/[lmdze]/trunk/Sources/misc/coefpoly.f
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trunk/libf/dyn3d/coefpoly.f revision 71 by guez, Mon Jul 8 18:12:18 2013 UTC trunk/dyn3d/coefpoly.f revision 91 by guez, Wed Mar 26 17:18:58 2014 UTC
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 !  
 ! $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 )  )  
1    
2        a1     = Xprim1 -3.* a3 * xtil1car     -2.* a2 * xtild1  ! $Header: /home/cvsroot/LMDZ4/libf/dyn3d/coefpoly.F,v 1.1.1.1 2004/05/19
3        a0     =  Xf1 - a3 * xtild1* xtil1car -a2 * xtil1car - a1 *xtild1  ! 12:53:05 lmdzadmin Exp $
4    
5        RETURN  SUBROUTINE coefpoly(xf1, xf2, xprim1, xprim2, xtild1, xtild2, a0, a1, a2, a3)
6        END    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 + a1*xtild1 + a2*xtild1*xtild1 + a3*xtild1*xtild1*xtild1 = Xf1
15      ! a0 + a1*xtild2 + a2*xtild2*xtild2 + a3*xtild2*xtild2*xtild2 = Xf2
16      ! a1  +     2.*a2*xtild1 +     3.*a3*xtild1*xtild1 = Xprim1
17      ! a1  +     2.*a2*xtild2 +     3.*a3*xtild2*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
22      DOUBLE PRECISION a1, a2, a3, a0, xtil1car, xtil2car, derr, x1x2car
23    
24      xtil1car = xtild1*xtild1
25      xtil2car = xtild2*xtild2
26    
27      derr = 2.*(xf2-xf1)/(xtild1-xtild2)
28    
29      x1x2car = (xtild1-xtild2)*(xtild1-xtild2)
30    
31      a3 = (derr+xprim1+xprim2)/x1x2car
32      a2 = (xprim1-xprim2+3.*a3*(xtil2car-xtil1car))/(2.*(xtild1-xtild2))
33    
34      a1 = xprim1 - 3.*a3*xtil1car - 2.*a2*xtild1
35      a0 = xf1 - a3*xtild1*xtil1car - a2*xtil1car - a1*xtild1
36    
37    END SUBROUTINE coefpoly
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