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I'm solving a much larger problem and have run into a bug when I try to use OpenMP to parallelize some loops. I've reproduced the problem with some simpler code below that mimics my own code. The problem is that when I run the program, it will randomly go into some sort of infinite loop/deadlock (CPU is 100%, but doesn't do anything). From what I can tell from my testing, one of the threads attempts to compute the matrix-matrix product but never finishes for some reason. I know that if you enable OpenMP, Eigen will parallelize matrix-matrix products using OpenMP . I'm also adding another parallel loop outside of this. However, this bug still occurs if I disable Eigen's parallelization by defining EIGEN_DONT_PARALLELIZE. I'm using gcc version 4.6.0 20101127 on MacOS 10.6.8 with Eigen 3.0.4. I can't figure out what could be going wrong... #include <iostream> #include <Eigen/Core> using namespace std; using namespace Eigen; MatrixXd Test(MatrixXd const& F, MatrixXd const& G) { MatrixXd H(F.rows(), G.cols()); H.noalias() = F*G; return H; } int main() { MatrixXd F = MatrixXd::Random(2,2); MatrixXd G = MatrixXd::Random(2,2); #pragma omp parallel for for (unsigned int i = 0; i < 10000; ++i) MatrixXd H = Test(F,G); cout << "Done!" << endl; }

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