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Sorry I am relatively new to the parallel functionality mathematica.. Here is to code:

Try[] := Block[{temp},temp = Range[400]; Table[temp[[i]] = i^2 + 1, {i, 1, 400}];temp];

If you run it by its own, the result is satisfying. But when you try to evaluate it in parallel:


ParallelDo[Data[[i]] = Try[], {i, 1, 100}]; // Timing

The result is wrong:

What you get is

{0.171275, Null}

and if you try


It returns


instead of the correct value {2,5,10,......,160001}. Basically Data array is not processed at all in the ParallelDo. If you change it to ParallelTable, ParallelMap, its the same. Did I do any thing wrong in declaring Data=Range[100] or i have to make it shared?

Thanks for your help

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closed as off-topic by RunnyKine, rasher, Kuba, gpap, Sjoerd C. de Vries Apr 15 at 11:28

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I think you need SetSharedVariable[Data]. –  xzczd Apr 15 at 5:01
@xzczd thanks i will try! –  bboczeng Apr 15 at 5:10
@xzczd I think you are right! –  bboczeng Apr 15 at 5:24
possible duplicate of Definitions inside ParallelTable? –  xzczd Apr 15 at 6:27
If you use SetSharedVariable, it'll mostly negate the benefits of parallelization as it forces constant callbacks to the main kernel. Reformulate your problem in terms of side-effect-less functions such as Table. See here: mathematica.stackexchange.com/a/1771/12 and here: mathematica.stackexchange.com/a/2727/12 –  Szabolcs Apr 15 at 13:53

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