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<p class="MsoNormal"><span lang="EN-US" style="font-size:10.0pt;font-family:"Verdana",sans-serif;color:#1F497D;mso-fareast-language:EN-US">John,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.0pt;font-family:"Verdana",sans-serif;color:#1F497D;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.0pt;font-family:"Verdana",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Thank you for reporting the bug, it was just typo in the debug assertion statement.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.0pt;font-family:"Verdana",sans-serif;color:#1F497D;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.0pt;font-family:"Verdana",sans-serif;color:#1F497D;mso-fareast-language:EN-US">I have committed the fix without pre-commit review, because it is too trivial typo, I think.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.0pt;font-family:"Verdana",sans-serif;color:#1F497D;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.0pt;font-family:"Verdana",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Thanks,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.0pt;font-family:"Verdana",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Andrey<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.0pt;font-family:"Verdana",sans-serif;color:#1F497D;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif"> openmp-dev-bounces@cs.uiuc.edu [mailto:openmp-dev-bounces@cs.uiuc.edu]
<b>On Behalf Of </b>John Mellor-Crummey<br>
<b>Sent:</b> Monday, July 13, 2015 8:01 PM<br>
<b>To:</b> openmp-dev@dcs-maillist2.engr.illinois.edu<br>
<b>Subject:</b> [Openmp-dev] Bug in OpenMP runtime when compiled in debug mode and exercised using the GNU API<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">I would file this bug with bugzilla, but I can’t figure out where the OpenMP bugs should go. If someone could enlighten me, I’d be grateful.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><b><span style="color:#FF2600">Compiling the simple code below with g++ and linking it to the LLVM OpenMP runtime compiled in debug mode produces a fatal error.</span></b><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><b>The program:</b><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">#include <omp.h><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">#define NUM_THREADS 2<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">int fib(int i)<o:p></o:p></p>
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<p class="MsoNormal">{<o:p></o:p></p>
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<p class="MsoNormal"> if (i < 2) return i;<o:p></o:p></p>
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<p class="MsoNormal"> else return fib(i-1) + fib(i-2);<o:p></o:p></p>
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<p class="MsoNormal">}<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">int main(int argc, char **argv)<o:p></o:p></p>
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<p class="MsoNormal">{<o:p></o:p></p>
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<p class="MsoNormal"> int i, inner_threads;<o:p></o:p></p>
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<p class="MsoNormal"> for (inner_threads = 1; inner_threads <= NUM_THREADS; inner_threads++) {<o:p></o:p></p>
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<p class="MsoNormal">#pragma omp parallel for schedule(runtime) num_threads(inner_threads)<o:p></o:p></p>
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<p class="MsoNormal"> for (i = 0; i < NUM_THREADS; i++) {<o:p></o:p></p>
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<p class="MsoNormal"> fib(10);<o:p></o:p></p>
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<p class="MsoNormal"> }<o:p></o:p></p>
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<p class="MsoNormal"> } <o:p></o:p></p>
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<p class="MsoNormal"> return 0;<o:p></o:p></p>
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<p class="MsoNormal">}<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><b>The error:</b><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Assertion failure at kmp_dispatch.cpp(1392): p_last && p_lb && p_ub && p_st.<o:p></o:p></p>
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<p class="MsoNormal">OMP: Error #13: Assertion failure at kmp_dispatch.cpp(1392).<o:p></o:p></p>
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<p class="MsoNormal">OMP: Hint: Please submit a bug report with this message, compile and run commands used, and machine configuration info including native compiler and operating system versions. Faster response will be obtained by including all program sources.
For information on submitting this issue, please see <a href="http://www.intel.com/software/products/support/">
http://www.intel.com/software/products/support/</a>.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><b>The explanation:</b><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">On line 642 of kmp_gsupport.c, there is a call to <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"> status = KMP_DISPATCH_NEXT(&loc, gtid, NULL, (kmp_int *)p_lb, \<o:p></o:p></p>
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<p class="MsoNormal"> (kmp_int *)p_ub, (kmp_int *)&stride); <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">The NULL is passed to the parameter shown in red below<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">template< typename T ><o:p></o:p></p>
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<p class="MsoNormal">static int<o:p></o:p></p>
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<p class="MsoNormal">__kmp_dispatch_next(<o:p></o:p></p>
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<p class="MsoNormal"> ident_t *loc, int gtid, kmp_int32 <b>*<span style="color:#FF2600">p_last</span>,</b> T *p_lb, T *p_ub, typename traits_t< T >::signed_t *p_st<o:p></o:p></p>
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<p class="MsoNormal">)<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">This always fails the assertion below from line 1392 of kmp_dispatch.c<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"> KMP_DEBUG_ASSERT( <b><span style="color:#FF2600">p_last</span></b> && p_lb && p_ub && p_st ); // AC: these cannot be NULL<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">I could fix it by eliminating the debug assertion, but I think it would be better for someone who understands the kmp dispatching mechanisms to think about how they are being used from the GOMP wrappers.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-size:9.0pt;font-family:Courier;color:black">--<br>
John Mellor-Crummey Professor<br>
Dept of Computer Science Rice University<br>
email: <a href="mailto:johnmc@rice.edu">johnmc@rice.edu</a> phone: 713-348-5179</span><span style="font-size:9.0pt;font-family:"Helvetica",sans-serif;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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