Re: Wolfram, meet Stefan and Boltzmann
- To: mathgroup at smc.vnet.net
- Subject: [mg117454] Re: Wolfram, meet Stefan and Boltzmann
- From: DrMajorBob <btreat1 at austin.rr.com>
- 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 so. Mine is a 3-yr-old iMac, but I doubt disk caching is a different procedure here than on MacBooks. Bobby On Fri, 18 Mar 2011 06:00:51 -0500, Uayeb <uayebswinburne at gmail.com> 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 stanford.edu> wrote: >> In article <ilnh9v$ob... at smc.vnet.net>, Roman <rschm... at gmail.com> >> 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 yahoo.com