def __init__(self, sig, err_lvl, x_true, PSF, recon=False, cmap='Greys',
per_BC=False, per_BC_pad=False, per_t=0.0,
restrict_dom=(None,None)):
"""
class representing a system we wish to invert.
INPUT:
sig - x_true_ftn parameter.
err_lvl - desired noise level (ratio of 100).
x_true - function from functions.py representing the true solution.
PSF - Point Spread Function.
recon - weather or not this is a PSF reconstruction problem.
cmap - matplotlib colormap string name.
per_BC - use periodic boundary condtions?
per_BC_pad - pad the image to apply periodic BC without distortion?
per_t - truncate amount (left, right, top, and bottom).
restrict_dom - 2-tuple index to restrict (left, right) = (top, bottom)
"""
super(Inverse_System_2D, self).__init__()
self.per_BC = per_BC
self.per_BC_pad = per_BC_pad
nx, ny = shape(x_true)
nx = float(nx)
ny = float(ny)
n = nx * ny
hx = 1/nx
hy = 1/ny
if not per_BC:
tx = arange(0, 1, hx)
ty = arange(0, 1, hy)
# A discritization :
if not recon:
A1 = d_psf(tx, hx, PSF(tx, hx, sig=sig))
A2 = d_psf(ty, hy, PSF(ty, hy, sig=sig))
else:
A1 = d_int(tx, hx)
A2 = d_int(ty, hy)
# Set up true solution x_true and data b = A*x_true + error :
Ax = dot(dot(A1, x_true), A2.T)
sigma = err_lvl/100.0 * norm(Ax) / sqrt(n)
eta = sigma * randn(nx, ny)
b = Ax + eta
U1,S1,V1 = svd(A1)
U2,S2,V2 = svd(A2)
S = tensordot(S2, S1, 0)
UTb = dot(dot(U1.T, b), U2)
Vx = dot(V1.T, dot(x_true, V2))
self.A1 = A1
self.A2 = A2
self.U1 = U1
self.U2 = U2
self.V1 = V1
self.V2 = V2
self.S1 = S1
self.S2 = S2
else:
left = -per_t
right = per_t
bottom = -per_t
top = per_t
tx = arange(left, right, hx)
ty = arange(bottom, top, hy)
# A discritization :
if not recon:
X,Y = meshgrid(tx,ty)
ahat = fft2(fftshift(PSF(X, Y, hx, hy, sig=sig)))
else:
print "reconstruction not implemented"
exit(1)
# Set up true solution x_true and data b = A*x_true + error :
l = restrict_dom[0]
r = restrict_dom[1]
Ax = real(ifft2(ahat * fft2(x_true)))
Ax = Ax[l:r, l:r]
x_true = x_true[l:r, l:r]
nx2,ny2 = shape(Ax)
nx2 = float(nx2)
ny2 = float(ny2)
n2 = nx2 * ny2
sigma = err_lvl/100.0 * norm(Ax) / sqrt(n2)
eta = sigma * randn(nx2, ny2)
b = Ax + eta
bhat = fft2(b)
if self.per_BC_pad:
p_d = ((ny/4, ny/4), (nx/4, nx/4))
b_pad = pad(b, p_d, 'constant')
bphat = fft2(b_pad)
DT = pad(ones(ny2), (ny/4, ny/4), 'constant')
D = pad(ones(nx2), (nx/4, nx/4), 'constant')
M = tensordot(DT, D, 0) # mask array
ATDb = real(ifft2(conj(ahat) * fft2(b_pad)))
UTb = bphat
self.D = D
self.DT = DT
self.M = M
self.ATDb = ATDb
self.bphat = bphat
self.b_pad = b_pad
else:
if l is not None and r is not None:
ml = 0.5*(r - l)
mr = 1.5*(r - l)
else:
ml = 0
mr = nx
ahat = ahat[ml:mr, ml:mr]
UTb = bhat
S = abs(ahat)
Vx = fft2(x_true)
self.ahat = ahat
# 2D problems can only be filtered by Tikhonov regularization
self.filt_type = 'Tikhonov'
self.cmap = cmap
self.per_BC = per_BC
self.per_BC_pad = per_BC_pad
self.rng = arange(0, 1, 0.1)
self.n = n
self.nx = nx
self.ny = ny
self.tx = tx
self.ty = ty
self.x_true = x_true
self.Ax = Ax
self.err_lvl = err_lvl
self.sigma = sigma
self.b = b
self.S = S
self.UTb = UTb
self.Vx = Vx
def __init__(self, xi, xf, n, sig, err_lvl, x_true_ftn, PSF, recon=False):
"""
class representing a 1D system we wish to invert.
INPUT:
xi - begin of domain.
xf - end of domain.
n - number of cells.
sig - x_true_ftn parameter.
err_lvl - desired noise level (ratio of 100).
x_true - function from functions.py representing the true solution.
PSF - Point Spread Function for reconstruction problem
recon - weather or not this is a PSF reconstruction problem.
"""
super(Inverse_System_1D, self).__init__()
n = float(n)
omega = xf - xi
h = omega/n
t = arange(xi, xf, h)
# A discritization :
if not recon:
A = d_psf(t, h, PSF(t, h, sig))
else:
A = d_int(t, h)
# Set up true solution x_true and data b = A*x_true + error :
x_true = x_true_ftn(t, h, sig)
Ax = dot(A, x_true)
sigma = err_lvl/100.0 * norm(Ax) / sqrt(n)
eta = sigma * randn(n, 1)
b = Ax + eta.T[0]
x_ls = solve(A,b)
U,S,V = svd(A)
UTb = dot(U.T, b)
# create regularization matrices for GMRF :
diags = [-ones(n+1), ones(n+1)]
D = array(spdiags(diags, [0, 1], n-1, n).todense())
L = dot(D.T, D)
# by default, filter by Tikhonov parameterization
self.filt_type = 'Tikhonov'
self.rng = arange(0, 1, 0.1)
self.omega = omega
self.n = n
self.h = h
self.t = t
self.A = A
self.x_true = x_true
self.x_ls = x_ls
self.Ax = Ax
self.err_lvl = err_lvl
self.sigma = sigma
self.b = b
self.U = U
self.S = S
self.V = V
self.Vx = dot(V, x_true)
self.UTb = UTb
self.D = D
self.L = L
