@mikrom: please take a look at the following link.You would see the difference in the use of GEMM (via Math Kernel Library wrapped up by Intel) and xGEMM. Put briefly, the shortest form could be "GEMM(a,b,c)" as opposed to "call dgemm(transa, transb, m, n, k, alpha, a, lda, b, ldb, beta, c, ldc).