# Matlab processing time

dhlucke

March 5, 2002 8:02:33 PM

I've been sitting here all day waiting for this damn numeric integration to finish. It's really starting to kill me.

There's only so much time I can waste on THGC...

So my question is, how big a difference does anyone notice each time they upgrade? I'm currently doing only a trillion steps and I would think it would go a lot faster than this. Running at a Ghz it shouldn't take this long at all. How big a difference would another Ghz make?

<font color=red>If you were to have sex with your clone would that be considered incest or masturbation?</font color=red>

There's only so much time I can waste on THGC...

So my question is, how big a difference does anyone notice each time they upgrade? I'm currently doing only a trillion steps and I would think it would go a lot faster than this. Running at a Ghz it shouldn't take this long at all. How big a difference would another Ghz make?

<font color=red>If you were to have sex with your clone would that be considered incest or masturbation?</font color=red>

More about : matlab processing time

FatBurger

March 5, 2002 8:39:15 PM

Raystonn

March 5, 2002 8:41:35 PM

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dhlucke

March 5, 2002 11:30:08 PM

I'm basically just numerically integrating a function that can't be integrated any other way. The problem is that the numbers are both HUGE and TINY, and I have to add up a series of calculations in a matrix that really should have as many entries as possible. So first I'm creating this matrix and then I have to add up all these massive and tiny numbers. Anything under a million calculations gives me an incomplete result. I'm trying for a trillion, but that takes way too long considering I run the program a number of times with different variables each time.

I have no idea if Matlab is optimized for a specific processor or dual processors.

<font color=red>If you were to have sex with your clone would that be considered incest or masturbation?</font color=red>

Raystonn

March 5, 2002 11:34:05 PM

-Raystonn

= The views stated herein are my personal views, and not necessarily the views of my employer. =

dhlucke

March 5, 2002 11:34:13 PM

AMD_Man

March 5, 2002 11:38:15 PM

AMD technology + Intel technology = Intel/AMD Pentathlon IV; the <b>ULTIMATE</b> PC processor

Kelledin

March 6, 2002 1:55:57 AM

If it's BCD math, you'll need integer processing power more than anything. If matlab uses floating-point math extensively, the range and precision required is liable to force it to forego SSE/SSE2 and use 80-bit floating point instead (in which case, you need an Athlon or an Alpha).

<i>If a server crashes in a server farm and no one pings it, does it still cost four figures to fix?<P ID="edit"><FONT SIZE=-1><EM>Edited by kelledin on 03/05/02 09:57 PM.</EM></FONT></P>

FatBurger

March 6, 2002 1:56:11 AM

I'd tend to agree with Raystonn on getting a 1.6A and overclocking it.

Mines at a 55% overclock at the moment, retail heatsink.

If you like, I can run part of the program (or a similar program), and tell you how fast it is?

<font color=orange>Quarter</font color=orange> <font color=blue>Pounder</font color=blue> <font color=orange>Inside</font color=orange>

Don't step in the sarcasm!

Schmide

March 6, 2002 3:41:30 AM

What matrices are you solving?

Matisaro

March 6, 2002 3:42:58 AM

dhlucke

March 6, 2002 3:48:31 AM

My result is supposed to be something between 10^49 and 10^39.

I think I'll take Fatburger up on his offer and send it to him since the program is tiny but repetitious. It will be interesting if it's a nice boost in speed.

First I sleep though. G'night.

<font color=red>If you were to have sex with your clone would that be considered incest or masturbation?</font color=red>

Matisaro

March 6, 2002 4:17:04 AM

ath0mps0

March 6, 2002 4:25:42 AM

Matisaro

March 6, 2002 4:33:13 AM

jeffg007

March 6, 2002 2:04:37 PM

FatBurger

March 6, 2002 3:31:18 PM

dhlucke

March 7, 2002 1:44:08 AM

FatBurger

March 7, 2002 3:20:58 AM

dhlucke

March 7, 2002 3:45:59 AM

<font color=red>If you were to have sex with your clone would that be considered incest or masturbation?</font color=red>

kief

March 7, 2002 11:53:29 PM

dhlucke

March 8, 2002 12:20:04 AM

Back to my Matlab dilemma...

I have to integrate from 0 to 912E-8, but since I would then be dividing by zero I was just going to do it from some insanely small number to 912E-8. Matlab won't let me go any smaller than 1E-6 on my lower limit though due to some kind of recursion problem. Thus, my lower limit can't get any smaller than my upper limit. I'm stuck for the time being, but my calculation time is down to less than a second with my new found code. My other option is to integrate from 912E-8 to infinity, but that isn't any nicer.

<font color=red>If you were to have sex with your clone would that be considered incest or masturbation?</font color=red>

digikid

March 21, 2002 7:20:00 AM

The problem is that the numbers are both HUGE and TINY...

---------------------------------------------------------

The first thing our comp.sci. prof told us was that the algorithm has to be efficient, the machine doesn't matter. "You can always buy a machine that's twice as fast!", he said.

The hardest thing is to write an efficient algorithm, and for a loop of over 10^12 iterations, this is definitely your problem. Then there's the question whether you should try and solve this yourself, or if you should rely on people who has worked intensively on algorithms in numerical math and written optimized code. I suggest you take a look at what's available. I have such a suggestion here (below). Numerical integration has so many pit-falls, and only certain integration methods work for stiff problems, some only for linear problems, etc.

As for your problem: HUGE and TINY numbers in a numerical integration: sounds like a "stiff differential equation"; is this right? In that case, there is a very good piece of code available from LLNL (Lawrence Livermore Natl. Labs), called LSODA, which is part of the Ordinary Diff. Eqn. package ODEPACK (http://www.llnl.gov/CASC/odepack/). This code is written in Fortran, so I hope you have Linux, or perhaps a Fortran compiler for your OS.

LSODA (and similarily LSODE) solves STIFF ODE's, and automatically determines whether in fact your problem is stiff or not. Easy to run, and very fast.

As far as MATLAB is concerned: love it, great for fast implementation of all sorts of num. math stuff, but don't use it for big for-loops. Of course, if you vectorize your code, MATLAB is great, but Fortran 90 can do that, too! Loops, however, use Fortran for scientific computation: easy and fast. Matlab is interpreted code: it does line-by-line, and cannot compete with Fortran. I have tested loops on the two and found a speed increase with Fortran of over i-don't-even-wanna-say-it times faster.

I can give you more info on LSODA if this is of any help to you.

digikid

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