source: LMDZ6/branches/Amaury_dev/libf/misc/lmdz_coefpoly.f90 @ 5221

Last change on this file since 5221 was 5119, checked in by abarral, 16 months ago

enforce PRIVATE by default in several modules, expose PUBLIC as needed
move eigen.f90 to obsolete/
(lint) aslong the way
  • Property copyright set to
    Name of program: LMDZ
    Creation date: 1984
    Version: LMDZ5
    License: CeCILL version 2
    Holder: Laboratoire de m\'et\'eorologie dynamique, CNRS, UMR 8539
    See the license file in the root directory
  • Property svn:eol-style set to native
  • Property svn:keywords set to Author Date Id Revision
File size: 1.5 KB
Line 
1module lmdz_coefpoly
2
3  IMPLICIT NONE; PRIVATE
4  PUBLIC coefpoly
5
6CONTAINS
7
8  SUBROUTINE coefpoly(xf1, xf2, xprim1, xprim2, xtild1, xtild2, a0, a1, a2, a3)
9
10    ! From LMDZ4/libf/dyn3d/coefpoly.F, version 1.1.1.1 2004/05/19 12:53:05
11
12    ! Author: P. Le Van
13
14    ! Calcul des coefficients a0, a1, a2, a3 du polynôme de degré 3 qui
15    ! satisfait aux 4 équations suivantes :
16
17    ! a0 + a1 * xtild1 + a2 * xtild1**2 + a3 * xtild1**3 = Xf1
18    ! a0 + a1 * xtild2 + a2 * xtild2**2 + a3 * xtild2**3 = Xf2
19    ! a1 + 2. * a2 * xtild1 + 3. * a3 * xtild1**2 = Xprim1
20    ! a1 + 2. * a2 * xtild2 + 3. * a3 * xtild2**2 = Xprim2
21
22    ! (passe par les points (Xf(it), xtild(it)) et (Xf(it + 1),
23    ! xtild(it + 1))
24
25    ! On en revient à resoudre un système de 4 équations à 4 inconnues
26    ! a0, a1, a2, a3.
27
28    USE lmdz_physical_constants, ONLY: k8
29
30    REAL(K8), INTENT(IN) :: xf1, xf2, xprim1, xprim2, xtild1, xtild2
31    REAL(K8), INTENT(OUT) :: a0, a1, a2, a3
32
33    ! Local:
34    REAL(K8) xtil1car, xtil2car, derr, x1x2car
35
36    !------------------------------------------------------------
37
38    xtil1car = xtild1 * xtild1
39    xtil2car = xtild2 * xtild2
40
41    derr = 2. * (xf2 - xf1) / (xtild1 - xtild2)
42
43    x1x2car = (xtild1 - xtild2) * (xtild1 - xtild2)
44
45    a3 = (derr + xprim1 + xprim2) / x1x2car
46    a2 = (xprim1 - xprim2 + 3. * a3 * (xtil2car - xtil1car)) / (2. * (xtild1 - xtild2))
47
48    a1 = xprim1 - 3. * a3 * xtil1car - 2. * a2 * xtild1
49    a0 = xf1 - a3 * xtild1 * xtil1car - a2 * xtil1car - a1 * xtild1
50
51  END SUBROUTINE coefpoly
52
53END MODULE lmdz_coefpoly
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