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linear algebra - Is matrix multiplication automatically done in parallel in Mathematica 9?


In good old Mathematica versions (5.2, 6.0), matrix multiplication was automatically done in parallel. For example, on an 8-core machine, define two square real matrices:


m1 = Table[Random[Real], {256}, {256}];
m2 = Table[Random[Real], {256}, {256}];

The total CPU time used in all cores to compute a dot product is:



Tsingle = Timing[m1.m2][[1]]


0.010999 Second



The real time needed for the calculation is:


Tparallel = AbsoluteTiming[m1.m2][[1]]


0.001546 Second




For large matrices, the ratio is almost equal to the number of cores (8):


Tsingle / Tparallel


7.114489004



Repeating the same calculation in newer Mathematica versions (8.0, 9.0) gives Tsingle equal to Tparallel, which seems to indicate that new Mathematica versions dropped automatic parallelization of the Dot command. Is this true?
I would be thankful if anyone can advise how to regain this functionality, i.e. compute Dot products in parallel (automatically or manually).




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