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* Contents: Native C interface to LAPACK utility function
* Author: Intel Corporation
* Created in February, 2010
*****************************************************************************/

#include "lapacke_utils.h"

/* Converts input triangular packed matrix from row-major(C) to
 * column-major(Fortran) layout or vice versa.
 */

void LAPACKE_stp_trans( int matrix_layout, char uplo, char diag,
                        lapack_int n, const float *in,
                        float *out )
{
    lapack_int i, j, st;
    lapack_logical colmaj, upper, unit;

    if( in == NULL || out == NULL ) return ;

    colmaj = ( matrix_layout == LAPACK_COL_MAJOR );
    upper  = LAPACKE_lsame( uplo, 'u' );
    unit   = LAPACKE_lsame( diag, 'u' );

    if( ( !colmaj && ( matrix_layout != LAPACK_ROW_MAJOR ) ) ||
        ( !upper  && !LAPACKE_lsame( uplo, 'l' ) ) ||
        ( !unit   && !LAPACKE_lsame( diag, 'n' ) ) ) {
        /* Just exit if any of input parameters are wrong */
        return;
    }
    if( unit ) {
        /* If unit, then don't touch diagonal, start from 1st column or row */
        st = 1;
    } else  {
        /* If non-unit, then check diagonal also, starting from [0,0] */
        st = 0;
    }

    /* Perform conversion:
     * Since col_major upper and row_major lower are equal,
     * and col_major lower and row_major upper are equals too -
     * using one code for equal cases. XOR( colmaj, upper )
     */
    if( !( colmaj || upper ) || ( colmaj && upper ) ) {
        for( j = st; j < n; j++ ) {
            for( i = 0; i < j+1-st; i++ ) {
                out[ j-i + (i*(2*n-i+1))/2 ] = in[ ((j+1)*j)/2 + i ];
            }
        }
    } else {
        for( j = 0; j < n-st; j++ ) {
            for( i = j+st; i < n; i++ ) {
                out[ j + ((i+1)*i)/2 ] = in[ (j*(2*n-j+1))/2 + i-j ];
            }
        }
    }
}
