dcosqf

NAME

dcosqf - compute the Fourier coefficients in a cosine series representation with only odd wave numbers. The COSQ operations are unnormalized inverses of themselves, so a call to COSQF followed by a call to COSQB will multiply the input sequence by 4 * N.

SYNOPSIS

  SUBROUTINE DCOSQF( N, X, WSAVE)
  INTEGER N
  DOUBLE PRECISION X(*), WSAVE(*)
 
  SUBROUTINE DCOSQF_64( N, X, WSAVE)
  INTEGER*8 N
  DOUBLE PRECISION X(*), WSAVE(*)

F95 INTERFACE

  SUBROUTINE COSQF( [N], X, WSAVE)
  INTEGER :: N
  REAL(8), DIMENSION(:) :: X, WSAVE
 
  SUBROUTINE COSQF_64( [N], X, WSAVE)
  INTEGER(8) :: N
  REAL(8), DIMENSION(:) :: X, WSAVE

C INTERFACE

#include <sunperf.h>

void dcosqf(int n, double *x, double *wsave);

void dcosqf_64(long n, double *x, double *wsave);

ARGUMENTS

* N (input): Length of the sequence to be transformed. These subroutines are most efficient when N is a product of small primes. N >= 0.
* X (input/output): On entry, an array of length N containing the sequence to be transformed. On exit, the quarter-wave cosine transform of the input.
* WSAVE (input): On entry, an array with dimension of at least (3 * N + 15) that has been initialized by DCOSQI.