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#
# Copyright (c) 2003-2016 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 models for 2D MT (TE and TM mode)"""
from __future__ import division, print_function
__copyright__="""Copyright (c) 2003-2016 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__ = ['MT2DModelTEMode', 'MT2DModelTMMode']
from .base import ForwardModel
from esys.downunder.coordinates import makeTransformation
from esys.escript import Data, Scalar, Vector, Function, FunctionOnBoundary, Solution
from esys.escript.linearPDEs import LinearPDE, SolverOptions
from esys.escript.util import *
from math import pi as PI
class MT2DBase(ForwardModel):
"""
Base class for 2D MT forward models. See `MT2DModelTEMode` and
`MT2DModelTMMode` for actual implementations.
"""
def __init__(self, domain, omega, x, Z, eta=None, w0=1., mu=4*PI*1e-7, sigma0=0.01,
airLayerLevel=None, fixAirLayer=False,
coordinates=None, tol=1e-8, saveMemory=False, directSolver=True):
"""
initializes a new forward model.
:param domain: domain of the model
:type domain: `Domain`
:param omega: frequency
:type omega: positive ``float``
:param x: coordinates of measurements
:type x: ``list`` of ``tuple`` with ``float``
:param Z: measured impedance (possibly scaled)
:type Z: ``list`` of ``complex``
:param eta: spatial confidence radius
:type eta: positive ``float`` or ``list`` of positive ``float``
:param w0: confidence factors for meassurements.
:type w0: ``None`` or a list of positive ``float``
:param mu: permeability
:type mu: ``float``
:param sigma0: background conductivity
:type sigma0: ``float``
:param airLayerLevel: position of the air layer from to bottom of the domain. If not set
the air layer starts at the top of the domain
:type airLayerLevel : ``float`` or ``None``
:param fixAirLayer: fix air layer (TM mode)
:type fixAirLayer: ``bool``
: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 the PDE to minimize memory use. This will
require more compute time as the matrix needs to be
reallocated at each iteration.
:type saveMemory: ``bool``
:param directSolver: if true a direct solver (rather than an iterative
solver) will be used to solve the PDE
:type directSolver: ``bool``
"""
super(MT2DBase, self).__init__()
self.__trafo = makeTransformation(domain, coordinates)
if not self.getCoordinateTransformation().isCartesian():
raise ValueError("Non-Cartesian coordinates are not supported yet.")
if len(x) != len(Z):
raise ValueError("Number of data points and number of impedance values don't match.")
if eta is None:
eta = sup(domain.getSize())*0.45
if isinstance(eta, float) or isinstance(eta, int):
eta = [float(eta)]*len(Z)
elif not len(eta) == len(Z):
raise ValueError("Number of confidence radii and number of impedance values don't match.")
if isinstance(w0, float) or isinstance(w0, int):
w0 =[float(w0)]*len(Z)
elif not len(w0) == len(Z):
raise ValueError("Number of confidence factors and number of impedance values don't match.")
self.__domain = domain
self._omega_mu = omega * mu
self._ks=sqrt(self._omega_mu * sigma0 /2.)
xx=Function(domain).getX()
totalS=0
self._Z = [ Scalar(0., Function(domain)), Scalar(0., Function(domain)) ]
self._weight = Scalar(0., Function(domain))
for s in range(len(Z)):
chi = self.getWeightingFactor(xx, 1., x[s], eta[s])
f = integrate(chi)
if f < eta[s]**2 * 0.01 :
raise ValueError("Zero weight (almost) for data point %s. Change eta or refine mesh."%(s,))
w02 = w0[s]/f
totalS += w02
self._Z[0] += chi*Z[s].real
self._Z[1] += chi*Z[s].imag
self._weight += chi*w02/(abs(Z[s])**2)
if not totalS > 0:
raise ValueError("Scaling of weight factors failed as sum is zero.")
DIM = domain.getDim()
z = domain.getX()[DIM-1]
self._ztop= sup(z)
self._zbottom = inf(z)
if airLayerLevel is None:
airLayerLevel=self._ztop
self._airLayerLevel=airLayerLevel
# botton:
mask0=whereZero(z-self._zbottom)
r=mask0* [ exp(self._ks*(self._zbottom -airLayerLevel))*cos(self._ks*(self._zbottom -airLayerLevel)),
exp(self._ks*(self._zbottom -airLayerLevel))*sin(self._ks*(self._zbottom -airLayerLevel))]
#top:
if fixAirLayer:
mask1=whereNonNegative(z-airLayerLevel)
r+=mask1*[ 1, 0 ]
else:
mask1=whereZero(z-self._ztop)
r+=mask1*[ self._ks*(self._ztop-airLayerLevel)+1, self._ks*(self._ztop-airLayerLevel) ]
self._q=(mask0+mask1)*[1,1]
self._r=r
#====================================
self.__tol = tol
self._directSolver = directSolver
self._saveMemory = saveMemory
self.__pde = None
if not saveMemory:
self.__pde = self.setUpPDE()
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):
"""
Return the underlying PDE.
