/usr/lib/python3-escript-mpi/esys/downunder/forwardmodels/acoustic.py is in python3-escript-mpi 5.1-5.
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#
# Copyright (c) 2003-2017 by The University of Queensland
# http://www.uq.edu.au
#
# Primary Business: Queensland, Australia
# Licensed under the Apache License, version 2.0
# http://www.apache.org/licenses/LICENSE-2.0
#
# Development until 2012 by Earth Systems Science Computational Center (ESSCC)
# Development 2012-2013 by School of Earth Sciences
# Development from 2014 by Centre for Geoscience Computing (GeoComp)
#
##############################################################################
"""Forward model for acoustic wave forms"""
from __future__ import division, print_function
__copyright__="""Copyright (c) 2003-2017 by The University of Queensland
http://www.uq.edu.au
Primary Business: Queensland, Australia"""
__license__="""Licensed under the Apache License, version 2.0
http://www.apache.org/licenses/LICENSE-2.0"""
__url__="https://launchpad.net/escript-finley"
__all__ = ['AcousticWaveForm']
from .base import ForwardModel
from esys.downunder.coordinates import makeTransformation
from esys.escript import Data, DiracDeltaFunctions, FunctionOnBoundary, hasFeature
from esys.escript.linearPDEs import LinearPDE, SolverOptions
from esys.escript.util import *
import numpy as np
HAVE_DIRECT = hasFeature("PASO_DIRECT") or hasFeature('trilinos')
class AcousticWaveForm(ForwardModel):
"""
Forward Model for acoustic waveform inversion in the frequency domain.
It defines a cost function:
:math: `defect = 1/2 integrate( ( w * ( a * u - data ) ) ** 2 )`
where w are weighting factors, data are the measured data (as a 2-comp
vector of real and imaginary part) for real frequency omega, and u is
the corresponding result produced by the forward model.
u (as a 2-comp vector) is the solution of the complex Helmholtz equation
for frequency omega, source F and complex, inverse, squared p-velocity
sigma:
:math: `-u_{ii} - omega**2 * sigma * u = F`
It is assumed that the exact scale of source F is unknown and the scaling
factor a of F is calculated by minimizing the defect.
"""
def __init__(self, domain, omega, w, data, F, coordinates=None,
fixAtBottom=False, tol=1e-8, saveMemory=True, scaleF=True):
"""
initializes a new forward model with acoustic wave form inversion.
:param domain: domain of the model
:type domain: `Domain`
:param w: weighting factors
:type w: ``Scalar``
:param data: real and imaginary part of data
:type data: ``Data`` of shape (2,)
:param F: real and imaginary part of source given at Dirac points,
on surface or at volume.
:type F: ``Data`` of shape (2,)
:param coordinates: defines coordinate system to be used (not supported yet)
:type coordinates: `ReferenceSystem` or `SpatialCoordinateTransformation`
:param tol: tolerance of underlying PDE
:type tol: positive ``float``
:param saveMemory: if true stiffness matrix is deleted after solution
of PDE to minimize memory requests. This will
require more compute time as the matrix needs to be
reallocated.
:type saveMemory: ``bool``
:param scaleF: if true source F is scaled to minimize defect.
:type scaleF: ``bool``
:param fixAtBottom: if true pressure is fixed to zero at the bottom of
the domain
:type fixAtBottom: ``bool``
"""
super(AcousticWaveForm, self).__init__()
self.__trafo = makeTransformation(domain, coordinates)
if not self.getCoordinateTransformation().isCartesian():
raise ValueError("Non-Cartesian Coordinates are not supported yet.")
if not isinstance(data, Data):
raise ValueError("data must be an escript.Data object.")
if not data.getFunctionSpace() == FunctionOnBoundary(domain):
raise ValueError("data must be defined on boundary")
if not data.getShape() == (2,):
raise ValueError("data must have shape (2,) (real and imaginary part).")
if w is None:
w = 1.
if not isinstance(w, Data):
w = Data(w, FunctionOnBoundary(domain))
else:
if not w.getFunctionSpace() == FunctionOnBoundary(domain):
raise ValueError("Weights must be defined on boundary.")
