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MathGroup Archive 2009

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Apply function breaks Parallelize?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg100090] Apply function breaks Parallelize?
  • From: elscimar at gmail.com
  • Date: Fri, 22 May 2009 23:41:25 -0400 (EDT)

Hello, all.

I'm trying to evaluate matrix multiplication in parallel, but I'm
running into a small snag.

I have a large vector of large matrices, and I want them multiplied.
However, I'm having difficulty getting it to parallelize, so I did a
little experiment.

This:

Parallelize[Dot[{{a,c},{b,d}},{{e,f},{g,h}},{{i,j},{k,l}},{{m,n},
{o,p}}]]

Evaluates without any problems.

However, if I try:

Parallelize[Dot@@{{{a,c},{b,d}},{{e,f},{g,h}},{{i,j},{k,l}},{{m,n},
{o,p}}}]

I get this error:
Parallelize::nopar1: Dot@@{{{a,c},{b,d}},{{e,f},{g,h}},{{i,j},{k,l}},
{{m,n},{o,p}}} cannot be parallelized; proceeding with sequential
evaluation. >>

Why would using the Apply[] function break Parallelize? If I type in
just the Dot@@{} bit, I get the exact same thing I'm putting into the
first one which works!


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