Linked Questions

602 votes
19 answers
156k views

Where can I find examples of good Mathematica programming practice?

I consider myself a pretty good Mathematica programmer, but I'm always looking out for ways to either improve my way of doing things in Mathematica, or to see if there's something nifty that I haven't ...
56 votes
1 answer
5k views

Why won't Parallelize speed up my code?

What reasons are there that can cause parallelized Mathematica code not to run with full performance?
Szabolcs's user avatar
  • 234k
19 votes
2 answers
1k views

MapThread and parallel computing

This time I have a very short question. Is there a deeper reason why ParallelMapThread does not exist? Regards, Frink
RMMA's user avatar
  • 2,680
13 votes
4 answers
4k views

Why is ParallelTable slower than Table?

Update Following a comment of Szabolcs have changed Timing to AbsoluteTiming. The results are virtually the same. Original post I have accidentally observed the following surprising result. So, why ...
Dr. Wolfgang Hintze's user avatar
15 votes
3 answers
839 views

Why is this parallel evaluation with Dispatch[] so slow?

Can you efficiently parallelize this? The parallel versions are much slower than the sequential version, and I'm not sure why. Does SetSharedVariable allow ...
Michael Hale's user avatar
  • 2,313
12 votes
2 answers
937 views

ParallelMap vs Map performance comparsion

The ParallelMap claims doing map faster than the normal Map, and I checked the demo does as the document describing but, I try ...
Jerry's user avatar
  • 2,459
11 votes
2 answers
1k views

Most efficient way to obtain samples from high-dimensional multivariate distributions?

Is MultinormalDistribution[] efficient and easy to use for high dimensions? I have a variable $n$ representing the dimension of a Monte Carlo integration I do on a ...
Brian B's user avatar
  • 1,553
7 votes
2 answers
576 views

Fastest way to test if a numerical array has complex elements

I am looking for the fastest way to test whether an n-dimensional numerical (NumericQ) array (in the ArrayQ sense) is complex or ...
Szabolcs's user avatar
  • 234k
8 votes
1 answer
3k views

Why is parallel slower?

I always assumed that distributing a computation is faster, but it isn't necessarily true. When I do Sum[i,{i,10^4}] I retrieve an answer much faster then if I do <...
cspirou's user avatar
  • 231
13 votes
2 answers
423 views

Parallelization of distinct array write access from subkernels

I'm working on an implementation of a multivariate FFT, which is (or at least should be) highly parallelizable due to the row-column-algorithm. However, i can't figure out how to implement that. The ...
Ronny's user avatar
  • 1,141
14 votes
1 answer
579 views

Making Monte Carlo simulation with ParallelTable

I would like to to MonteCarlo simulations of various regressions - basically, doing OLS under various conditions to test approaches. On my macpro 2x 2.8 GHz quad core Xeon, 32 Gb RAM DDR2 @ 667 Mhz, ...
guylhem's user avatar
  • 241
2 votes
1 answer
724 views

How can I speed up image importing? [closed]

The following examples show how slow it is to load a simple GIF. Can anything be done to make it faster? System #1: Mathematica 8.0.1.0, HP notebook, Win7 64Bit, 2 x 2.4Ghz Intel Core i5, 2GB RAM, w/ ...
István Zachar's user avatar
1 vote
1 answer
1k views

ParallelTable 70 times slower on 16 cores than Table on single core

Consider these code(sorry it's messy), why the ParallelTable version is 70 times slower than the Table version? ...
xslittlegrass's user avatar
11 votes
1 answer
512 views

Why I only get 2X speedup when parallelized with 16 kernels

I'm trying to parallelize a function by ParallelTable, and it seems the speedup is not very good. I have 16 parallel kernels on my computer node: ...
xslittlegrass's user avatar
22 votes
1 answer
475 views

Two, maybe related, issues with ParallelTable

I will use a very simple example for demonstrating two issues I face with ParallelTable, one with respect to the speed and one with respect to the use of memory. These issues might be related. Let us ...
Fred Simons's user avatar
  • 10.2k

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