self.W, atol=0, rtol=0, copy=False)
elif projection == 'biorth':
gram_schmidt_biorth(self.V, self.W, product=self.fom.M, copy=False)
# find the reduced model
if self.fom.parametric:
fom_mu = self.fom.with_(
**{
op: getattr(self.fom, op).assemble(mu=self.mu)
for op in ['M', 'E', 'K', 'B', 'Cp', 'Cv']
})
else:
fom_mu = self.fom
self._pg_reductor = SOLTIPGReductor(fom_mu, self.W, self.V,
projection == 'biorth')
rom = self._pg_reductor.reduce()
return rom
def reconstruct(self, u):
"""Reconstruct high-dimensional vector from reduced vector `u`."""
return self._pg_reductor.reconstruct(u)
class SOBTfvReductor(BasicInterface):
"""Free-velocity Second-Order Balanced Truncation reductor.
See [MS96]_.
Parameters
----------
fom
The full-order |SecondOrderModel| to reduce.
"""
def __init__(self, fom):
assert isinstance(fom, SecondOrderModel)
self.fom = fom
self._pg_reductor = None
self.V = None
self.W = None
def reduce(self, r, projection='bfsr'):
"""Reduce using SOBTfv.
Parameters
----------
r
Order of the reduced model.
projection
Projection method used:
- `'sr'`: square root method
- `'bfsr'`: balancing-free square root method (default, since it avoids scaling by
singular values and orthogonalizes the projection matrices, which might make it more
accurate than the square root method)
- `'biorth'`: like the balancing-free square root method, except it biorthogonalizes the
projection matrices
Returns
-------
rom
Reduced-order |SecondOrderModel|.
"""
assert 0 < r < self.fom.order
assert projection in ('sr', 'bfsr', 'biorth')
# compute all necessary Gramian factors
pcf = self.fom.gramian('pc_lrcf')
pof = self.fom.gramian('po_lrcf')
if r > min(len(pcf), len(pof)):
raise ValueError(
'r needs to be smaller than the sizes of Gramian factors.')
# find necessary SVDs
_, sp, Vp = spla.svd(pof.inner(pcf))
# compute projection matrices
self.V = pcf.lincomb(Vp[:r])
if projection == 'sr':
alpha = 1 / np.sqrt(sp[:r])
self.V.scal(alpha)
elif projection == 'bfsr':
self.V = gram_schmidt(self.V, atol=0, rtol=0)
elif projection == 'biorth':
self.V = gram_schmidt(self.V, product=self.fom.M, atol=0, rtol=0)
self.W = self.V
# find the reduced model
self._pg_reductor = SOLTIPGReductor(self.fom, self.W, self.V,
projection == 'biorth')
rom = self._pg_reductor.reduce()
return rom
def reconstruct(self, u):
"""Reconstruct high-dimensional vector from reduced vector `u`."""
return self._pg_reductor.reconstruct(u)
class GenericSOBTpvReductor(BasicInterface):
"""Generic Second-Order Balanced Truncation position/velocity reductor.
See [RS08]_.
Parameters
----------
fom
The system which is to be reduced.
"""
def __init__(self, fom):
assert isinstance(fom, SecondOrderModel)
self.fom = fom
self.V = None
self.W = None
def _gramians(self):
"""Returns gramians."""
raise NotImplementedError
def _projection_matrices_and_singular_values(self, r, gramians):
"""Returns projection matrices and singular values."""
raise NotImplementedError
def reduce(self, r, projection='bfsr'):
"""Reduce using GenericSOBTpv.
Parameters
----------
r
Order of the reduced model.
projection
Projection method used:
- `'sr'`: square root method
- `'bfsr'`: balancing-free square root method (default,
since it avoids scaling by singular values and
orthogonalizes the projection matrices, which might make
it more accurate than the square root method)
- `'biorth'`: like the balancing-free square root method,
except it biorthogonalizes the projection matrices
Returns
-------
rom
Reduced system.
"""
assert 0 < r < self.fom.order
assert projection in ('sr', 'bfsr', 'biorth')
# compute all necessary Gramian factors
gramians = self._gramians()
if r > min(len(g) for g in gramians):
raise ValueError(
'r needs to be smaller than the sizes of Gramian factors.')
# compute projection matrices and find the reduced model
self.V, self.W, singular_values = self._projection_matrices_and_singular_values(
r, gramians)
if projection == 'sr':
alpha = 1 / np.sqrt(singular_values[:r])
self.V.scal(alpha)
self.W.scal(alpha)
elif projection == 'bfsr':
self.V = gram_schmidt(self.V, atol=0, rtol=0)
self.W = gram_schmidt(self.W, atol=0, rtol=0)
elif projection == 'biorth':
self.V, self.W = gram_schmidt_biorth(self.V,
self.W,
product=self.fom.M)
self.pg_reductor = SOLTIPGReductor(self.fom, self.W, self.V,
projection == 'biorth')
rom = self.pg_reductor.reduce()
return rom
def reconstruct(self, u):
"""Reconstruct high-dimensional vector from reduced vector `u`."""
self.pg_reductor.reconstruct(u)
class SOBTfvReductor(BasicInterface):
"""Free-velocity Second-Order Balanced Truncation reductor.
