share/colnew/fortran/vmonde.f

   1       SUBROUTINE VMONDE ( RHO, COEF, K )
   2 C
   3 C**********************************************************************
   4 C
   5 C   purpose
   6 C          solve vandermonde system v * x = e
   7 C          with  v(i,j) = rho(j)**(i-1)/(i-1)! .
   8 C
   9 C**********************************************************************
  10 C
  11       INTEGER K, I,IFAC,J,KM1,KMI
  12       DOUBLE PRECISION RHO(K), COEF(K)
  13 C
  14       IF ( K .EQ. 1 )                             RETURN
  15       KM1 = K - 1
  16       DO 10 I = 1, KM1
  17          KMI = K - I
  18          DO 10 J = 1, KMI
  19            COEF(J) = (COEF(J+1) - COEF(J)) / (RHO(J+I) - RHO(J))
  20   10  CONTINUE
  21 C
  22       IFAC = 1
  23       DO 40 I = 1, KM1
  24          KMI = K + 1 - I
  25          DO 30 J = 2, KMI
  26   30        COEF(J) = COEF(J) - RHO(J+I-1) * COEF(J-1)
  27          COEF(KMI) = DFLOAT(IFAC) * COEF(KMI)
  28          IFAC = IFAC * I
  29   40  CONTINUE
  30       COEF(1) = DFLOAT(IFAC) * COEF(1)
  31       RETURN
  32       END