share/hompack/fortran/strptp.f

   1       SUBROUTINE STRPTP(N,ICOUNT,IDEG,R ,X)
   2 C
   3 C COMPUTES INITIAL POINTS FOR PATHS.
   4 C
   5 C ON INPUT:
   6 C
   7 C N  IS THE NUMBER OF (COMPLEX) VARIABLES.
   8 C
   9 C ICOUNT  IS A COUNTER USED TO INCREMENT EACH
  10 C   VARIABLE AROUND THE UNIT CIRCLE SO THAT EVERY
  11 C   COMBINATION OF START VALUES IS CHOSEN.  ICOUNT  IS
  12 C   INITIALIZED IN  POLYP.
  13 C
  14 C IDEG(J)  IS THE DEGREE OF THE J-TH EQUATION.
  15 C
  16 C R(I,J)  IS A (COMPLEX) ARRAY GENERATED BY SUBROUTINE  INITP.
  17 C   R(1,J), AND R(2,J) ARE THE REAL AND IMAGINARY PARTS, RESPECTIVELY.
  18 C
  19 C ON OUTPUT:
  20 C
  21 C X(I,J)  IS INITIALIZED TO THE START VALUES FOR THE CURRENT PATH,
  22 C   WITH X(1,J) AND X(2,J) THE REAL AND IMAGINARY PARTS OF THE
  23 C   J-TH VARIABLE, RESPECTIVELY.
  24 C
  25 C SUBROUTINES:  ATAN, COS, MULP, SIN.
  26 C
  27 C DECLARATION OF INPUT AND OUTPUT:
  28       INTEGER N,ICOUNT,IDEG
  29       DOUBLE PRECISION R ,X
  30       DIMENSION ICOUNT(N),IDEG(N)
  31       DIMENSION R(2,N),X(2,N)
  32 C
  33 C DECLARATION OF VARIABLES:
  34       INTEGER J
  35       DOUBLE PRECISION TWOPI,ANGLE,XXXX
  36       DIMENSION XXXX(2)
  37 C
  38       DO 10 J=1,N
  39          IF(ICOUNT(J) .GE. IDEG(J) ) THEN
  40              ICOUNT(J)=1
  41            ELSE
  42              ICOUNT(J)=ICOUNT(J)+1
  43              GOTO 20
  44          END IF
  45   10  CONTINUE
  46   20  CONTINUE
  47       TWOPI = 8.0*ATAN(1.0)
  48       DO 30 J=1,N
  49           ANGLE = ( TWOPI/IDEG(J) )*ICOUNT(J)
  50           XXXX(1) = COS(ANGLE)
  51           XXXX(2) = SIN(ANGLE)
  52           CALL MULP(XXXX,R(1,J),X(1,J))
  53   30  CONTINUE
  54       RETURN
  55       END