1 2C 3C * * * * * * * * * * * * * * * * * * * 4C * * 5C * SUBROUTINE VSSINI(N,C1,C2,WSAVE) * 6C * * 7C * * * * * * * * * * * * * * * * * * * 8C 9C 10C * * * * * * * * 11C * PURPOSE * 12C * * * * * * * * 13C 14C 15C A SUBROUTINE THAT COMPUTES INTERMEDIATE VALUES REQUIRED FOR THE 16C CALCULATION OF STAGGERED GRID COSINE AND SINE TRANSFORMS AND FOR 17C A REAL PERIODIC FAST FOURIER TRANSFORM. 18C 19C NOTE: SUBROUTINE VSCOSI OR VSSINI MUST BE CALLED BEFORE ANY OF 20C THE SUBROUTINES VSCOSF, VSCOSB, VSSINF, OR VSSINB ARE CALLED, BUT 21C IT NEED BE CALLED ONLY ONCE FOR ANY GIVEN VALUE OF N. 22C 23C 24C * * * * * * * * * * * * * * * 25C * PARAMETER DESCRIPTION * 26C * * * * * * * * * * * * * * * 27C 28C 29C INPUT PARAMETER 30C 31C N THE LENGTH OF THE STAGGERED GRID COSINE OR SINE TRANSFORM 32C TO BE COMPUTED. 33C 34C 35C OUTPUT PARAMETERS 36C 37C C1,C2 TWO REAL ONE-DIMENSIONAL ARRAYS OF LENGTH M THAT CONTAIN 38C INTERMEDIATE TRIGONOMETRIC VALUES USED IN THE STAGGERED 39C GRID TRANSFORMS. 40C 41C WSAVE A REAL ONE-DIMENSIONAL ARRAY OF LENGTH M+15 THAT CONTAINS 42C INTERMEDIATE VALUES CREATED BY THE SUBROUTINE VRFFTI FOR 43C USE IN THE COMPUTATION OF A REAL PERIODIC FAST FOURIER 44C TRANSFORM. 45C 46C NOTE: THE QUANTITIES IN THE ARRAYS C1, C2, AND WSAVE MUST NOT BE 47C DESTROYED BETWEEN SUCCESSIVE CALLS TO THE STAGGERED GRID 48C TRANSFORM ROUTINES. 49C 50C 51C 52C * * * * * * * * * * * * * * * * * * * * * 53C * * 54C * PROGRAM SPECIFICATIONS * 55C * * 56C * * * * * * * * * * * * * * * * * * * * * 57C 58C 59C 60C DIMENSION OF F(L,M,N), FT(L*M*N), C1(M), C2(M), C3(M), C4(M), 61C ARGUMENTS WSAVE(N+15) 62C 63C LATEST AUGUST 1, 1985 64C REVISION 65C 66C SUBPROGRAMS VSRFTI, VSCOSI, VSCSQI, VSRFTF, VSRFTB, VSCOSF, 67C REQUIRED VSCOSB, VSCOSQ, VSSINF, VSSINB, VSSINQ, PIMACH, 68C VRFFTPK (PACKAGE) 69C 70C SPECIAL NONE 71C CONDITIONS 72C 73C COMMON NONE 74C BLOCKS 75C 76C I/O NONE 77C 78C PRECISION SINGLE 79C 80C SPECIALIST ROLAND SWEET 81C 82C LANGUAGE FORTRAN 83C 84C HISTORY WRITTEN BY LINDA LINDGREN AND ROLAND SWEET AT THE 85C NATIONAL BUREAU OF STANDARDS (BOULDER). 86C 87C ALGORITHM SEE "FAST FOURIER TRANSFORMS ON A STAGGERED GRID" 88C BY ROLAND A. SWEET (TO APPEAR) 89C 90C PORTABILITY AMERICAN NATIONAL STANDARDS INSTITUTE FORTRAN 77. 91C THE ONLY MACHINE DEPENDENT CONSTANT IS LOCATED IN 92C THE FUNCTION PIMACH. 93C 94C REQUIRED COS,SIN 95C RESIDENT 96C ROUTINES 97C 98 99 100