def push_backward(echoes, voxshift, ivoxshift, extrapolate, out=None):
"""Push echoes "backward" (reversed gradient)"""
if out is None:
out = torch.zeros_like(echoes)
if extrapolate:
if voxshift is None:
if not utils.same_storage(out, echoes):
out.copy_(echoes)
return out
out[0::2] = push1d(echoes[0::2], ivoxshift)
out[1::2] = push1d(echoes[1::2], voxshift)
else:
if voxshift is None:
if not utils.same_storage(out, echoes):
out[1:-1].copy_(echoes[1:-1])
return out
out[2::2] = push1d(echoes[2::2], ivoxshift)
out[1:-1:2] = push1d(echoes[1:-1:2], voxshift)
return out
def push_forward(echoes, voxshift, ivoxshift, out=None):
"""Push echoes "forward" (nonreversed gradient)"""
if out is None:
out = torch.empty_like(echoes)
if voxshift is None:
if not utils.same_storage(out, echoes):
out.copy_(echoes)
return out
out[0::2] = push1d(echoes[0::2], voxshift)
out[1::2] = push1d(echoes[1::2], ivoxshift)
return out
