A Party to the World » building http://dan.lecocq.us/wordpress Life, love, and computer science Fri, 06 Jan 2012 17:21:19 +0000 en hourly 1 http://wordpress.org/?v=3.2.1 Make With Multiple Cores http://dan.lecocq.us/wordpress/2008/10/11/make-with-multiple-cores/ http://dan.lecocq.us/wordpress/2008/10/11/make-with-multiple-cores/#comments Sun, 12 Oct 2008 03:09:12 +0000 Dan http://dan.lecocq.us/wordpress/2008/10/11/make-with-multiple-cores/ I was building something, and I remembered a friend was saying a while ago that you could tell gcc how many cores to use when building something. I don’t know if that’s true or not, but it turns out you can certainly tell make:

make -j(number of cores to use)

For example,

make -j2

I took a screen capture of System Monitor after building each way (make and make -j2), to see the difference. The first box is using just one core, and the second is using both.

Multicore Make

I had initially thought I’d have to tell gcc, and so I had planned to edit the makefile to automatically find the number of cores on the system, and then run gcc with that as an argument, so I went in search of how to find the number of cores on a Linux system. It turns out the easiest way to get that number that I came across was to use /proc/cpuinfo:

cat /proc/cpuinfo | grep 'cpu cores' | head -1 | sed -r 's/^.+([[:digit:]]+)/1/'

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