I'm having problems running cblas_dgemm on a matix matrix multiplication. I have the following matricies Code (Text): double * mass = new double[n]; double (* pos)[NDIM] = new double[n][NDIM]; double tempPos[NDIM]; double tempMass[nlocal]; double mass_avg; double pos_avg[NDIM]; The idea is to multiply the mass * tempMass and put it in mass_avg and multiple pos * tempPos and put it in pos_avg nlocal is less than n and it needs to multiple up to nlocal rows not n I'm using the following call for mass and it works as expected: Code (Text): cblas_dgemm(CblasRowMajor, CblasNoTrans, CblasNoTrans, 1, 1, nlocal, 1.0, mass, nlocal, tempMass, 1, 1.0, m_ave, 1); It's the position call that isn't working for me. I have the following for that one: Code (Text): cblas_dgemm(CblasRowMajor, CblasNoTrans, CblasNoTrans, nlocal, 1, NDIM, 1.0, pos, NDIM, tempPos, 1, 0.0, pos_ave, 1); I've been struggling with this for hours and can't figure out why the position call isn't working. I keep getting a segmentation fault. Any ideas about what's going on? Or what I'm doing wrong in this situation?