Interface to ASTRA FBP broken on GPU devices

The ASTRA FBP interface (scico.linop.xray.astra.XRayTransform2D.fbp is broken on GPU devices. This test scripts

import numpy as np
from scico.linop.xray.astra import XRayTransform2D

N = 256
x = np.zeros((N, N))
x[N//4:-N//4, N//4:-N//4] = 1.0

Nproj = 90
angles = np.linspace(0, np.pi, Nproj)
A = XRayTransform2D((N, N), N, 1.0, angles)

y = A(x)
xfbp = A.fbp(y)

print(f"FBP result sum: {np.abs(np.sum(xfbp)):.2e}")

indicates a constant zero result when run on a GPU.

lanl / scico

Interface to ASTRA FBP broken on GPU devices #530