Path: csiph.com!usenet.pasdenom.info!weretis.net!feeder1.news.weretis.net!news.roellig-ltd.de!open-news-network.org!feed.xsnews.nl!fbe002.ams.xsnews.nl!ecngs!feeder.ecngs.de!Xl.tags.giganews.com!border1.nntp.ams.giganews.com!nntp.giganews.com!local2.nntp.ams.giganews.com!nntp.bt.com!news.bt.com.POSTED!not-for-mail NNTP-Posting-Date: Tue, 03 Jun 2014 04:02:20 -0500 Date: Tue, 03 Jun 2014 10:02:20 +0100 From: lipska the kat User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:16.0) Gecko/20121010 Thunderbird/16.0.1 MIME-Version: 1.0 Newsgroups: comp.lang.java.programmer Subject: Re: why running multiple instances of the same program is faster than running single instance? References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Message-ID: Lines: 24 X-Usenet-Provider: http://www.giganews.com X-AuthenticatedUsername: NoAuthUser X-Trace: sv3-2xj7Tqb4MvIi0vSoZsoic7EHNxBUo+4doJ8ai8OJm3G4YfynhUUzkWWEg2XEI6+VgmwX2CvJuKWeqWR!9xXkvyTv2/OicBXpa6HVWnNIyxHFEO0+APXctH43HXsfkpo8fCYYGdPjztOc5S7Izo9s/Q1Z0Ps= X-Complaints-To: abuse@btinternet.com X-DMCA-Complaints-To: abuse@btinternet.com X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly X-Postfilter: 1.3.40 X-Original-Bytes: 2737 Xref: csiph.com comp.lang.java.programmer:28641 On 02/06/14 16:12, www wrote: > Hi: > > We have a software(some code from ours and some from the 3rd party) doing scientific calculation. It runs for several hours for finishing two years calculation. We use linux and it has four CPUs. Our code is not con-current multi-threaded yet. > > We are puzzled that when we run multiple instances on the same linux computer, the run finishes earlier than running singe instance. When we run multiple instances, each instance is independently doing its own two year calculation. For example, one instance is calculating 1980-1981, another instance is calculating 1982-1983, etc. If running single instance for 1980-1981 takes 120 minutes to finish, when running together with other instances, it only needs 100 minutes to finish 1980-1981. > > Any suggestions why this is happening? Thank you very much. > Might it have something to do with the IO overhead of paging? If you have a single process with a given amount of memory that runs for a long time then eventually some paging will occur. If you have multiple processes with a (similar?) given amount of memory then there will be less need for paging, what happens if you increase the heap space of the single process (at least double) and reduce the heap space of the multiple processes (by half) -- lipska the kat - treacherous feline. Proudly nominated for IPOTY 2014 - LIGAF GNU/Linux user #560883 - linuxcounter.net