1 |
! |
module coefpoly_m |
|
! $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 |
|
|
c |
|
|
c ... Auteur : P. Le Van ... |
|
|
c |
|
|
c |
|
|
c Calcul des coefficients a0, a1, a2, a3 du polynome de degre 3 qui |
|
|
c satisfait aux 4 equations suivantes : |
|
|
|
|
|
c a0 + a1*xtild1 + a2*xtild1*xtild1 + a3*xtild1*xtild1*xtild1 = Xf1 |
|
|
c a0 + a1*xtild2 + a2*xtild2*xtild2 + a3*xtild2*xtild2*xtild2 = Xf2 |
|
|
c a1 + 2.*a2*xtild1 + 3.*a3*xtild1*xtild1 = Xprim1 |
|
|
c a1 + 2.*a2*xtild2 + 3.*a3*xtild2*xtild2 = Xprim2 |
|
|
|
|
|
c 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 ) ) |
|
2 |
|
|
3 |
a1 = Xprim1 -3.* a3 * xtil1car -2.* a2 * xtild1 |
IMPLICIT NONE |
|
a0 = Xf1 - a3 * xtild1* xtil1car -a2 * xtil1car - a1 *xtild1 |
|
4 |
|
|
5 |
RETURN |
contains |
6 |
END |
|
7 |
|
SUBROUTINE coefpoly(xf1, xf2, xprim1, xprim2, xtild1, xtild2, a0, a1, a2, a3) |
8 |
|
|
9 |
|
! From LMDZ4/libf/dyn3d/coefpoly.F, version 1.1.1.1 2004/05/19 12:53:05 |
10 |
|
|
11 |
|
! Author: P. Le Van |
12 |
|
|
13 |
|
! Calcul des coefficients a0, a1, a2, a3 du polynôme de degré 3 qui |
14 |
|
! satisfait aux 4 équations suivantes : |
15 |
|
|
16 |
|
! a0 + a1 * xtild1 + a2 * xtild1**2 + a3 * xtild1**3 = Xf1 |
17 |
|
! a0 + a1 * xtild2 + a2 * xtild2**2 + a3 * xtild2**3 = Xf2 |
18 |
|
! a1 + 2. * a2 * xtild1 + 3. * a3 * xtild1**2 = Xprim1 |
19 |
|
! a1 + 2. * a2 * xtild2 + 3. * a3 * xtild2**2 = Xprim2 |
20 |
|
|
21 |
|
! (passe par les points (Xf(it), xtild(it)) et (Xf(it + 1), |
22 |
|
! xtild(it + 1)) |
23 |
|
|
24 |
|
! On en revient à resoudre un système de 4 équations à 4 inconnues |
25 |
|
! a0, a1, a2, a3. |
26 |
|
|
27 |
|
DOUBLE PRECISION, intent(in):: xf1, xf2, xprim1, xprim2, xtild1, xtild2 |
28 |
|
DOUBLE PRECISION, intent(out):: a0, a1, a2, a3 |
29 |
|
|
30 |
|
! Local: |
31 |
|
DOUBLE PRECISION xtil1car, xtil2car, derr, x1x2car |
32 |
|
|
33 |
|
!------------------------------------------------------------ |
34 |
|
|
35 |
|
xtil1car = xtild1 * xtild1 |
36 |
|
xtil2car = xtild2 * xtild2 |
37 |
|
|
38 |
|
derr = 2. * (xf2-xf1)/(xtild1-xtild2) |
39 |
|
|
40 |
|
x1x2car = (xtild1-xtild2) * (xtild1-xtild2) |
41 |
|
|
42 |
|
a3 = (derr+xprim1+xprim2)/x1x2car |
43 |
|
a2 = (xprim1-xprim2+3. * a3 * (xtil2car-xtil1car))/(2. * (xtild1-xtild2)) |
44 |
|
|
45 |
|
a1 = xprim1 - 3. * a3 * xtil1car - 2. * a2 * xtild1 |
46 |
|
a0 = xf1 - a3 * xtild1 * xtil1car - a2 * xtil1car - a1 * xtild1 |
47 |
|
|
48 |
|
END SUBROUTINE coefpoly |
49 |
|
|
50 |
|
end module coefpoly_m |