if not w.getShape() == ():
raise ValueError("Weights must be scalar.")
self.__domain = domain
self.__omega = omega
self.__weight = w
self.__data = data
self.scaleF = scaleF
if scaleF:
A = integrate(self.__weight*length(self.__data)**2)
if A > 0:
self.__data*=1./sqrt(A)
self.__BX = boundingBox(domain)
self.edge_lengths = np.asarray(boundingBoxEdgeLengths(domain))
if not isinstance(F, Data):
F=interpolate(F, DiracDeltaFunctions(domain))
if not F.getShape() == (2,):
raise ValueError("Source must have shape (2,) (real and imaginary part).")
self.__F=Data()
self.__f=Data()
self.__f_dirac=Data()
if F.getFunctionSpace() == DiracDeltaFunctions(domain):
self.__f_dirac=F
elif F.getFunctionSpace() == FunctionOnBoundary(domain):
self.__f=F
else:
self.__F=F
self.__tol=tol
self.__fixAtBottom=fixAtBottom
self.__pde=None
if not saveMemory:
self.__pde=self.setUpPDE()
def getSurvey(self, index=None):
"""
Returns the pair (data, weight)
If argument index is ignored.
"""
return self.__data, self.__weight
def rescaleWeights(self, scale=1., sigma_scale=1.):
"""
rescales the weights such that
:math: integrate( ( w omega**2 * sigma_scale * data * ((1/L_j)**2)**-1) +1 )/(data*omega**2 * ((1/L_j)**2)**-1) * sigma_scale )=scale
:param scale: scale of data weighting factors
:type scale: positive ``float``
:param sigma_scale: scale of 1/vp**2 velocity.
:type sigma_scale: ``Scalar``
"""
raise Warning("rescaleWeights is not tested yet.")
if not scale > 0:
raise ValueError("Value for scale must be positive.")
if not sigma_scale*omega**2*d > 0:
raise ValueError("Rescaling of weights failed due to zero denominator.")
# copy back original weights before rescaling
#self.__weight=[1.*ow for ow in self.__origweight]
L2=1/length(1/self.edge_length)**2
d=Lsup(length(data))
A=integrate(self.__weight*(sigma_scale*omega**2*d+1)/(sigma_scale*omega**2*d) )
if A > 0:
self.__weight*=1./A
if self.scaleF:
self.__data*=sqrt(A)
else:
raise ValueError("Rescaling of weights failed.")
def getDomain(self):
"""
Returns the domain of the forward model.
:rtype: `Domain`
"""
return self.__domain
def getCoordinateTransformation(self):
"""
returns the coordinate transformation being used
:rtype: ``CoordinateTransformation``
"""
return self.__trafo
def setUpPDE(self):
"""
Creates and returns the underlying PDE.
:rtype: `LinearPDE`
"""
if self.__pde is None:
if not HAVE_DIRECT:
raise ValueError("Either this build of escript or the current MPI configuration does not support direct solvers.")
pde=LinearPDE(self.__domain, numEquations=2)
D=pde.createCoefficient('D')
A=pde.createCoefficient('A')
A[0,:,0,:]=kronecker(self.__domain.getDim())
A[1,:,1,:]=kronecker(self.__domain.getDim())
pde.setValue(A=A, D=D)
if self.__fixAtBottom:
DIM=self.__domain.getDim()
z = self.__domain.getX()[DIM-1]
pde.setValue(q=whereZero(z-self.__BX[DIM-1][0])*[1,1])
pde.getSolverOptions().setSolverMethod(SolverOptions.DIRECT)
pde.getSolverOptions().setTolerance(self.__tol)
pde.setSymmetryOff()
else:
pde=self.__pde
pde.resetRightHandSideCoefficients()
return pde
def getSourceScaling(self, u):
"""
returns the scaling factor s required to rescale source F to minimize defect ``|s * u- data|^2``
:param u: value of pressure solution (real and imaginary part)
:type u: ``Data`` of shape (2,)
:rtype: `complex`
"""
uTu = integrate(self.__weight * length(u)**2)
uTar = integrate(self.__weight * ( u[0]*self.__data[0]+u[1]*self.__data[1]) )
uTai = integrate(self.__weight * ( u[0]*self.__data[1]-u[1]*self.__data[0]) )
if uTu > 0:
return complex(uTar/uTu, uTai/uTu)
else:
return complex(1.,0)
def getArguments(self, sigma):
"""
Returns precomputed values shared by `getDefect()` and `getGradient()`.
