dcost
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(*)
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
#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.