See [MS96]_.
Parameters
----------
fom
The full-order |SecondOrderModel| to reduce.
"""
def __init__(self, fom):
assert isinstance(fom, SecondOrderModel)
self.fom = fom
self._pg_reductor = None
self.V = None
self.W = None
def reduce(self, r, projection='bfsr'):
"""Reduce using SOBTfv.
Parameters
----------
r
Order of the reduced model.
projection
Projection method used:
- `'sr'`: square root method
- `'bfsr'`: balancing-free square root method (default, since it avoids scaling by
singular values and orthogonalizes the projection matrices, which might make it more
accurate than the square root method)
- `'biorth'`: like the balancing-free square root method, except it biorthogonalizes the
projection matrices
Returns
-------
rom
Reduced-order |SecondOrderModel|.
"""
assert 0 < r < self.fom.order
assert projection in ('sr', 'bfsr', 'biorth')
# compute all necessary Gramian factors
pcf = self.fom.gramian('pc_lrcf')
pof = self.fom.gramian('po_lrcf')
if r > min(len(pcf), len(pof)):
raise ValueError('r needs to be smaller than the sizes of Gramian factors.')
# find necessary SVDs
_, sp, Vp = spla.svd(pof.inner(pcf))
# compute projection matrices
self.V = pcf.lincomb(Vp[:r])
if projection == 'sr':
alpha = 1 / np.sqrt(sp[:r])
self.V.scal(alpha)
elif projection == 'bfsr':
self.V = gram_schmidt(self.V, atol=0, rtol=0)
elif projection == 'biorth':
self.V = gram_schmidt(self.V, product=self.fom.M, atol=0, rtol=0)
self.W = self.V
# find the reduced model
self._pg_reductor = SOLTIPGReductor(self.fom, self.W, self.V, projection == 'biorth')
rom = self._pg_reductor.reduce()
return rom
def reconstruct(self, u):
"""Reconstruct high-dimensional vector from reduced vector `u`."""
return self._pg_reductor.reconstruct(u)
class GenericSOBTpvReductor(BasicInterface):
"""Generic Second-Order Balanced Truncation position/velocity reductor.
See [RS08]_.
Parameters
----------
fom
The full-order |SecondOrderModel| to reduce.
"""
def __init__(self, fom):
assert isinstance(fom, SecondOrderModel)
self.fom = fom
self.V = None
self.W = None
self._pg_reductor = None
def _gramians(self):
"""Return Gramians."""
raise NotImplementedError
def _projection_matrices_and_singular_values(self, r, gramians):
"""Return projection matrices and singular values."""
raise NotImplementedError
def reduce(self, r, projection='bfsr'):
"""Reduce using GenericSOBTpv.
Parameters
----------
r
Order of the reduced model.
projection
Projection method used:
- `'sr'`: square root method
- `'bfsr'`: balancing-free square root method (default, since it avoids scaling by
singular values and orthogonalizes the projection matrices, which might make it more
accurate than the square root method)
- `'biorth'`: like the balancing-free square root method, except it biorthogonalizes the
projection matrices
Returns
-------
rom
Reduced-order |SecondOrderModel|.
"""
assert 0 < r < self.fom.order
assert projection in ('sr', 'bfsr', 'biorth')
# compute all necessary Gramian factors
gramians = self._gramians()
if r > min(len(g) for g in gramians):
raise ValueError('r needs to be smaller than the sizes of Gramian factors.')
# compute projection matrices
self.V, self.W, singular_values = self._projection_matrices_and_singular_values(r, gramians)
if projection == 'sr':
alpha = 1 / np.sqrt(singular_values[:r])
self.V.scal(alpha)
self.W.scal(alpha)
elif projection == 'bfsr':
self.V = gram_schmidt(self.V, atol=0, rtol=0)
self.W = gram_schmidt(self.W, atol=0, rtol=0)
elif projection == 'biorth':
self.V, self.W = gram_schmidt_biorth(self.V, self.W, product=self.fom.M)
# find the reduced model
self._pg_reductor = SOLTIPGReductor(self.fom, self.W, self.V, projection == 'biorth')
rom = self._pg_reductor.reduce()
return rom
def reconstruct(self, u):
"""Reconstruct high-dimensional vector from reduced vector `u`."""
return self._pg_reductor.reconstruct(u)
