Matrix low size limit

[paoloviviani]

Dear all,
is there a chance that, for matrices smaller than a certain size, MAGMA decides to NOT use the GPU at all and reverts to the CPU lapack implementation (e.g. openblas)?

Thanks in advance,
Paolo

[paoloviviani]

I'm asking this since I'm comparing Openblas ssyevd against Magma ssyevd and I see that, at least until the matrix size is 128x128, the timing are exactly the same, while for bigger matrices the behavior changes.

[mgates3]

Yes, small matrices are simply handed to LAPACK. There is not enough work for the GPU to be efficient and overcome the cost of copying the matrix to the GPU.
-mark