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<p class="MsoPlainText"><span style="font-family:"Courier New"">We have a problem caused by this ...<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New"">thread 0<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><b><span style="font-size:12.0pt;font-family:"Courier New"">
<span style="color:maroon">while</span> (!<span style="color:green">flag</span>) {</span></b><span style="font-size:12.0pt;font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><b><span style="font-size:12.0pt;font-family:"Courier New"">
<span style="color:green">MPI_Iprobe</span>(<span style="color:green">MPI_ANY_SOURCE</span>,
<span style="color:green">msg</span>-><span style="color:green">Tag</span>, <span style="color:green">
comm</span>, &<span style="color:green">flag</span>, &<span style="color:green">status</span>);</span></b><span style="font-size:12.0pt;font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><b><span style="font-size:12.0pt;font-family:"Courier New""> }</span></b><span style="font-size:12.0pt;font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New"">and thread 1<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><b><span style="font-size:12.0pt;font-family:"Courier New"">
<span style="color:green">status</span> = <span style="color:green">MPI_Send</span>(<span style="color:green">msg</span>-><span style="color:green">Data</span>,
<span style="color:green">msg</span>-><span style="color:green">Length</span>, <span style="color:green">
MPI_UNSIGNED_CHAR</span>, <span style="color:green">msg</span>-><span style="color:green">Dest</span>,</span></b><span style="font-size:12.0pt;font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><b><span style="font-size:12.0pt;font-family:"Courier New"">
<span style="color:green">msg</span>-><span style="color:green">Tag</span>, <span style="color:green">
comm</span>);</span></b><span style="font-size:12.0pt;font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New"">so thread 0 just polls for a message, and thread 1 sends one. We expect thread 1 to block until the message is received, but thread 0, is never returning a true flag so we can’t receive it.<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New"">Is there a reason for this? Are we doing something wrong (multithreaded MPI_IProbe is not entirely safe), or have we found a bug of some kind?<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New"">using mpich2-1.4.1p1 on windows7
<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New"">mpich2-1.5b2 on linux (fedora 17) and both show the same behaviour.<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New"">many thanks<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New"">JB<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New";mso-fareast-language:EN-GB">--
<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New";mso-fareast-language:EN-GB">John Biddiscombe, email:biddisco @.at.@ cscs.ch<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New";mso-fareast-language:EN-GB">http://www.cscs.ch/<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New";mso-fareast-language:EN-GB">CSCS, Swiss National Supercomputing Centre | Tel: +41 (91) 610.82.07<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New";mso-fareast-language:EN-GB">Via Trevano 131, 6900 Lugano, Switzerland | Fax: +41 (91) 610.82.82<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New";mso-fareast-language:EN-GB"><o:p> </o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
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