cilkscreen showing races on reducers

[Aamir_Shafi]

This seems weird, but cilkscreen reports data race on reducer variable. The code, and corresponding output of cilkscreen is shown below.

user@velour:~/tmp/cilk_tests$ cat reducer_test.c

#include

#include

#include

#include

#include

using namespace std;

cilk::reducer_opadd total(0);

int main() {

const int STAT_SIZE = 2;

const int N=10;

cilk_for(int i=0 ; i

total += 1;

}

cout << "total =" << total.get_value() << endl;

return 0;

}

user@velour:~/tmp/cilk_tests$ icpc -g reducer_test.c

user@velour:~/tmp/cilk_tests$ icpc -V

Intel C++ Intel 64 Compiler XE for applications running on Intel 64, Version 12.0.1.107 Build 20101116

Copyright (C) 1985-2010 Intel Corporation. All rights reserved.

user@velour:~/tmp/cilk_tests$ cilkscreen ./a.out

Cilkscreen Race Detector V2.0.0, Build 1113

Race condition on location 0x6024c0

write access at 0x4014a8: (~/aamirshafi/intel/composerxe-2011.1.107/compiler/include/cilk/reducer_opadd.h:320, cilk::reducer_opadd::operator+=+0x30)

read access at 0x4014a2: (~/aamirshafi/intel/composerxe-2011.1.107/compiler/include/cilk/reducer_opadd.h:320, cilk::reducer_opadd::operator+=+0x2a)

called by 0x7f7d6110860d: (__$U2+0x9d)

called by 0x7f7d611083a0: (cilk_for_recursive+0x100)

called by 0x7f7d61108739: (__$U0+0x99)

called by 0x7f7d61108089: (__cilkrts_cilk_for_32+0xf9)

called by 0x400fa1: (~/aamirshafi/tmp/cilk_tests/reducer_test.c:16, main+0x65)

Race condition on location 0x6024c0

write access at 0x4014a8: (~/aamirshafi/intel/composerxe-2011.1.107/compiler/include/cilk/reducer_opadd.h:320, cilk::reducer_opadd::operator+=+0x30)

write access at 0x4014a8: (~/aamirshafi/intel/composerxe-2011.1.107/compiler/include/cilk/reducer_opadd.h:320, cilk::reducer_opadd::operator+=+0x30)

called by 0x7f7d6110860d: (__$U2+0x9d)

called by 0x7f7d611083a0: (cilk_for_recursive+0x100)

called by 0x7f7d61108739: (__$U0+0x99)

called by 0x7f7d61108089: (__cilkrts_cilk_for_32+0xf9)

called by 0x400fa1: (~/aamirshafi/tmp/cilk_tests/reducer_test.c:16, main+0x65)

total =10

2 errors found by Cilkscreen

Cilkscreen suppressed 16 duplicate error messages

Cant tell the version of the cilkscreen since using -v option gives an error. But the cilkview version info is below:

user@velour:~/tmp/cilk_tests$ cilkscreen -v

E:Unable to load ~/aamirshafi/work/install/cilkutil/bin/../lib32/cilkscreen-tool.so: libimf.so: wrong ELF class: ELFCLASS64

user@velour:~/tmp/cilk_tests$ cilkview -v

cilkview v2.0.1049.0

Copyright (c) 2010 Intel Corp. All rights reserved

user@velour:~/tmp/cilk_tests$ uname -a

Linux velour 2.6.29-tps+perfctr+fpufix #1 SMP Sat Sep 4 22:20:28 EDT 2010 x86_64 GNU/Linux

--Aamir

[Brandon_H_Intel]

Hi Aamir,

I can reproduce the problem with Cilkscreen, and I've submitted a problem report to the Cilk Plus team. I'll update the thread when they have any updates.

[Brandon_H_Intel]

If you compile now with the C++ Composer XE 2011 update 8 and get the latest version of the Cilk Plus SDK, this problem should now be resolved.