Mathematica Stack Exchange is a question and answer site for users of Mathematica. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I am having a problem which I guess is due to version difference. I have to generate a list of unitary matrices, which I can do easily. However I came to know about Parallelize command by which I wanted to speed the process. First the Hamiltonian (if anybody really wants to check)

X = 1/Sqrt[2] {{0, 1, 0}, {1, 0, 1}, {0, 1, 0}};
Y = I/Sqrt[2] {{0, -1, 0}, {1, 0, -1}, {0, 1, 0}};
Z = DiagonalMatrix[{1, 0, -1}];
Subscript[S, 1, x] = KroneckerProduct[X, IdentityMatrix[3], IdentityMatrix[3]];
Subscript[S, 2, x] = KroneckerProduct[IdentityMatrix[3], X, IdentityMatrix[3]];
Subscript[S, 3, x] = KroneckerProduct[IdentityMatrix[3], IdentityMatrix[3], X];
Subscript[S, 1, y] = KroneckerProduct[Y, IdentityMatrix[3], IdentityMatrix[3]];
Subscript[S, 2, y] = KroneckerProduct[IdentityMatrix[3], Y, IdentityMatrix[3]];
Subscript[S, 3, y] = KroneckerProduct[IdentityMatrix[3], IdentityMatrix[3], Y];
Subscript[S, 1, z] = KroneckerProduct[Z, IdentityMatrix[3], IdentityMatrix[3]];
Subscript[S, 2, z] =  KroneckerProduct[IdentityMatrix[3], Z, IdentityMatrix[3]];
Subscript[S, 3, z] = KroneckerProduct[IdentityMatrix[3], IdentityMatrix[3], Z];
H = Sum[Sum[(Subscript[S, i, x].Subscript[S, j, x] + 
      Subscript[S, i, y].Subscript[S, j, y] + 
      Subscript[S, i, z].Subscript[S, j, z]), {j, i + 1, 3}], {i, 1, 

Now, the table

unitary = ParallelTable[Chop[N[MatrixExp[I θ H]]], {θ, 0, 1, 1/100}]; // Timing

The problem is, it is not working in Mathematica 7 and gives the following errors:

MatrixExp::matsq: Argument 0 at position 1 is not a nonempty square matrix.

Mathematica 8 gives result without any trouble and error! I guess it is due to some version difference. Can someone give me a workaround method for both Mathematica 6 and 7? I can only use 6 for any lengthy calculation, and it seems to speed up the calculations a lot.

share|improve this question
up vote 3 down vote accepted

For version 7 I believe you need this before the ParallelTable call:


For version 6 I don't know, but presumably you will need to define H in each kernel manually.

share|improve this answer
can you tell me how to do that. this is the first time i am trying to use parallel process. i do not know how many kernels it will take (as some other guys use it for same purpose too). – RSG Jul 29 '12 at 11:34
@rsg as version 6 doesn't even have ParallelTable how are you going about this? – Mr.Wizard Jul 29 '12 at 11:37
true. there was a toolkit for 6 by which i hoped i could do some of the things. It seems it is not possible. i have to work in 7 instead. thanks for the help. – RSG Jul 29 '12 at 12:10
@rsg I'm not sure. I think you should not Accept this answer yet as someone may have a solution if they know to look at the question. – Mr.Wizard Jul 29 '12 at 12:13
@rsg just for completeness, the DistributeDefinitions-equivalent function in the PCT is called ExportEnvironment. However, I don't have version 6 or the PCT installed any more so unfortunately I can't test whether 6 can actually do this calculation correctly as stated. – Oleksandr R. Jul 31 '12 at 1:05

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.