plt.imshow(b.array)
plt.title('Simulated data')
plt.show()
plt.imshow(z.array)
plt.title('Backprojected data')
plt.show()
# Using the test data b, different reconstruction methods can now be set up as
# demonstrated in the rest of this file. In general all methods need an initial
# guess and some algorithm options to be set:
x_init = ImageData(np.zeros(x.shape), geometry=ig)
opt = {'tol': 1e-4, 'iter': 1000}
# First a CGLS reconstruction can be done:
x_CGLS, it_CGLS, timing_CGLS, criter_CGLS = CGLS(x_init, Aop, b, opt)
plt.imshow(x_CGLS.array)
plt.title('CGLS')
plt.show()
plt.semilogy(criter_CGLS)
plt.title('CGLS criterion')
plt.show()
# CGLS solves the simple least-squares problem. The same problem can be solved
# by FISTA by setting up explicitly a least squares function object and using
# no regularisation:
# Create least squares object instance with projector, test data and a constant
# coefficient of 0.5:
# So and show simple backprojection
z = Aop.adjoint(data2)
plt.figure()
plt.imshow(z.subset(horizontal_x=1000).as_array())
plt.show()
plt.figure()
plt.imshow(z.subset(horizontal_y=1000).as_array())
plt.show()
plt.figure()
plt.imshow(z.subset(vertical=100).array)
plt.show()
# Set initial guess for CGLS reconstruction
x_init = ImageData(geometry=ig)
# Run 50-iteration CGLS reconstruction
opt = {'tol': 1e-4, 'iter': 20}
x, it, timing, criter = CGLS(x_init,Aop,data2,opt=opt)
# Display ortho slices of reconstruction
plt.figure()
plt.imshow(x.subset(horizontal_x=1000).as_array())
plt.show()
plt.figure()
plt.imshow(x.subset(horizontal_y=1000).as_array())
plt.show()
plt.figure()
plt.imshow(x.subset(vertical=100).as_array())
plt.show()
print("Run FBPD for least squares plus 1-norm regularisation")
x_fbpd1, it_fbpd1, timing_fbpd1, criter_fbpd1 = FBPD(x_init,
None,
f,
g0,
opt=opt)
plt.imshow(x_fbpd1.subset(horizontal_x=80).array)
plt.title('FBPD LS+1')
plt.colorbar()
plt.show()
# Run CGLS, which should agree with the FISTA least squares
print("Run CGLS for least squares")
x_CGLS, it_CGLS, timing_CGLS, criter_CGLS = CGLS(x_init,
Cop,
padded_data2,
opt=opt)
plt.imshow(x_CGLS.subset(horizontal_x=80).array)
plt.title('CGLS')
plt.colorbar()
plt.show()
# Display all reconstructions and decay of objective function
cols = 4
rows = 1
current = 1
fig = plt.figure()
current = current
a = fig.add_subplot(rows, cols, current)
a.set_title('FISTA LS')
Aall = AstraProjectorMC(ig2d, ag2d, 'gpu')
# Compute and simple backprojction and display one channel as image.
Xbp = Aall.adjoint(data2d)
plt.imshow(Xbp.subset(channel=100).array)
plt.show()
# Set initial guess ImageData with zeros for algorithms, and algorithm options.
x_init = ImageData(
numpy.zeros((num_channels, num_pixels_v, num_pixels_h)),
geometry=ig2d,
dimension_labels=['channel', 'horizontal_y', 'horizontal_x'])
opt_CGLS = {'tol': 1e-4, 'iter': 5}
# Run CGLS algorithm and display one channel.
x_CGLS, it_CGLS, timing_CGLS, criter_CGLS = CGLS(x_init, Aall, data2d,
opt_CGLS)
plt.imshow(x_CGLS.subset(channel=100).array)
plt.title('CGLS')
plt.show()
plt.semilogy(criter_CGLS)
plt.title('CGLS Criterion vs iterations')
plt.show()
# Create least squares object instance with projector, test data and a constant
# coefficient of 0.5. Note it is least squares over all channels.
f = Norm2sq(Aall, data2d, c=0.5)
# Options for FISTA algorithm.
opt = {'tol': 1e-4, 'iter': 100}