:rtype: `LinearPDE`
"""
if self.__pde is None:
DIM=self.__domain.getDim()
pde=LinearPDE(self.__domain, numEquations=2)
if self._directSolver == True:
pde.getSolverOptions().setSolverMethod(SolverOptions.DIRECT)
D=pde.createCoefficient('D')
A=pde.createCoefficient('A')
pde.setValue(A=A, D=D, q=self._q)
pde.getSolverOptions().setTolerance(self.__tol)
pde.setSymmetryOff()
else:
pde=self.__pde
pde.resetRightHandSideCoefficients()
pde.setValue(X=pde.createCoefficient('X'), Y=pde.createCoefficient('Y'))
return pde
def getWeightingFactor(self, x, wx0, x0, eta):
"""
returns the weighting factor
"""
try:
origin, spacing, NE = x.getDomain().getGridParameters()
cell = [int((x0[i]-origin[i])/spacing[i]) for i in range(2)]
midpoint = [origin[i]+cell[i]*spacing[i]+spacing[i]/2. for i in range(2)]
return wx0 * whereNegative(length(x-midpoint)-eta)
except:
return wx0 * whereNegative(length(x-x0)-eta)
def getArguments(self, x):
"""
Returns precomputed values shared by `getDefect()` and `getGradient()`.
Needs to be implemented in subclasses.
"""
raise NotImplementedError
def getDefect(self, x, Ex, dExdz):
"""
Returns the defect value. Needs to be implemented in subclasses.
"""
raise NotImplementedError
def getGradient(self, x, Ex, dExdz):
"""
Returns the gradient. Needs to be implemented in subclasses.
"""
raise NotImplementedError
class MT2DModelTEMode(MT2DBase):
"""
Forward Model for two dimensional MT model in the TE mode for a given
frequency omega.
It defines a cost function:
* defect = 1/2 integrate( sum_s w^s * ( E_x/H_y - Z_XY^s ) ) ** 2 *
where E_x is the horizontal electric field perpendicular to the YZ-domain,
horizontal magnetic field H_y=1/(i*omega*mu) * E_{x,z} with complex unit
i and permeability mu. The weighting factor w^s is set to
* w^s(X) = w_0^s *
if length(X-X^s) <= eta and zero otherwise. X^s is the location of
impedance measurement Z_XY^s, w_0^s is the level
of confidence (eg. 1/measurement error) and eta is level of spatial
confidence.
E_x is given as solution of the PDE
* -E_{x,ii} - i omega * mu * sigma * E_x = 0
where E_x at top and bottom is set to solution for background field. Homogeneous Neuman
conditions are assumed elsewhere.
"""
def __init__(self, domain, omega, x, Z_XY, eta=None, w0=1., mu=4*PI*1e-7, sigma0=0.01,
airLayerLevel=None, coordinates=None, Ex_top=1, fixAtTop=False,
tol=1e-8, saveMemory=False, directSolver=True):
"""
initializes a new forward model. See base class for a description of
the arguments.
"""
f = -1./(complex(0,1)*omega*mu)
scaledZXY = [ z*f for z in Z_XY ]
super(MT2DModelTEMode, self).__init__(domain=domain, omega=omega, x=x,
Z=scaledZXY, eta=eta, w0=w0, mu=mu, sigma0=sigma0,
airLayerLevel= airLayerLevel, fixAirLayer=False,
coordinates=coordinates, tol=tol, saveMemory=saveMemory, directSolver=directSolver)
def getArguments(self, sigma):
"""
Returns precomputed values shared by `getDefect()` and `getGradient()`.
:param sigma: conductivity
:type sigma: ``Data`` of shape (2,)
:return: Ex_, Ex_,z
:rtype: ``Data`` of shape (2,)
"""
DIM = self.getDomain().getDim()
pde = self.setUpPDE()
D = pde.getCoefficient('D')
f = self._omega_mu * sigma
D[0,1] = -f
D[1,0] = f
A= pde.getCoefficient('A')
A[0,:,0,:]=kronecker(DIM)
A[1,:,1,:]=kronecker(DIM)
pde.setValue(A=A, D=D, r=self._r)
u = pde.getSolution()
return u, grad(u)[:,1]
def getDefect(self, sigma, Ex, dExdz):
"""
Returns the defect value.
