topic Did you follow suggestions in Intel® oneAPI Math Kernel Library

dggev deterministic behaviour

Konstantinos_K_ — Fri, 27 Mar 2015 16:19:29 GMT

Hello,

I am using dggev (mkl versions 11.2.1 & 11.2.2) and i notice some non deterministic behaviour concerning eigenvalues near zero and infinite eigenvalues and eigenvectors. I use the parallel mkl version with gomp (not intel omp). I compile my code using gcc 4.4.7. It seems that there are (at least) 2 sets of output that differ in the regions mentioned. I also use mkl allocators to ensure my memory is aligned. It is a rare phainomenon, but still, could you have a look?

Thanks!

Did you follow suggestions

TimP — Fri, 27 Mar 2015 16:56:00 GMT

Did you follow suggestions posted on Intel site? such as

https://software.intel.com/en-us/articles/introduction-to-the-conditional-numerical-reproducibility-cnr

https://software.intel.com/sites/default/files/article/164389/fp-consistency-110212.pdf

If you didn't take precautions against varying data alignments, this might easily happen.

The differences you observe may be well within the uncertainties of your analysis.

I use mkl_malloc mkl_calloc

Konstantinos_K_ — Fri, 27 Mar 2015 17:15:09 GMT

I use mkl_malloc mkl_calloc and mkl_realloc for alignment

a call to mkl_cbwr_get(MKL_CBWR_ALL) returns 0

a call to mkl_cbwr_get(MKL_CBWR_BRANCH) returns 1 (= MKL_CBWR_BRANCH_OFF)

should i set it to AUTO?

I used mkl_cbwr_set(MKL_CBWR

Konstantinos_K_ — Fri, 27 Mar 2015 17:16:50 GMT

I used mkl_cbwr_set(MKL_CBWR_AUTO) but did not work.

what is the diff into these

Gennady_F_Intel — Mon, 30 Mar 2015 05:14:25 GMT

what is the diff into these results? can you give us the example to check the problem?

In the attachment you will

Konstantinos_K_ — Mon, 30 Mar 2015 10:15:29 GMT

In the attachment you will find the matrices in binary format, a description of the problem and 2 output sets that differ.

Cheers!

Konstantinos, we couldn't

Gennady_F_Intel — Thu, 23 Apr 2015 06:12:42 GMT

Konstantinos, we couldn't reproduce the problem on our side. Would you give the test to where you see the problem on your side?