NAME

blas_isortv - sorts a real vector X in increasing or decreasing order using quick sort algorithm and overwrite P with the permutation vector

SYNOPSIS

  SUBROUTINE BLAS_ISORTV( SORT, N, X, INCX, P, INCP)
  INTEGER SORT, N, INCX, INCP
  INTEGER X(*), P(*)

  SUBROUTINE BLAS_ISORTV_64( SORT, N, X, INCX, P, INCP)
  INTEGER*8 SORT, N, INCX, INCP
  INTEGER*8 X(*), P(*)

  SUBROUTINE SORTV( [SORT], [N], X, [INCX], P, [INCP])
  INTEGER :: SORT, N, INCX, INCP
  INTEGER, DIMENSION(:) :: X, P

  SUBROUTINE SORTV_64( [SORT], [N], X, [INCX], P, [INCP])
  INTEGER(8) :: SORT, N, INCX, INCP
  INTEGER(8), DIMENSION(:) :: X, P

#include <sunperf.h>

void blas_isortv(int sort, int n, int *x, int incx, int *p, int incp);

void blas_isortv_64(long sort, long n, long *x, long incx, long *p, long incp);

SORT (input)
SORT = 0, descending
SORT = 1, ascending

SORT = other value, error

SORT is default to 1 for F95 INTERFACE
N (input)
If N < = 1, the subroutine returns without trying to sort X.
X (input/output)
sorted
Minimum size (N-1)*|INCX|+1 is required
INCX (input)
INCX must not be zero. INCX could be negative. If INCX < 0, change the sorting direction defined by SORT. That is
If SORT = 0, let SORT = 1, INCX = |INCX|;

If SORT = 1, let SORT = 0, INCX = |INCX|.
P (output)
vector recording the details of the interchanges of the elements of X during sorting. That is X = P*X. In this implementation, P contains the index of sorted X.

INCP (input)
INCP must not be zero. INCP could be negative. If INCP < 0, store P(i) in reverse order. That is

If INCP > 0,

  if INCX  > 0,

    sorted X((i-1)*INCX+1)  = X(P((i-1)*INCP+1)),

  if INCX  < 0,

    sorted X((N-i)*|INCX|+1)  = X(P((i-1)*INCP+1));

If INCP < 0,

  if INCX  > 0,

    sorted X((i-1)*INCX+1)  = X(P((N-i)*|INCP|+1)),

  if INCX  < 0,

    sorted X((N-i)*|INCX|+1)

          = X(P((N-i)*|INCP|+1)).