Re: Parallel computing with Mathematica 7?

*To*: mathgroup at smc.vnet.net*Subject*: [mg95368] Re: Parallel computing with Mathematica 7?*From*: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>*Date*: Sat, 17 Jan 2009 05:26:09 -0500 (EST)*References*: <gkppvv$dsp$1@smc.vnet.net>

Hi, > Does anybody have a positive experience with parallelization in > Mathematica 7? yes, but your example > Timing[ParallelTable[Element,{i,1,2}]] > > where Element = Tr[MatrixExp[A]] and A is a large latrix. is a very stupid one. You can't expect that the distribution of a large matrix A to the kernels will not need the most of the time, while the computation of the expression itself is so quick that you will never see a speed up. Since the master kernel does the most work when it distribute the matrix to the other kernels ( and this is a serial task), you see only this in the processor load. Successful parallelization, i.e., one with a speed up, is a hard work and not a matter of putting Parallel*[] in every possible position. BTW: A parallel program should be slower than a serial one. Only in a few cases this is not the case. Regards Jens einschlag at gmail.com wrote: > I have installed Mathematica 7 on my new laptop (Intel Centrino double > core, Windows XP) and the first thing I tried was the long awaited > parallllllel computing. I have tried different new commands and what I > saw was a black box with input and no output. I could not see any > evidence that parallelization works for me. > > My basic test was to create a table of two equal elements being the > trace of the exponential of a large matrix. One such operation takes 8 > sec., so the sequential computation of the table requires the double > time being 16 sec. Parallelization should reduce the time to 8 sec. > However, this does not happen. Here is the code that I used: > > Timing[ParallelTable[Element,{i,1,2}]] > > where Element = Tr[MatrixExp[A]] and A is a large latrix. > > I have looked at the system performace in the Windows Task Manager. > Both with Table and ParallelTable the processor load was 50%, that is, > only one core of the two was working. > > In addition, I have found that the command Parallelize does not take > the option Method->"..." > > Does anybody have a positive experience with parallelization in > Mathematica 7? Do I have to perform a special setup to get these > features working? I tried different ...Kernel... manipulations to no > avail. > > Dmitry >