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Re: Wolfram, meet Stefan and Boltzmann

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  • Subject: [mg117454] Re: Wolfram, meet Stefan and Boltzmann
  • From: DrMajorBob <btreat1 at>
  • Date: Sat, 19 Mar 2011 05:18:26 -0500 (EST)

Nice try, but several of us with Macs have reported times of 2 seconds or  

Mine is a 3-yr-old iMac, but I doubt disk caching is a different procedure  
here than on MacBooks.


On Fri, 18 Mar 2011 06:00:51 -0500, Uayeb <uayebswinburne at> wrote:

> Considering Daniel's comments about needing to load som .mx files, and
> some of my own experience with Mathematica and other packages, I'll
> hazard a guess that this is because of Mac OS X's disk caching.
> As an example, I use IDL a fair bit (not particularly because I like
> it, but because a lot of astronomy code is already in IDL). In the
> process of reducing astronomical datasets, I often call IDL from the
> command line over and over to do various steps of the reduction. Each
> time, IDL is loaded from scratch (terribly inefficient, I know, but
> faster than me rewriting my code). The first time it is called, it
> often takes some seconds to load, however, all the subsequent
> invocations are much faster (under 1 second).
> I have always assumed this is because of Mac OS X's disk caching
> mechanism. When a file is requested from disk, the contents of the
> file are loaded into free ram so that any subsequent request for the
> file is handled from ram rather than from disk. (This ram usage is
> labeled "Inactive" in activity monitor, from my understanding, and is
> dumped as soon as an application requests more ram).
> A speed consious user will also note that for a file being regularly
> accessed, putting the file on a "Ram disk" often has little, if any,
> speed improvement than leaving it on a physical disk, except for the
> first access.
> My guess, therefore, is that most of us using Mathematica on a regular
> basis, will not see the associated speed delay AES is mentioning even
> if we quit Mathematica because many of the relevant files are still
> cached in ram. In previous (non-Mathematica=96Word loading times,
> actually) discussions of application performance, my understanding is
> that the only way to eliminate the OS caching impacting your results
> is to run the test on a freshly restarted machine.
> Unless I've missed it, AES has not commented on whether subsequent
> evaluations of the integral are any faster, or if this happens
> everytime s/he restarts the kernal, which might be more interesting.
> Afterall, much of the performance of a modern computer is wrapped up
> in all the various levels of caching, mostly because much of what we
> want to do is the same or very similar to what we have just done. So a
> purely unchaced senario is not particularly representative.
> Cheers,
> Andy
> On Mar 16, 10:39 pm, AES <sieg... at> wrote:
>> In article <ilnh9v$ob... at>, Roman <rschm... at>
>> wrote:
>> > AES,
>> > mine is taking 18 seconds as well, and I have a MacBook as well. Maybe
>> > a Mac hardware thing?
>> Thanks for confirmation.
>> For the record, I'm absolutely not pushing any agenda here -- just
>> curious.  Macs and Mathematica do many things so blazingly fast it's
>> near unbelievable.  And this seems like a relatively simple, smooth
>> integral using only simple, smooth, commonplace functions.  So why does
>> evaluating it take so long?

DrMajorBob at

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