!CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
!                                                                       
!   FFTPACK 5.0                                                         
!                                                                       
!   Authors:  Paul N. Swarztrauber and Richard A. Valent                
!                                                                       
!   $Id: mcstb1.f,v 1.2 2004/06/15 21:29:19 rodney Exp $                
!                                                                       
!CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
                                                                        
      SUBROUTINE MCSTB1(LOT,JUMP,N,INC,X,WSAVE,DSUM,WORK,IER) 
      REAL       X(INC,*)       ,WSAVE(*) 
      DOUBLE PRECISION           DSUM(*) 
      IER = 0 
      NM1 = N-1 
      NP1 = N+1 
      NS2 = N/2 
      LJ = (LOT-1)*JUMP+1 
      IF (N-2) 106,101,102 
  101 DO 111 M=1,LJ,JUMP 
         X1H = X(M,1)+X(M,2) 
         X(M,2) = X(M,1)-X(M,2) 
         X(M,1) = X1H 
  111 END DO 
      RETURN 
  102 IF (N .GT. 3) GO TO 103 
      DO 112 M=1,LJ,JUMP 
         X1P3 = X(M,1)+X(M,3) 
         X2 = X(M,2) 
         X(M,2) = X(M,1)-X(M,3) 
         X(M,1) = X1P3+X2 
         X(M,3) = X1P3-X2 
  112 END DO 
      RETURN 
  103 DO 118 M=1,LJ,JUMP 
      X(M,1) = X(M,1)+X(M,1) 
      X(M,N) = X(M,N)+X(M,N) 
  118 END DO 
      M1 = 0 
      DO 113 M=1,LJ,JUMP 
         M1 = M1+1 
         DSUM(M1) = X(M,1)-X(M,N) 
         X(M,1) = X(M,1)+X(M,N) 
  113 END DO 
      DO 104 K=2,NS2 
         M1 = 0 
         DO 114 M=1,LJ,JUMP 
         M1 = M1+1 
         KC = NP1-K 
         T1 = X(M,K)+X(M,KC) 
         T2 = X(M,K)-X(M,KC) 
         DSUM(M1) = DSUM(M1)+WSAVE(KC)*T2 
         T2 = WSAVE(K)*T2 
         X(M,K) = T1-T2 
         X(M,KC) = T1+T2 
  114    CONTINUE 
  104 END DO 
      MODN = MOD(N,2) 
      IF (MODN .EQ. 0) GO TO 124 
         DO 123 M=1,LJ,JUMP 
         X(M,NS2+1) = X(M,NS2+1)+X(M,NS2+1) 
  123    CONTINUE 
  124 CONTINUE 
      LENX = (LOT-1)*JUMP + INC*(NM1-1)  + 1 
      LNSV = NM1 + INT(LOG(REAL(NM1))) + 4 
      LNWK = LOT*NM1 
!                                                                       
      CALL RFFTMF(LOT,JUMP,NM1,INC,X,LENX,WSAVE(N+1),LNSV,WORK,         &
     &            LNWK,IER1)                                            
      IF (IER1 .NE. 0) THEN 
        IER = 20 
        CALL XERFFT ('MCSTB1',-5) 
        GO TO 106 
      ENDIF 
!                                                                       
      FNM1S2 = FLOAT(NM1)/2. 
      M1 = 0 
      DO 10 M=1,LJ,JUMP 
      M1 = M1+1 
      DSUM(M1) = .5*DSUM(M1) 
      X(M,1) = FNM1S2*X(M,1) 
   10 END DO 
      IF(MOD(NM1,2) .NE. 0) GO TO 30 
      DO 20 M=1,LJ,JUMP 
      X(M,NM1) = X(M,NM1)+X(M,NM1) 
   20 END DO 
   30 FNM1S4 = FLOAT(NM1)/4. 
      DO 105 I=3,N,2 
         M1 = 0 
         DO 115 M=1,LJ,JUMP 
            M1 = M1+1 
            XI = FNM1S4*X(M,I) 
            X(M,I) = FNM1S4*X(M,I-1) 
            X(M,I-1) = DSUM(M1) 
            DSUM(M1) = DSUM(M1)+XI 
  115 END DO 
  105 END DO 
      IF (MODN .NE. 0) RETURN 
      M1 = 0 
      DO 116 M=1,LJ,JUMP 
         M1 = M1+1 
         X(M,N) = DSUM(M1) 
  116 END DO 
  106 CONTINUE 
      RETURN 
      END