Sources/misc/coefpoly.f


! $Header: /home/cvsroot/LMDZ4/libf/dyn3d/coefpoly.F,v 1.1.1.1 2004/05/19
! 12:53:05 lmdzadmin Exp $

SUBROUTINE coefpoly(xf1, xf2, xprim1, xprim2, xtild1, xtild2, a0, a1, a2, a3)
  IMPLICIT NONE

  ! ...  Auteur :   P. Le Van  ...


  ! Calcul des coefficients a0, a1, a2, a3 du polynome de degre 3 qui
  ! satisfait aux 4 equations  suivantes :

  ! a0 + a1*xtild1 + a2*xtild1*xtild1 + a3*xtild1*xtild1*xtild1 = Xf1
  ! a0 + a1*xtild2 + a2*xtild2*xtild2 + a3*xtild2*xtild2*xtild2 = Xf2
  ! a1  +     2.*a2*xtild1 +     3.*a3*xtild1*xtild1 = Xprim1
  ! a1  +     2.*a2*xtild2 +     3.*a3*xtild2*xtild2 = Xprim2

  ! On en revient a resoudre un systeme de 4 equat.a 4 inconnues a0,a1,a2,a3

  DOUBLE PRECISION xf1, xf2, xprim1, xprim2, xtild1, xtild2, xi
  DOUBLE PRECISION xfout, xprim
  DOUBLE PRECISION a1, a2, a3, a0, xtil1car, xtil2car, derr, x1x2car

  xtil1car = xtild1*xtild1
  xtil2car = xtild2*xtild2

  derr = 2.*(xf2-xf1)/(xtild1-xtild2)

  x1x2car = (xtild1-xtild2)*(xtild1-xtild2)

  a3 = (derr+xprim1+xprim2)/x1x2car
  a2 = (xprim1-xprim2+3.*a3*(xtil2car-xtil1car))/(2.*(xtild1-xtild2))

  a1 = xprim1 - 3.*a3*xtil1car - 2.*a2*xtild1
  a0 = xf1 - a3*xtild1*xtil1car - a2*xtil1car - a1*xtild1

  RETURN
END SUBROUTINE coefpoly
1
2	! $Header: /home/cvsroot/LMDZ4/libf/dyn3d/coefpoly.F,v 1.1.1.1 2004/05/19
3	! 12:53:05 lmdzadmin Exp $
4
5	SUBROUTINE coefpoly(xf1, xf2, xprim1, xprim2, xtild1, xtild2, a0, a1, a2, a3)
6	IMPLICIT NONE
7
8	! ... Auteur : P. Le Van ...
9
10
11	! Calcul des coefficients a0, a1, a2, a3 du polynome de degre 3 qui
12	! satisfait aux 4 equations suivantes :
13
14	! a0 + a1xtild1 + a2xtild1xtild1 + a3xtild1xtild1xtild1 = Xf1
15	! a0 + a1xtild2 + a2xtild2xtild2 + a3xtild2xtild2xtild2 = Xf2
16	! a1 + 2.a2xtild1 + 3.a3xtild1*xtild1 = Xprim1
17	! a1 + 2.a2xtild2 + 3.a3xtild2*xtild2 = Xprim2
18
19	! On en revient a resoudre un systeme de 4 equat.a 4 inconnues a0,a1,a2,a3
20
21	DOUBLE PRECISION xf1, xf2, xprim1, xprim2, xtild1, xtild2, xi
22	DOUBLE PRECISION xfout, xprim
23	DOUBLE PRECISION a1, a2, a3, a0, xtil1car, xtil2car, derr, x1x2car
24
25	xtil1car = xtild1*xtild1
26	xtil2car = xtild2*xtild2
27
28	derr = 2.*(xf2-xf1)/(xtild1-xtild2)
29
30	x1x2car = (xtild1-xtild2)*(xtild1-xtild2)
31
32	a3 = (derr+xprim1+xprim2)/x1x2car
33	a2 = (xprim1-xprim2+3.a3(xtil2car-xtil1car))/(2.*(xtild1-xtild2))
34
35	a1 = xprim1 - 3.a3xtil1car - 2.a2xtild1
36	a0 = xf1 - a3xtild1xtil1car - a2xtil1car - a1xtild1
37
38	RETURN
39	END SUBROUTINE coefpoly