:param sigma: a suggestion for complex 1/V**2
:type sigma: ``Data`` of shape (2,)
:return: solution, uTar, uTai, uTu
:rtype: ``Data`` of shape (2,), 3 x `float`
"""
pde=self.setUpPDE()
D=pde.getCoefficient('D')
D[0,0]=-self.__omega**2 * sigma[0]
D[0,1]= self.__omega**2 * sigma[1]
D[1,0]=-self.__omega**2 * sigma[1]
D[1,1]=-self.__omega**2 * sigma[0]
pde.setValue(D=D, Y=self.__F, y=self.__f, y_dirac=self.__f_dirac)
u=pde.getSolution()
uTar=integrate(self.__weight * ( u[0]*self.__data[0]+u[1]*self.__data[1]) )
uTai=integrate(self.__weight * ( u[0]*self.__data[1]-u[1]*self.__data[0]) )
uTu = integrate( self.__weight * length(u)**2 )
return u, uTar, uTai, uTu
def getDefect(self, sigma, u, uTar, uTai, uTu):
"""
Returns the defect value.
:param sigma: a suggestion for complex 1/V**2
:type sigma: ``Data`` of shape (2,)
:param u: a u vector
:type u: ``Data`` of shape (2,)
:param uTar: equals `integrate( w * (data[0]*u[0]+data[1]*u[1]))`
:type uTar: `float`
:param uTai: equals `integrate( w * (data[1]*u[0]-data[0]*u[1]))`
:type uTa: `float`
:param uTu: equals `integrate( w * (u,u))`
:type uTu: `float`
:rtype: ``float``
"""
# assuming integrate(w * length(data)**2) =1
if self.scaleF and abs(uTu) >0:
A = 1.-(uTar**2 + uTai**2)/uTu
else:
A = integrate(self.__weight*length(self.__data)**2)- 2 * uTar + uTu
return A/2
def getGradient(self, sigma, u, uTar, uTai, uTu):
"""
Returns the gradient of the defect with respect to density.
:param sigma: a suggestion for complex 1/V**2
:type sigma: ``Data`` of shape (2,)
:param u: a u vector
:type u: ``Data`` of shape (2,)
:param uTar: equals `integrate( w * (data[0]*u[0]+data[1]*u[1]))`
:type uTar: `float`
:param uTai: equals `integrate( w * (data[1]*u[0]-data[0]*u[1]))`
:type uTa: `float`
:param uTu: equals `integrate( w * (u,u))`
:type uTu: `float`
"""
pde=self.setUpPDE()
if self.scaleF and abs(uTu) >0:
Z=((uTar**2+uTai**2)/uTu**2) *interpolate(u, self.__data.getFunctionSpace())
Z[0]+= (-uTar/uTu) * self.__data[0]+ (-uTai/uTu) * self.__data[1]
Z[1]+= (-uTar/uTu) * self.__data[1]+ uTai/uTu * self.__data[0]
else:
Z = u - self.__data
if Z.getFunctionSpace() == DiracDeltaFunctions(self.getDomain()):
pde.setValue(y_dirac=self.__weight * Z)
else:
pde.setValue(y=self.__weight * Z)
D=pde.getCoefficient('D')
D[0,0]=-self.__omega**2 * sigma[0]
D[0,1]=-self.__omega**2 * sigma[1]
D[1,0]= self.__omega**2 * sigma[1]
D[1,1]=-self.__omega**2 * sigma[0]
pde.setValue(D=D)
ZTo2=pde.getSolution()*self.__omega**2
return inner(ZTo2,u)*[1,0]+(ZTo2[1]*u[0]-ZTo2[0]*u[1])*[0,1]
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