Esope source files

   1 : C JACOBF    SOURCE    CHAT      05/01/13    00:48:23     5004           
   2 : C
   3 :       SUBROUTINE JACOBF (POLY,PDER,POLYM1,PDERM1,POLYM2,PDERM2,
   4 :      $                   N,ALP,BET,X)
   5 : C--------------------------------------------------------------------
   6 : C
   7 : C     Computes the Jacobi polynomial (POLY) and its derivative (PDER)
   8 : C     of degree N at X.
   9 : C
  10 : C--------------------------------------------------------------------
  11 :       IMPLICIT INTEGER(I-N)
  12 :       IMPLICIT REAL*8 (A-H,O-Z)
  13 :       APB  = ALP+BET
  14 :       POLY = 1.D0
  15 :       PDER = 0.D0
  16 :       IF (N .EQ. 0) RETURN
  17 :       POLYL = POLY
  18 :       PDERL = PDER
  19 :       POLY  = (ALP-BET+(APB+2.D0)*X)/2.D0
  20 :       PDER  = (APB+2.D0)/2.D0
  21 :       IF (N .EQ. 1) RETURN
  22 :       DO 20 K=2,N
  23 :          DK =K
  24 :          A1 = 2.D0*DK*(DK+APB)*(2.D0*DK+APB-2.D0)
  25 :          A2 = (2.D0*DK+APB-1.D0)*(ALP**2-BET**2)
  26 :          B3 = (2.D0*DK+APB-2.D0)
  27 :          A3 = B3*(B3+1.D0)*(B3+2.D0)
  28 :          A4 = 2.D0*(DK+ALP-1.D0)*(DK+BET-1.D0)*(2.D0*DK+APB)
  29 :          POLYN  = ((A2+A3*X)*POLY-A4*POLYL)/A1
  30 :          PDERN  = ((A2+A3*X)*PDER-A4*PDERL+A3*POLY)/A1
  31 :          PSAVE  = POLYL
  32 :          PDSAVE = PDERL
  33 :          POLYL  = POLY
  34 :          POLY   = POLYN
  35 :          PDERL  = PDER
  36 :          PDER   = PDERN
  37 :  20   CONTINUE
  38 :       POLYM1 = POLYL
  39 :       PDERM1 = PDERL
  40 :       POLYM2 = PSAVE
  41 :       PDERM2 = PDSAVE
  42 :       RETURN
  43 :       END
  44 :  
  45 :