Contents
dcost - compute the discrete Fourier cosine transform of an
even sequence. The COST transforms are unnormalized
inverses of themselves, so a call of COST followed by
another call of COST will multiply the input sequence by 2 *
(N-1).
SUBROUTINE DCOST(N, X, WSAVE)
INTEGER N
DOUBLE PRECISION X(*), WSAVE(*)
SUBROUTINE DCOST_64(N, X, WSAVE)
INTEGER*8 N
DOUBLE PRECISION X(*), WSAVE(*)
F95 INTERFACE
SUBROUTINE COST([N], X, WSAVE)
INTEGER :: N
REAL(8), DIMENSION(:) :: X, WSAVE
SUBROUTINE COST_64([N], X, WSAVE)
INTEGER(8) :: N
REAL(8), DIMENSION(:) :: X, WSAVE
C INTERFACE
#include <sunperf.h>
void dcost(int n, double *x, double *wsave);
void dcost_64(long n, double *x, double *wsave);
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. On exit, the cosine
transform of the input.
WSAVE (input)
On entry, an array with dimension of at least (3
* N + 15), initialized by DCOSTI.