error when using gpu

Hi this is the part of code which troubles me:

for j=1:length(ZZ)
array(:,index) = A(ZZ(j)+n:ZZ(j)+n+x-1);
index=index+1;
end

The error I get is:

 Undefined function 'colon' for input arguments of type 'parallel.gpu.GPUArray'.

Any help?

Answer 1

[Ben Tordoff]

Unfortunately, an expression like:

gpuArray(1):gpuArray(10)

won't work, and (as Walter says) it looks like one of your ":" expressions involves an argument that is a gpuArray. You have two choices. If you want the result of the ":" to be on the GPU you have to say so explicitly:

tmp = parallel.gpu.GPUArray.colon(ZZ(j)+n, ZZ(j)+n+x-1);
array(:,index) = A(tmp);

If you prefer the result in host memory, gather it first:

tmp = colon(gather(ZZ(j)+n), gather(ZZ(j)+n+x-1));
array(:,index) = A(tmp);

The result should be the same either way, but you may find one faster than the other depending on your data size, hardware and MATLAB release.

Answer 2

[Walter Roberson]

This implies that ZZ or n are located on the GPU, with the result that ZZ(j)+n is a GPU object. The ":" operator cannot deal with GPU objects.