topic Re: Bug in ZGEMM for complex infinity inputs in Intel® oneAPI Math Kernel Library

Bug in ZGEMM for complex infinity inputs

darshan — Thu, 16 Jul 2009 19:09:15 GMT

I am using MKL 10.1.2.024 under Linux on a x86_64 machine.

There appears to be a bug in the MKL implementation of ZGEMM that computes complex(inf, 0) * complex(x, y) to be complex(nan, nan) instead of complex(inf, inf).

The behavior is demonstrated in the attached example program: zgemm_bug_small.cc
which I compiled with: icpc zgemm_bug_small.cc -o zgemm_bug.exe -L$(MKL) -lmkl_intel_lp64 -lmkl_intel_thread -lmkl_core -lmkl_intel_thread -lmkl_core -lguide -lpthread
Notice I used only the static versions of the libraries and hence had to repeat them in order to resolve link-time conflicts.

Running the example outputs:
[user@machine mkl_test]$ ./zgemm_bug.exe
A = {( 1, 1) ( 0, 0) ( 0, 0)}

B = {( inf, 0) ( 1, 1)
( 0, 0) ( 0, 0)
( 0, 0) ( 0, 0)}

A.B computed using ZGEMM:
C = {( nan, nan) ( 0, 2)}

A.B computed using ZDOTU:
C = {( inf, inf) ( 0, 2)}

Notice that the ZDOTU result is what I would expect and contrary to what ZGEMM returns.

Re: Bug in ZGEMM for complex infinity inputs

Gennady_F_Intel — Fri, 17 Jul 2009 07:59:15 GMT

Well, the same output we have win32 with version 10.2.

A.B computed using ZGEMM:

C = {(-1.#IND, -1.#IND) ( 0, 2)}

A.B computed using ZDOTU:

C = {(1.#INF, 1.#INF) ( 0, 2)}

We will check the problem and let you know if any news.

Thanks for the report.

--Gennady

Re: Bug in ZGEMM for complex infinity inputs

darshan — Fri, 17 Jul 2009 14:50:10 GMT

Thank you, much appreciated.

Re: Bug in ZGEMM for complex infinity inputs

Ying_S_Intel — Sat, 18 Jul 2009 06:34:42 GMT

Quoting - darshan

Dear Customer,
Thanks for your report, this issue has been submitted to our internal development tracking database for futher investigation, we will inform you once a new update becomes available.

Here is a bug tracking number for your reference: 200083929.

Thanks,
Ying