Thanks for pointing this out. Once more I realize that loops are to be avoided. Your suggestions make the creation of the generator matrices (lambdas) notably faster. However, once they are created, the problem is the repeated use of the MatrixExponential command and also the many matrix-matrix multiplications (which seem to eat up roughly the same amount of CPU time as the matrix exponentials...). Of course, I understand that Matlab is more optimized on the numerical side, but I guess one could squeeze out a bit more performance if one tells Maple how to do it, right? So does anyone have a suggestion for this?