rfft2i

NAME

SYNOPSIS

 SUBROUTINE RFFT2I (L, M, WSAVE, LENSAV, IER)
 INTEGER    L, M, LENSAV, IER
 REAL       WSAVE(LENSAV)
 

DESCRIPTION

 FFTPACK 5.0 routine RFFT2I initializes real array WSAVE for use 
 in its companion routines RFFT2F and RFFT2B for computing the two-
 dimensional fast Fourier transform of real data.  Prime 
 factorizations of L and M, together with tabulations of the 
 trigonometric functions, are computed and stored in array WSAVE.
 RFFT2I must be called prior to the first call to RFFT2F or RFFT2B.
 Separate WSAVE arrays are required for different values of L or M.
 
 Input Arguments
 
 L       Integer number of elements to be transformed in the first 
         dimension.  The transform is most efficient when L is a 
         product of small primes.
 
 M       Integer number of elements to be transformed in the second 
         dimension.  The transform is most efficient when M is a 
         product of small primes.
 
 LENSAV  Integer number of elements in the WSAVE array.  LENSAV must
         be at least L + M + INT(LOG(REAL(L))) + INT(LOG(REAL(M))) +8.


 Output Arguments
 
 WSAVE   Real work array with dimension LENSAV, containing the
         prime factors of L and M, and also containing certain 
         trigonometric values which will be used in routines 
         RFFT2B or RFFT2F.


 IER     Integer error return
         =  0 successful exit
         =  2 input parameter LENSAV not big enough
         = 20 input error returned by lower level routine