Can I pass a subset of a matrix into another function in MKL?

Question

I am trying to optimize a lot of matrix calculations in MKL that requires me to allocate large blocks of memory using something like :

double* test_matrix = (double*)mkl_malloc(n * sizeof(double), 64).

Recently, I have been finding a lot of memory allocation errors that are popping up - which are hard to replicate and even harder to debug. I am worried that there is some internal header data that MKL puts into the heap that I am not accounting for using my current method.

Is there an "official" way of passing a subset of a MKL matrix into another function? Passing a copy would definitely increase my overhead too much. I am currently giving a reference of to the matrix subset like this:

double* a = (double*)mkl_malloc(4 * 4 * sizeof(double), 64);
double* b = (double*)mkl_malloc(4 * 4 * sizeof(double), 64);
double* c = (double*)mkl_malloc(2 * 2 * sizeof(double), 64);

... fill in values for a and b ...

cblas_dgemm(CblasRowMajor, CblasNoTrans, CblasNoTrans,
            2, 2, 2, 1, &a[2], 4, &b[2], 4, 0, c, 2);
cout << "Result is: " << c[0] << c[1] << c[2] << c[3] << endl; 

Answer 1

What you did is exactly the official way to reference a sub-matrix.

One of the most important reasons for BLAS functions to take leading dimensions of the matrices as input parameters is to enable easy referencing the sub-matrix without extra data copy.