share/hompack/fortran/gfunp.f

   1       SUBROUTINE GFUNP(N,IDEG,PDG,QDG,X,
   2      $ XDGM1,XDG,PXDGM1,PXDG,G,DG)
   3 C
   4 C GFUNP  EVALUATES THE START EQUATION "G".
   5 C
   6 C ON INPUT:
   7 C
   8 C N  IS THE NUMBER OF VARIABLES.
   9 C
  10 C IDEG(J)  IS THE DEGREE OF THE J-TH EQUATION.
  11 C
  12 C PDG(1,J), PDG(2,J)  ARE THE REAL AND IMAGINARY PARTS
  13 C   OF THE POWERS OF P USED TO DEFINE G.
  14 C
  15 C QDG(1,J), QDG(2,J)  ARE THE REAL AND IMAGINARY PARTS
  16 C   OF THE POWERS OF Q USED TO DEFINE G.
  17 C
  18 C X(1,J), X(2,J)  ARE THE REAL AND IMAGINARY PARTS OF THE
  19 C   J-TH INDEPENDENT VARIABLE.
  20 C
  21 C XDGM1,XDG,PXDGM1,PXDG ARE WORKSPACE ARRAYS.
  22 C
  23 C ON OUTPUT:
  24 C
  25 C N,IDEG,PDG,QDG, AND X  ARE UNCHANGED.
  26 C
  27 C G(1,J),G(2,J)  ARE THE REAL AND IMAGINARY PARTS OF THE
  28 C   J-TH START EQUATION.
  29 C
  30 C DG(1,J),DG(2,J)  ARE THE REAL AND IMAGINARY PARTS OF THE
  31 C   PARTIAL DERIVATIVES OF THE J-TH START EQUATION WITH RESPECT TO THE
  32 C   J-TH INDEPENDENT VARIABLE.
  33 C
  34 C SUBROUTINE:  MULP.
  35 C
  36 C DECLARATION OF INPUT AND OUTPUT:
  37       INTEGER N,IDEG
  38       DOUBLE PRECISION PDG,QDG,X,XDGM1,XDG,PXDGM1,PXDG,G,DG
  39       DIMENSION IDEG(N),PDG(2,N),QDG(2,N),X(2,N),
  40      $  XDGM1(2,N),XDG(2,N),PXDGM1(2,N),PXDG(2,N),
  41      $  G(2,N),DG(2,N)
  42 C
  43 C DECLARATION OF VARIABLES
  44       INTEGER I,J
  45 C
  46 C COMPUTE THE (IDEG-1)-TH AND IDEG-TH POWER OF X
  47       DO 5 J=1,N
  48         CALL POWP(IDEG(J)-1,X(1,J), XDGM1(1,J))
  49         CALL MULP(X(1,J),XDGM1(1,J), XDG(1,J))
  50   5   CONTINUE
  51 C
  52 C COMPUTE THE PRODUCT OF PDG AND XDGM1
  53       DO 10 J=1,N
  54           CALL MULP( PDG(1,J), XDGM1(1,J), PXDGM1(1,J) )
  55   10  CONTINUE
  56 C
  57 C COMPUTE THE PRODUCT OF PDG AND XDG
  58       DO 20 J=1,N
  59           CALL MULP( PDG(1,J), XDG(1,J), PXDG(1,J) )
  60   20  CONTINUE
  61       DO 30 J=1,N
  62       DO 30 I=1,2
  63           G(I,J)=PXDG(I,J) - QDG(I,J)
  64           DG(I,J)= IDEG(J)*PXDGM1(I,J)
  65   30  CONTINUE
  66       RETURN
  67       END