/[lmdze]/trunk/Sources/misc/coefpoly.f
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trunk/dyn3d/coefpoly.f revision 82 by guez, Wed Mar 5 14:57:53 2014 UTC trunk/Sources/dyn3d/coefpoly.f revision 134 by guez, Wed Apr 29 15:47:56 2015 UTC
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1    module coefpoly_m
2    
 ! $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)  
3    IMPLICIT NONE    IMPLICIT NONE
4    
5    ! ...  Auteur :   P. Le Van  ...  contains
6    
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    ! Calcul des coefficients a0, a1, a2, a3 du polynome de degre 3 qui      DOUBLE PRECISION, intent(in):: xf1, xf2, xprim1, xprim2, xtild1, xtild2
28    ! satisfait aux 4 equations  suivantes :      DOUBLE PRECISION, intent(out):: a0, a1, a2, a3
29    
30    ! a0 + a1*xtild1 + a2*xtild1*xtild1 + a3*xtild1*xtild1*xtild1 = Xf1      ! Local:
31    ! a0 + a1*xtild2 + a2*xtild2*xtild2 + a3*xtild2*xtild2*xtild2 = Xf2      DOUBLE PRECISION xtil1car, xtil2car, derr, x1x2car
   ! a1  +     2.*a2*xtild1 +     3.*a3*xtild1*xtild1 = Xprim1  
   ! a1  +     2.*a2*xtild2 +     3.*a3*xtild2*xtild2 = Xprim2  
32    
33    ! On en revient a resoudre un systeme de 4 equat.a 4 inconnues a0,a1,a2,a3      !------------------------------------------------------------
34    
35    DOUBLE PRECISION xf1, xf2, xprim1, xprim2, xtild1, xtild2, xi      xtil1car = xtild1 * xtild1
36    DOUBLE PRECISION xfout, xprim      xtil2car = xtild2 * xtild2
   DOUBLE PRECISION a1, a2, a3, a0, xtil1car, xtil2car, derr, x1x2car  
37    
38    xtil1car = xtild1*xtild1      derr = 2. * (xf2-xf1)/(xtild1-xtild2)
   xtil2car = xtild2*xtild2  
39    
40    derr = 2.*(xf2-xf1)/(xtild1-xtild2)      x1x2car = (xtild1-xtild2) * (xtild1-xtild2)
41    
42    x1x2car = (xtild1-xtild2)*(xtild1-xtild2)      a3 = (derr+xprim1+xprim2)/x1x2car
43        a2 = (xprim1-xprim2+3. * a3 * (xtil2car-xtil1car))/(2. * (xtild1-xtild2))
44    
45    a3 = (derr+xprim1+xprim2)/x1x2car      a1 = xprim1 - 3. * a3 * xtil1car - 2. * a2 * xtild1
46    a2 = (xprim1-xprim2+3.*a3*(xtil2car-xtil1car))/(2.*(xtild1-xtild2))      a0 = xf1 - a3 * xtild1 * xtil1car - a2 * xtil1car - a1 * xtild1
47    
48    a1 = xprim1 - 3.*a3*xtil1car - 2.*a2*xtild1    END SUBROUTINE coefpoly
   a0 = xf1 - a3*xtild1*xtil1car - a2*xtil1car - a1*xtild1  
49    
50    RETURN  end module coefpoly_m
 END SUBROUTINE coefpoly  
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