I'm not sure what you mean. CBLAS includes this function to multiply two rectangular matrices: void cblas_dgemm( const CBLAS_LAYOUT Layout, const

I'm not sure what you mean. CBLAS includes this function to multiply two rectangular matrices: void cblas_dgemm( const CBLAS_LAYOUT Layout, const CBLAS_TRANSPOSE transa, const CBLAS_TRANSPOSE transb, const MKL_INT m, const MKL_INT n, const MKL_INT k, const double alpha, const double *a, const MKL_INT lda, const double *b, const MKL_INT ldb, const double beta, double *c, const MKL_INT ldc); gsl has a higher-level interface: int gsl_blas_dgemm(CBLAS_TRANSPOSE_t TransA, CBLAS_TRANSPOSE_t TransB, double alpha, const gsl_matrix * A, const gsl_matrix * B, double beta, gsl_matrix * C);