Path: csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!news.glorb.com!news-out.readnews.com!news-xxxfer.readnews.com!news.misty.com!news.iecc.com!.POSTED!nerds-end From: Joshua Cranmer Newsgroups: comp.compilers Subject: Re: Green Compiler ? Date: Thu, 27 Dec 2012 21:59:52 -0600 Organization: A noiseless patient Spider Lines: 28 Sender: johnl@iecc.com Approved: comp.compilers@iecc.com Message-ID: <12-12-026@comp.compilers> References: <12-12-010@comp.compilers> <12-12-013@comp.compilers> NNTP-Posting-Host: news.iecc.com Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Trace: leila.iecc.com 1356708091 39934 64.57.183.58 (28 Dec 2012 15:21:31 GMT) X-Complaints-To: abuse@iecc.com NNTP-Posting-Date: Fri, 28 Dec 2012 15:21:31 +0000 (UTC) Keywords: performance Posted-Date: 28 Dec 2012 10:21:31 EST X-submission-address: compilers@iecc.com X-moderator-address: compilers-request@iecc.com X-FAQ-and-archives: http://compilers.iecc.com Xref: csiph.com comp.compilers:810 On 12/23/2012 3:01 AM, Nils M Holm wrote: > Abid wrote: >> Do we need to change this model and make it >> three dimensional by adding power axis in the search space? > > In principle, I would say that higher execution speed equals more > grenn-ness. Less time spent dissipating heat means less energy > consumed. Power consumption of hardware scales quadratically with respect to frequency. If you can stand doing computation at lower frequency scales (at, say, 600 MHz), you will lose far less energy than doing the equivalent computation at the maximum frequency scale (say, 3 GHz). In general, minimizing power consumption means utilizing all components of your computer most effectively. In current homogeneous computers, the question is rather moot (choice of frequency and cores to run is a decision of the operating system, and compilers generally cannot affect this decision. However, the future of computers seems to be increasing utilization of heterogeneous computation, at which point we're at a point where research into ways of designing code that can take advantage of various unconventional hardware (DSPs, GPUs, etc.) is still ongoing. -- Beware of bugs in the above code; I have only proved it correct, not tried it. -- Donald E. Knuth