:param sigma: a suggestion for conductivity
:type sigma: ``Data`` of shape ()
:param Ex: electric field
:type Ex: ``Data`` of shape (2,)
:param dExdz: vertical derivative of electric field
:type dExdz: ``Data`` of shape (2,)
:rtype: ``float``
"""
x=dExdz.getFunctionSpace().getX()
Ex=interpolate(Ex, x.getFunctionSpace())
u0=Ex[0]
u1=Ex[1]
u01=dExdz[0]
u11=dExdz[1]
scale = self._weight / ( u01**2 + u11**2 )
Z = self._Z
A = integrate(scale * ( (Z[0]**2+Z[1]**2)*(u01**2+u11**2)
+ 2*Z[1]*(u0*u11-u01*u1)
- 2*Z[0]*(u0*u01+u11*u1)
+ u0**2 + u1**2 ))
return A/2
def getGradient(self, sigma, Ex, dExdz):
"""
Returns the gradient of the defect with respect to density.
:param sigma: a suggestion for conductivity
:type sigma: ``Data`` of shape ()
:param Ex: electric field
:type Ex: ``Data`` of shape (2,)
:param dExdz: vertical derivative of electric field
:type dExdz: ``Data`` of shape (2,)
"""
pde=self.setUpPDE()
DIM = self.getDomain().getDim()
x=dExdz.getFunctionSpace().getX()
Ex=interpolate(Ex, x.getFunctionSpace())
u0 = Ex[0]
u1 = Ex[1]
u01 = dExdz[0]
u11 = dExdz[1]
D=pde.getCoefficient('D')
Y=pde.getCoefficient('Y')
X=pde.getCoefficient('X')
A= pde.getCoefficient('A')
A[0,:,0,:]=kronecker(DIM)
A[1,:,1,:]=kronecker(DIM)
f = self._omega_mu * sigma
D[0,1] = f
D[1,0] = -f
Z = self._Z
scale = 1./( u01**2 + u11**2 )
scale2 = scale**2
scale *= self._weight
scale2 *= self._weight
Y[0] = scale * (u0 - u01*Z[0] + u11*Z[1])
Y[1] = scale * (u1 - u01*Z[1] - u11*Z[0])
X[0,1] = scale2 * (2*u01*u11*(Z[0]*u1-Z[1]*u0) \
+ (Z[0]*u0+Z[1]*u1)*(u01**2-u11**2)
- u01*(u0**2 + u1**2))
X[1,1] = scale2 * (2*u01*u11*(Z[1]*u1+Z[0]*u0) \
+ (Z[1]*u0-Z[0]*u1)*(u01**2-u11**2)
- u11*(u0**2 + u1**2))
pde.setValue(A=A, D=D, X=X, Y=Y)
Zstar=pde.getSolution()
return (-self._omega_mu)* (Zstar[1]*u0-Zstar[0]*u1)
class MT2DModelTMMode(MT2DBase):
"""
Forward Model for two-dimensional MT model in the TM mode for a given
frequency omega.
It defines a cost function:
* defect = 1/2 integrate( sum_s w^s * ( rho*H_x/Hy - Z_YX^s ) ) ** 2 *
where H_x is the horizontal magnetic field perpendicular to the YZ-domain,
horizontal magnetic field H_y=1/(i*omega*mu) * E_{x,z} with complex unit
i and permeability mu. The weighting factor w^s is set to
* w^s(X) = w_0^s *
if length(X-X^s) <= eta and zero otherwise. X^s is the location of
impedance measurement Z_XY^s, w_0^s is the level
of confidence (eg. 1/measurement error) and eta is level of spatial
confidence.
H_x is given as solution of the PDE
* -(rho*H_{x,i})_{,i} + i omega * mu * H_x = 0
where H_x at top and bottom is set to solution for background field.
Homogeneous Neuman conditions are assumed elsewhere.
"""
def __init__(self, domain, omega, x, Z_YX, eta=None, w0=1., mu=4*PI*1e-7, sigma0=0.01,
airLayerLevel=None, coordinates=None, tol=1e-8, saveMemory=False,
directSolver=True):
"""
initializes a new forward model. See base class for a description of
the arguments.
