comp.lang.idl-pvwave archive - RDF feed
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description: Messages from Usenet group comp.lang.idl-pvwave, compiled by Paulo Penteado
items: Re: When does IDL use MPs?

Re: When does IDL use MPs?
type: item
description: Jonathan Greenberg (greenberg@ucdavis.edu) writes: > Do I need to specifically invoke multiprocessor calls in an IDL procedure, > or will it use MPs whenever appropriate? Oh, oh. Those marketing guys have gotten out again. :-( I'm afraid IDL is not multi-threaded. It can use multiprocessors in one very narrowly defined situation: when it is rendering object graphics volumes. Other than that, you can invoke until the cows come home, but it's not going to help much. Prayer would be more effective, I think. :-) Cheers, David -- David W. Fanning, Ph.D. Fanning Software Consulting, Inc. Phone: 970-221-0438, E-mail: david@dfanning.com Coyote's Guide to IDL Programming: http://www.dfanning.com/ Toll-Free IDL Book Orders: 1-888-461-0155
creator: David Fanning
date: 2002-11-13T20:02:45-00:00

Re: When does IDL use MPs?
type: item
description: In article <MPG.183c5dd4dd47868b989a17@news.frii.com>, David Fanning <david@dfanning.com> wrote: > Jonathan Greenberg (greenberg@ucdavis.edu) writes: > >> Do I need to specifically invoke multiprocessor calls in an IDL procedure, >> or will it use MPs whenever appropriate? > > Oh, oh. Those marketing guys have gotten out again. :-( > > I'm afraid IDL is not multi-threaded. It can use > multiprocessors in one very narrowly defined situation: > when it is rendering object graphics volumes. Other > than that, you can invoke until the cows come home, but > it's not going to help much. Prayer would be more > effective, I think. :-) > > Cheers, > > David > What about Chapter 2 in 'What's New in IDL 5.5': 'Muli-Threading in IDL' Page 134 list about 2 dozen functions that support multi-threading. This chapter also answers the original posters question. This file should be the docs directory as a PDF file. --Mike
creator: mchinand
date: 2002-11-13T20:09:33-00:00

Re: When does IDL use MPs?
type: item
description: Mike Chinander (mchinand@midway.uchicago.edu) writes: > What about Chapter 2 in 'What's New in IDL 5.5': > > 'Muli-Threading in IDL' > > Page 134 list about 2 dozen functions that support multi-threading. > > This chapter also answers the original posters question. This file should > be the docs directory as a PDF file. Well, there you go. I'm beginning to understand how Craig feels, as I seem to be completely stuck in IDL 5.4. :-( Cheers, David -- David W. Fanning, Ph.D. Fanning Software Consulting, Inc. Phone: 970-221-0438, E-mail: david@dfanning.com Coyote's Guide to IDL Programming: http://www.dfanning.com/ Toll-Free IDL Book Orders: 1-888-461-0155
creator: David Fanning
date: 2002-11-13T20:21:24-00:00

Re: When does IDL use MPs?
type: item
description: David Fanning <david@dfanning.com> writes: > > Well, there you go. I'm beginning to understand how > Craig feels, as I seem to be completely stuck in IDL 5.4. :-( Umm, but I'm stuck in IDL *5.2* You have no idea how I feel :-) Craig -- ------------------------------------------------------------ -------------- Craig B. Markwardt, Ph.D. EMAIL: craigmnet@cow.physics.wisc.edu Astrophysics, IDL, Finance, Derivatives | Remove "net" for better response ------------------------------------------------------------ --------------
creator: Craig Markwardt
date: 2002-11-14T04:21:06-00:00

Re: When does IDL use MPs?
type: item
description: On Wed, 13 Nov 2002 13:02:45 -0700, David Fanning wrote: > Jonathan Greenberg (greenberg@ucdavis.edu) writes: > >> Do I need to specifically invoke multiprocessor calls in an IDL >> procedure, or will it use MPs whenever appropriate? > > Oh, oh. Those marketing guys have gotten out again. :-( > > I'm afraid IDL is not multi-threaded. It can use multiprocessors in one > very narrowly defined situation: when it is rendering object graphics > volumes. Other than that, you can invoke until the cows come home, but > it's not going to help much. Prayer would be more effective, I think. > :-) > Well, it's slightly better than that. IDL is designed to use its thread pool for a number of the most important operations and routines (WHERE, FFT, basic array arithmetic, etc.) on MP machines whenever appropriate. The bad news is that the overhead for spawning a separate thread to compute, say, the total of a big array is significant, motivating the default choice for the minimum number of elements before threading occurs to be large: help,!CPU,/STRUCTURES ** Structure !CPU, 6 tags, length=24, data length=24: HW_VECTOR LONG 0 VECTOR_ENABLE LONG 0 HW_NCPU LONG 2 TPOOL_NTHREADS LONG 2 TPOOL_MIN_ELTS LONG 100000 TPOOL_MAX_ELTS LONG 0 I.e. unless you're operating on an array with more than 100,000 elements, you are out of luck (TPOOOL_MIN_ELTS). You can change this value globally with the CPU procedure, or hand tune it in the call to any of the 50 or so routines which are threaded, but 100,000 is usually about right. When the magic is right, it really cooks on my dual-processor system: IDL> r=randomu(sd,10000000L) IDL> t=systime(1) & tot=total(r,TPOOL_MIN_ELTS=10000001L) & print,systime(1)-t 0.11507905 IDL> t=systime(1) & tot=total(r,TPOOL_MIN_ELTS=10000000L) & print,systime(1)-t 0.061390042 I find measurable speedups even for 50,000 elements, but it really shines on much larger chunks of data. It also depends on the function, of course. Experiment and see what you find. JD
creator: JD Smith
date: 2002-11-15T22:20:08-00:00