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******************************************************************************
* Contents: Native C interface to LAPACK utility function
* Author: Simon Märtens
*****************************************************************************/

#include "lapacke_utils.h"

/*****************************************************************************
  Check a trapezoidal matrix for NaN entries. The shape of the trapezoidal
  matrix is determined by the arguments `direct` and `uplo`. `Direct` chooses
  the diagonal which shall be considered and `uplo` tells us whether we use the
  upper or lower part of the matrix with respect to the chosen diagonal.

      Diagonals 'F' (front / forward) and 'B' (back / backward):

        A = ( F       )           A = ( F     B       )
            (    F    )               (    F     B    )
            ( B     F )               (       F     B )
            (    B    )
            (       B )

      direct = 'F', uplo = 'L':

        A = ( *       )           A = ( *             )
            ( *  *    )               ( *  *          )
            ( *  *  * )               ( *  *  *       )
            ( *  *  * )
            ( *  *  * )

      direct = 'F', uplo = 'U':

        A = ( *  *  * )           A = ( *  *  *  *  * )
            (    *  * )               (    *  *  *  * )
            (       * )               (       *  *  * )
            (         )
            (         )

      direct = 'B', uplo = 'L':

        A = (         )           A = ( *  *  *       )
            (         )               ( *  *  *  *    )
            ( *       )               ( *  *  *  *  * )
            ( *  *    )
            ( *  *  * )

      direct = 'B', uplo = 'U':

        A = ( *  *  * )           A = (       *  *  * )
            ( *  *  * )               (          *  * )
            ( *  *  * )               (             * )
            (    *  * )
            (       * )

*****************************************************************************/

lapack_logical LAPACKE_dtz_nancheck( int matrix_layout, char direct, char uplo,
                                     char diag, lapack_int m, lapack_int n,
                                     const double *a, lapack_int lda )
{
    lapack_logical colmaj, front, lower, unit;

    if( a == NULL ) return (lapack_logical) 0;

    colmaj = ( matrix_layout == LAPACK_COL_MAJOR );
    front  = LAPACKE_lsame( direct, 'f' );
    lower  = LAPACKE_lsame( uplo, 'l' );
    unit   = LAPACKE_lsame( diag, 'u' );

    if( ( !colmaj && ( matrix_layout != LAPACK_ROW_MAJOR ) ) ||
        ( !front  && !LAPACKE_lsame( direct, 'b' ) ) ||
        ( !lower  && !LAPACKE_lsame( uplo, 'u' ) ) ||
        ( !unit   && !LAPACKE_lsame( diag, 'n' ) ) ) {
        /* Just exit if any of input parameters are wrong */
        return (lapack_logical) 0;
    }

    /* Initial offsets and sizes of triangular and rectangular parts */
    lapack_int tri_offset = 0;
    lapack_int tri_n = MIN(m,n);
    lapack_int rect_offset = -1;
    lapack_int rect_m = ( m > n ) ? m - n : m;
    lapack_int rect_n = ( n > m ) ? n - m : n;

    /* Fix offsets depending on the shape of the matrix */
    if( front ) {
        if( lower && m > n ) {
            rect_offset = tri_n * ( !colmaj ? lda : 1 );
        } else if( !lower && n > m ) {
            rect_offset = tri_n * ( colmaj ? lda : 1 );
        }
    } else {
        if( m > n ) {
            tri_offset = rect_m * ( !colmaj ? lda : 1 );
            if( !lower ) {
                rect_offset = 0;
            }
        } else if( n > m ) {
            tri_offset = rect_n * ( colmaj ? lda : 1 );
            if( lower ) {
                rect_offset = 0;
            }
        }
    }

    /* Check rectangular part */
    if( rect_offset >= 0 ) {
        if( LAPACKE_dge_nancheck( matrix_layout, rect_m, rect_n,
                                  &a[rect_offset], lda ) ) {
            return (lapack_logical) 1;
        }
    }

    /* Check triangular part */
    return LAPACKE_dtr_nancheck( matrix_layout, uplo, diag, tri_n,
                                 &a[tri_offset], lda );
}
