In this case, Ig does indeed get created as a gpuArray. The general rule is that if a parameter of a function is considered to be "data", then a gpuArray passed as an argument for that parameter causes the computation to be performed on the GPU, and the output is a gpuArray.
In practice, this means that generally outputs of functions called with gpuArray arguments are also gpuArrays, except when either:
- The output is a size or dimension (this is not "data") - so size, numel, ndims for gpuArray data return ordinary MATLAB arrays.
- The input parameter is a size or dimension
As an example of the second case, consider
d = gpuArray(2);
x = magic(7);
result = sum(x, d);
In this case, the second argument to sum is a gpuArray - but the "data" in this case is an ordinary MATLAB array. So, d is automatically converted to an ordinary array (using gather behind the scenes), and the sum occurs on the CPU, and result is an ordinary (non-GPU) MATLAB array.