"""
super(MT2DModelTMMode, self).__init__(domain=domain, omega=omega, x=x,
Z=Z_YX, eta=eta, w0=w0, mu=mu, sigma0=sigma0,
airLayerLevel=airLayerLevel, fixAirLayer=True,
coordinates=coordinates, tol=tol,saveMemory=saveMemory, directSolver=directSolver)
def getArguments(self, rho):
"""
Returns precomputed values shared by `getDefect()` and `getGradient()`.
:param rho: resistivity
:type rho: ``Data`` of shape (2,)
:return: Hx, grad(Hx)
:rtype: ``tuple`` of ``Data``
"""
DIM = self.getDomain().getDim()
pde = self.setUpPDE()
D = pde.getCoefficient('D')
f = self._omega_mu
D[0,1] = -f
D[1,0] = f
A= pde.getCoefficient('A')
for i in range(DIM):
A[0,i,0,i]=rho
A[1,i,1,i]=rho
pde.setValue(A=A, D=D, r=self._r)
u = pde.getSolution()
return u, grad(u)
def getDefect(self, rho, Hx, g_Hx):
"""
Returns the defect value.
:param rho: a suggestion for resistivity
:type rho: ``Data`` of shape ()
:param Hx: magnetic field
:type Hx: ``Data`` of shape (2,)
:param g_Hx: gradient of magnetic field
:type g_Hx: ``Data`` of shape (2,2)
:rtype: ``float``
"""
x = g_Hx.getFunctionSpace().getX()
Hx = interpolate(Hx, x.getFunctionSpace())
u0 = Hx[0]
u1 = Hx[1]
u01 = g_Hx[0,1]
u11 = g_Hx[1,1]
scale = rho / ( u0**2 + u1**2 )
Z = self._Z
A = integrate(self._weight * ( Z[0]**2 + Z[1]**2
+ scale*(-2*Z[0]*(u0*u01 + u1*u11)
+2*Z[1]*(u1*u01 - u0*u11)
+rho*(u01**2 + u11**2)) ))
return A/2
def getGradient(self, rho, Hx, g_Hx):
"""
Returns the gradient of the defect with respect to resistivity.
:param rho: a suggestion for resistivity
:type rho: ``Data`` of shape ()
:param Hx: magnetic field
:type Hx: ``Data`` of shape (2,)
:param g_Hx: gradient of magnetic field
:type g_Hx: ``Data`` of shape (2,2)
"""
pde=self.setUpPDE()
DIM = self.getDomain().getDim()
x=g_Hx.getFunctionSpace().getX()
Hx=interpolate(Hx, x.getFunctionSpace())
u0 = Hx[0]
u1 = Hx[1]
u00 = g_Hx[0,0]
u10 = g_Hx[1,0]
u01 = g_Hx[0,1]
u11 = g_Hx[1,1]
A=pde.getCoefficient('A')
D=pde.getCoefficient('D')
Y=pde.getCoefficient('Y')
X=pde.getCoefficient('X')
for i in range(DIM):
A[0,i,0,i]=rho
A[1,i,1,i]=rho
f = self._omega_mu
D[0,1] = f
D[1,0] = -f
Z = self._Z
scale = 1./( u0**2 + u1**2 )
scale2 = scale**2
scale *= self._weight
scale2 *= rho*self._weight
rho_scale = rho*scale
gscale = u01**2 + u11**2
Y[0] = scale2 * ( (Z[0]*u01+Z[1]*u11)*(u0**2-u1**2)
+ 2*u0*u1*(Z[0]*u11-Z[1]*u01)
- rho*u0*gscale )
Y[1] = scale2 * ( (Z[0]*u11-Z[1]*u01)*(u1**2-u0**2)
+ 2*u0*u1*(Z[0]*u01+Z[1]*u11)
- rho*u1*gscale )
X[0,1] = rho_scale * (-Z[0]*u0 + Z[1]*u1 + rho*u01)
X[1,1] = rho_scale * (-Z[0]*u1 - Z[1]*u0 + rho*u11)
pde.setValue(A=A, D=D, X=X, Y=Y)
g=grad(pde.getSolution())
Hstarr_x = g[0,0]
Hstari_x = g[1,0]
Hstarr_z = g[0,1]
Hstari_z = g[1,1]
return -scale*(u0*(Z[0]*u01+Z[1]*u11)+u1*(Z[0]*u11-Z[1]*u01)-rho*gscale)\
- Hstarr_x*u00 - Hstarr_z*u01 - Hstari_x*u10 - Hstari_z*u11
|