Steve, I’m figuring out with Intel the easiest way users can report compiler bugs. -Kumar On Jul 12, 2016, at 1:55 PM, Steven C. Pieper <[email protected]<mailto:[email protected]>> wrote: I have attached a simplified source code and demonstration script to show an OpenMP bug in the Intel Fortran compiler. I am using /soft/compilers/intel_beta/compilers_and_libraries_2017.0.042/linux/bin/intel64/ifort The bug occurs on both the jlse login node and knl00. It occurs using two or more OpenMP threads, but not if only one thread is used. The demonstration uses no optimization (O0) but the bug also happens with optimization. It does not happen on the IBM BG/Q. The bug is a segfault at line 113 of the source file: !$OMP PARALLEL WORKSHARE cof(:,:,1:min(2,num_op_emew),:,:) = 0 cfcl(:,:,:,:) = 0.d0 !$OMP END PARALLEL WORKSHARE It is triggered by line 128 when that line is activated (in the source file it is commented): cof(:,:,2,iqcross(:),1) = cof(:,:,1,iqcross(:),1) + cof(:,:,2,iqcross(:),1) The problem is the index iqcross(:); iqcross is a 2-element array with valid values as are printed. If this line is replaced by the equivalent two lines that follow: cof(:,:,2,iqcross(1),1) = cof(:,:,1,iqcross(1),1) + cof(:,:,2,iqcross(1),1) cof(:,:,2,iqcross(2),1) = cof(:,:,1,iqcross(2),1) + cof(:,:,2,iqcross(2),1) no segfault occurs. Note also that in fact this section of the code will never be reached due to the stop at line 119 and the if at line 121 which is false. In the original large code, this second OMP section was more than 100 lines removed from the first with a large intermediate OMP section. The script first compiles and runs the source with the commented line (bug-ok.f). This shows that things work with the line removed. Then the script uses sed to uncomment the line into bug-bad.f and compiles and runs that. This causes the segfault. Steve -- Steven C. Pieper, Senior Physicist Emeritus: [email protected]<mailto:[email protected]> Argonne National Laboratory, Physics Division, Bldg. 203, Argonne, IL 60439 Phone: 630-252-4232 Fax -6008 Secretary, Debra Beres, -4100 http://www.phy.anl.gov/theory/staff/scp.html <makebug.txt><bug-ok.f>_______________________________________________ Intel-nda mailing list [email protected]<mailto:[email protected]> https://lists.jlse.anl.gov/mailman/listinfo/intel-nda