cfft2b cfft2f cfft2i rfft2b rfft2c rfft2f rfft2i

rfft2i() void rfft2i ( int  l, int  m, double  wsave[], int  lwsave, int *  info  ) Initialization of work data for rfft2f and rfft2b Purpose rfft2i initializes array wsave[] for use in its companion routines rfft2f and rfft2b. The prime factorization of n together with a tabulation of the trigonometric functions are computed and stored in array wsave[]. Note - The initialization of wsave[] is not necessary for the succeeding call of rfft2f or rfft2b for the same l and m values. If the value of l or m has been changed, wsave[] should be re-initialized by this routine. Parameters [in] l The number of elements to be transformed in the first dimension of the two-dimensional complex array r[][]. (l >= 1) The transform is most efficient when l is a product of small primes. [in] m The number of elements to be transformed in the second dimension of the two-dimensional complex array r[][]. (m >= 1) The transform is most efficient when m is a product of small primes. [out] wsave[] Array wsave[lwsave] Work data, containing the prime factors of n and also containing certain trigonometric values which will be used in routines rfft2f and rfft2b. [in] lwsave The length of the array wsave[]. (lwsave >= l + 3*m + ln(l)/ln(2) + 2*ln(m)/ln(2) + 12) [out] info = 0: Successful exit = -1: The argument l had an illegal value (l < 1) = -2: The argument m had an illegal value (m < 1) = -4: The argument lwsave had an illegal value (lwsave not big enough) Reference FFTPACK 5.1