Can anyone confirm the output of LAPACKE_dpstrf on matrix
a = [ 30, 11, 13,
11, 10, 13,
13, 13, 17]?
I got U = [5.47723,2.37346,2.00832
0,3.37145,2.44208
0,0,0.054153]
and U'*U =[30,13,11
13,17,13
11,13,10].
Therefore, the permutation matrix must be equal to (switching row/col 2 and 3)
P = [ 1 0 0
0 0 1
0 1 0]
However, the piv I got is [1,0,3], which makes no sense. So either I got the wrong piv or I made wrong interpretation of [1,0,3].
Here is the code
#include <stdlib.h>
#include <stdio.h>
#include "mkl_lapacke.h"
#include "mkl.h"
int main() {
double a[3*3] = {
30, 11, 13,
11, 10, 13,
13, 13, 17
};
int m=3;
lapack_int* piv = (lapack_int*)mkl_malloc(m*sizeof(lapack_int), 64);
long tmp = (long)piv;
int rank;
int info = LAPACKE_dpstrf(LAPACK_COL_MAJOR, 'U', m, a, m, piv, &rank, -1);
for(int i=1;i<=m;i++){
for(int j=1;j<=m;j++)
std::cout << a[(i-1)+(j-1)*m] << ", ";
std::cout << "\n";
}
for(int i=1;i<=m;i++)
std::cout << piv[i-1] << "\n";
mkl_free(piv);
}
