Evaluating cells in parallel in Mathematica

Question

I have this many hundreds of cell long Mathematica file and I want to use parallel evaluation. I have a 2 processor x 4 core each machine with 16 Gb memory. My Mathematica license allows me to run at most 2 master kernels with 1 of the master could have 4 slave kernels (this is my interpretation after I played with it for a while).

I used to run my code in two master kernels in two different notebooks. To speed up things further, I tried to encapsulate a few cells with ParallelEvaluate[] and it seemed to work. Then I also have 4 copies of my code running unaware of each other through one of the master kernels, which is fine. (I am basically trying to run as many copies of my code/mathkernel in parallel as possible. I am not shooting for anything truly parallel yet).

Since my code is too long and complicated, I do not want to edit every cell again to make them evaluate in parallel. Is there anything magical I can put in the beginning of my notebook so every cell evaluated after that will be by default ParallelEvaluate[ ... cell contents.... ]?

Answer 1

As suggested by belisarius, $Pre=ParallelEvaluate does exactly what I want. One problem was when I do $Pre=Identity to turn it off so I can go back to my master kernel, mathematica still tries to evaluate that in slave kernels instead of master and fails. I ended up solving it as follows: SetSharedVariable[parallelcontrol]; parallelcontrol = ParallelEvaluate; $Pre := parallelcontrol; ... everything is evaluated in slaves here ... ; parallelcontrol = Identity; .... everything go back to be evaluated on master only ... Here is a sample run on my laptop which has 2 cores:

LaunchKernels[]

{KernelObject[1, "local"], KernelObject[2, "local"]}

$KernelID

0

ParallelEvaluate[$KernelID]

{1, 2}

SetSharedVariable[parcontrol]; $Pre := parcontrol; parcontrol = ParallelEvaluate

Null[ParallelEvaluate]

$KernelID

{1, 2}

parcontrol = Identity

{Identity, Identity}

$KernelID

0

parcontrol = ParallelEvaluate

ParallelEvaluate

$KernelID

{1, 2}