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Hello Houjun,</div>
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Thanks for your question.</div>
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It depends on the setting. By default, the execution stream will busily check the pool, so it wastes its underlying core if the pool is empty.</div>
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If so, it competes with other non-Argobots threads.</div>
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To let idle execution streams sleep, Argobots provides a few options:</div>
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1. If you enable the scheduler sleep at configuration time, the ES that uses a builtin scheduler will sleep when it cannot
<span style="background-color:rgb(255, 255, 255);display:inline !important">consecutively </span>find a ready ULT in its associated pools.</div>
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./configure --enable-sched-sleep<br>
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The sleep time is configurable via ABT_SCHED_SLEEP_NSEC=XXX</div>
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ABT_SCHED_SLEEP_NSEC=100 ./a.out<br>
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This implementation is very naive but it is easy for users to try.</div>
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2. If ABT_POOL_FIFO_WAIT is used to create a pool, the ES will timed-wait on an empty pool until a ULT is pushed to that pool.</div>
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<span style="margin:0px;font-size:12pt">Internally, it uses a condition variable, so it is smarter. </span><span style="font-size: 12pt;">This needs some efforts to use (at least you need to change the code).</span></div>
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<span style="margin:0px;font-size:12pt"></span> </div>
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...</div>
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Perhaps you might be interested in the following example.</div>
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<a href="https://github.com/pmodels/argobots/blob/main/examples/profiling/async_engine.c">https://github.com/pmodels/argobots/blob/main/examples/profiling/async_engine.c</a><br>
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The following PR is related. This (indirectly) shows how to check the CPU resource consumption by ESs.</div>
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<a href="https://github.com/pmodels/argobots/pull/208">https://github.com/pmodels/argobots/pull/208</a><br>
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If you have any further questions, please feel free to ask!</div>
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Thanks,</div>
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Shintaro</div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> Houjun Tang via discuss <discuss@lists.argobots.org><br>
<b>Sent:</b> Friday, May 7, 2021 5:25 PM<br>
<b>To:</b> discuss@argobots.org <discuss@argobots.org><br>
<b>Cc:</b> Houjun Tang <htang4@lbl.gov><br>
<b>Subject:</b> [argobots-discuss] Idle Execution Stream</font>
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<div>Hi,</div>
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<div>From what I understand, an Argobots execution stream is mapped to a pthread, and the ULTs are executed by it. What happens when there is no ULT in the ES, does the pthread sleep and wait on a conditional variable until a new ULT is scheduled for execution?
Does it compete with other non-Argobots threads for the CPU resources while idle?<br>
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<div>Thanks,</div>
<div>Houjun Tang</div>
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