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POWhy is R multicore only using one core?
 

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  1. POWhy is R multicore only using one core?
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    <blockquote> <p><strong>Possible Duplicate:</strong><br> <a href="https://stackoverflow.com/questions/12924698/parallel-processing-in-r-limited">Parallel processing in R limited</a> </p> </blockquote> <p>I've written some code in R multicore, and I'm running it on a 24-core machine. In fact there are only 12 cores, but they are hyperthreaded, so it looks like there are 24.</p> <p>Here's what's strange: all the threads run on the same single core! So they each only use a tiny amount of cpu, instead of each running on a single core, and chewing up all available cores.</p> <p>For simplicity, I'm just running 4 threads:</p> <pre><code>mclapply( 1:30, function(size) { # time consuming stuff that is cpu bound (think "forecast.ets" et al) }, mc.cores = 4, mc.preschedule = F ) </code></pre> <p>Prior to running this, there is already an R process running on one core, using 100% of that core's capacity:</p> <p><img src="https://i.stack.imgur.com/Ro14R.png" alt="enter image description here"></p> <p>Next, I launch the "multicore process", and 4 extra threads fight for the same core!:</p> <p><img src="https://i.stack.imgur.com/6OGAu.png" alt="enter image description here"></p> <p>... so, they each get 12% of one core, or about 1% of the available processing power, when they should each be able to get 100% of one core. Also, the other R process now only get 50% of the core.</p> <p>OS is Ubuntu 12.04 64-bit. Hardware is Intel. R is version 2.15.2 "trick or treat"</p> <p>Thoughts? (I know I could just use snowfall, but I have a ton of variables, and I really don't want to have to <code>sfExport</code> all of them!)</p> <p>Edit: oh, I guess there's some global lock somewhere? But still, why would there be a conflict between two completely separate R processes? I can run two R processes in parallel just fine, with each taking 100% of a core's CPU.</p> <p>Edit2: Thanks to Dirk's pointer, I rebuilt openblas, and it's looking much healthier now!:</p> <p><img src="https://i.stack.imgur.com/GSt7H.png" alt="enter image description here"></p>
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    1. COHave you run "registerDC" before "doMC" ?
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    2. COHaven't heard of either, so no, and I will go and find what those are now.
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    3. COHmmm, I'm using the multicore package that comes with R, as the `parallel` package. There doesn't seem to be either of those two functions. Should I be better off downloading the raw `multicore` package instead of using `parallel`?
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