1 |
|
|
module coefpoly_m |
2 |
|
|
|
3 |
|
|
IMPLICIT NONE |
4 |
|
|
|
5 |
|
|
contains |
6 |
|
|
|
7 |
|
129 |
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 |
|
|
use nrtype, only: k8 |
28 |
|
|
|
29 |
|
|
REAL(K8), intent(in):: xf1, xf2, xprim1, xprim2, xtild1, xtild2 |
30 |
|
|
REAL(K8), intent(out):: a0, a1, a2, a3 |
31 |
|
|
|
32 |
|
|
! Local: |
33 |
|
|
REAL(K8) xtil1car, xtil2car, derr, x1x2car |
34 |
|
|
|
35 |
|
|
!------------------------------------------------------------ |
36 |
|
|
|
37 |
|
129 |
xtil1car = xtild1 * xtild1 |
38 |
|
129 |
xtil2car = xtild2 * xtild2 |
39 |
|
|
|
40 |
|
129 |
derr = 2. * (xf2-xf1)/(xtild1-xtild2) |
41 |
|
|
|
42 |
|
129 |
x1x2car = (xtild1-xtild2) * (xtild1-xtild2) |
43 |
|
|
|
44 |
|
129 |
a3 = (derr+xprim1+xprim2)/x1x2car |
45 |
|
129 |
a2 = (xprim1-xprim2+3. * a3 * (xtil2car-xtil1car))/(2. * (xtild1-xtild2)) |
46 |
|
|
|
47 |
|
129 |
a1 = xprim1 - 3. * a3 * xtil1car - 2. * a2 * xtild1 |
48 |
|
129 |
a0 = xf1 - a3 * xtild1 * xtil1car - a2 * xtil1car - a1 * xtild1 |
49 |
|
|
|
50 |
|
129 |
END SUBROUTINE coefpoly |
51 |
|
|
|
52 |
|
|
end module coefpoly_m |