sptruns.f

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C> @file
C>
C> Spectrally interpolate scalars to polar stereo
C> @author IREDELL @date 96-02-29
 
C> This subprogram spectrally truncates scalar fields on a global
C> cylindrical grid, returning the fields to specific pairs of polar
C> stereographic scalar fields. The wave-space can be either
C> triangular or rhomboidal. The grid-space can be either an
C> equally-spaced grid (with or without pole points) or a Gaussian
C> grid. The grid fields may have general indexing. The transforms
C> are all multiprocessed. Transform several fields at a time to
C> improve vectorization. Subprogram can be called from a
C> multiprocessing environment.
C>
C> PROGRAM HISTORY LOG:
C>   96-02-29  IREDELL
C>
C> @param IROMB    - INTEGER SPECTRAL DOMAIN SHAPE
C>                (0 FOR TRIANGULAR, 1 FOR RHOMBOIDAL)
C> @param MAXWV    - INTEGER SPECTRAL TRUNCATION
C> @param IDRTI    - INTEGER INPUT GRID IDENTIFIER
C>                (IDRTI=4 FOR GAUSSIAN GRID,
C>                 IDRTI=0 FOR EQUALLY-SPACED GRID INCLUDING POLES,
C>                 IDRTI=256 FOR EQUALLY-SPACED GRID EXCLUDING POLES)
C> @param IMAXI    - INTEGER EVEN NUMBER OF INPUT LONGITUDES.
C> @param JMAXI    - INTEGER NUMBER OF INPUT LATITUDES.
C> @param KMAX     - INTEGER NUMBER OF FIELDS TO TRANSFORM.
C> @param NPS      - INTEGER ODD ORDER OF THE POLAR STEREOGRAPHIC GRIDS
C> @param IPRIME   - INTEGER INPUT LONGITUDE INDEX FOR THE PRIME MERIDIAN.
C>                (DEFAULTS TO 1 IF IPRIME=0)
C>                (OUTPUT LONGITUDE INDEX FOR PRIME MERIDIAN ASSUMED 1.)
C> @param ISKIPI   - INTEGER SKIP NUMBER BETWEEN INPUT LONGITUDES
C>                (DEFAULTS TO 1 IF ISKIPI=0)
C> @param JSKIPI   - INTEGER SKIP NUMBER BETWEEN INPUT LATITUDES FROM SOUTH
C>                (DEFAULTS TO -IMAXI IF JSKIPI=0)
C> @param KSKIPI   - INTEGER SKIP NUMBER BETWEEN INPUT GRID FIELDS
C>                (DEFAULTS TO IMAXI*JMAXI IF KSKIPI=0)
C> @param KGSKIP   - INTEGER SKIP NUMBER BETWEEN GRID FIELDS
C>                (DEFAULTS TO NPS*NPS IF KGSKIP=0)
C> @param NISKIP   - INTEGER SKIP NUMBER BETWEEN GRID I-POINTS
C>                (DEFAULTS TO 1 IF NISKIP=0)
C> @param NJSKIP   - INTEGER SKIP NUMBER BETWEEN GRID J-POINTS
C>                (DEFAULTS TO NPS IF NJSKIP=0)
C> @param JCPU     - INTEGER NUMBER OF CPUS OVER WHICH TO MULTIPROCESS
C>                (DEFAULTS TO ENVIRONMENT NCPUS IF JCPU=0)
C> @param TRUE     - REAL LATITUDE AT WHICH PS GRID IS TRUE (USUALLY 60.)
C> @param XMESH    - REAL GRID LENGTH AT TRUE LATITUDE (M)
C> @param ORIENT   - REAL LONGITUDE AT BOTTOM OF NORTHERN PS GRID
C>                (SOUTHERN PS GRID WILL HAVE OPPOSITE ORIENTATION.)
C> @param GRIDI    - REAL (*) INPUT GRID FIELDS
C> @param GN       - REAL (*) NORTHERN POLAR STEREOGRAPHIC FIELDS
C> @param GS       - REAL (*) SOUTHERN POLAR STEREOGRAPHIC FIELDS
C>
C> SUBPROGRAMS CALLED:
C> - sptran()       Perform a scalar spherical transform
C> - sptgps()       Transform spectral scalar to polar stereo.
C> - ncpus()        Gets environment number of cpus
C>
C> Minimum grid dimensions for unaliased transforms to spectral:
C>   DIMENSION                   | LINEAR             | QUADRATIC
C>   -----------------------     | ---------          | -------------
C>   IMAX                        | 2*MAXWV+2          | 3*MAXWV/2*2+2
C>   JMAX (IDRT=4,IROMB=0)       | 1*MAXWV+1          | 3*MAXWV/2+1
C>   JMAX (IDRT=4,IROMB=1)       | 2*MAXWV+1          | 5*MAXWV/2+1
C>   JMAX (IDRT=0,IROMB=0)       | 2*MAXWV+3          | 3*MAXWV/2*2+3
C>   JMAX (IDRT=0,IROMB=1)       | 4*MAXWV+3          | 5*MAXWV/2*2+3
C>   JMAX (IDRT=256,IROMB=0)     | 2*MAXWV+1          | 3*MAXWV/2*2+1
C>   JMAX (IDRT=256,IROMB=1)     | 4*MAXWV+1          | 5*MAXWV/2*2+1
C>
      SUBROUTINE sptruns(IROMB,MAXWV,IDRTI,IMAXI,JMAXI,KMAX,NPS,
     &                   IPRIME,ISKIPI,JSKIPI,KSKIPI,KGSKIP,
     &                   NISKIP,NJSKIP,JCPU,TRUE,XMESH,ORIENT,
     &                   GRIDI,GN,GS)
      REAL GRIDI(*),GN(*),GS(*)
      REAL W((MAXWV+1)*((IROMB+1)*MAXWV+2)/2*2+1,KMAX)
C - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
C  TRANSFORM INPUT GRID TO WAVE
      jc=jcpu
      IF(jc.EQ.0) jc=ncpus()
      mx=(maxwv+1)*((iromb+1)*maxwv+2)/2
      mdim=2*mx+1
      jn=-jskipi
      IF(jn.EQ.0) jn=imaxi
      js=-jn
      inp=(jmaxi-1)*max(0,-jn)+1
      isp=(jmaxi-1)*max(0,-js)+1
      CALL sptran(iromb,maxwv,idrti,imaxi,jmaxi,kmax,
     &            iprime,iskipi,jn,js,mdim,kskipi,0,0,jc,
     &            w,gridi(inp),gridi(isp),-1)
C - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
C  TRANSFORM WAVE TO OUTPUT
      CALL sptgps(iromb,maxwv,kmax,nps,mdim,kgskip,niskip,njskip,
     &            true,xmesh,orient,w,gn,gs)
C - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
      END