• NAME
• SYNOPSIS
• F95 INTERFACE
• C INTERFACE
• ARGUMENTS

NAME

vdcost - compute the discrete Fourier cosine transform of an even sequence. The VCOST transform is normalized, so a call of VCOST followed by a call of VCOST will return the original sequence.

SYNOPSIS

  SUBROUTINE VDCOST( M, N, X, XT, MDIMX, WSAVE)
  INTEGER M, N, MDIMX
  DOUBLE PRECISION X(MDIMX,*), XT(MDIMX,*), WSAVE(*)

  SUBROUTINE VDCOST_64( M, N, X, XT, MDIMX, WSAVE)
  INTEGER*8 M, N, MDIMX
  DOUBLE PRECISION X(MDIMX,*), XT(MDIMX,*), WSAVE(*)

F95 INTERFACE

  SUBROUTINE COST( [M], [N], X, XT, [MDIMX], WSAVE)
  INTEGER :: M, N, MDIMX
  REAL(8), DIMENSION(:) :: WSAVE
  REAL(8), DIMENSION(:,:) :: X, XT

  SUBROUTINE COST_64( [M], [N], X, XT, [MDIMX], WSAVE)
  INTEGER(8) :: M, N, MDIMX
  REAL(8), DIMENSION(:) :: WSAVE
  REAL(8), DIMENSION(:,:) :: X, XT

C INTERFACE

#include <sunperf.h>

void vdcost(int m, int n, double *x, double *xt, int mdimx, double *wsave);

void vdcost_64(long m, long n, double *x, double *xt, long mdimx, double *wsave);

ARGUMENTS

• M (input)
  The number of sequences to be transformed. M > = 0.

• N (input)
  Length of the sequence to be transformed. These subroutines are most efficient when N - 1 is a product of small primes. N > = 2.

• X (input/output)
  On entry, an array of length N containing the sequence to be transformed. For VCOST, a real two- dimensional array with dimensions of (MDIMX x (N+1)) whose rows contain the sequences to be transformed. On exit, the cosine transform of the input.

• XT (input)
  A real two-dimensional work array with dimensions of (MDIMX x (N-1)).

• MDIMX (input)
  Leading dimension of the arrays X and XT as specified in a dimension or type statement. MDIMX > = M.

• WSAVE (input)
  On entry, an array of dimension (2 * N + 15) or greater initialized by VDCOSTI.