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trunk/dyn3d/coefpoly.f revision 91 by guez, Wed Mar 26 17:18:58 2014 UTC trunk/Sources/misc/coefpoly.f revision 149 by guez, Thu Jun 18 12:23:44 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  ...    DOUBLE PRECISION a0, a1, a2, a3
6    
7    contains
8    
9      SUBROUTINE coefpoly(y1, y2, yp1, yp2, x1, x2)
10    
11        ! From LMDZ4/libf/dyn3d/coefpoly.F, version 1.1.1.1 2004/05/19 12:53:05
12    
13        ! Author: P. Le Van
14    
15    ! Calcul des coefficients a0, a1, a2, a3 du polynome de degre 3 qui      ! Calcul des coefficients a0, a1, a2, a3 du polynôme de degré 3
16    ! satisfait aux 4 equations  suivantes :      ! qui passe par les points (x1, Y1) et (x2, Y2) avec les
17        ! dérivées yp1 et yp2. Système linéaire de 4 équations à 4
18        ! inconnues :
19    
20    ! a0 + a1*xtild1 + a2*xtild1*xtild1 + a3*xtild1*xtild1*xtild1 = Xf1      ! a0 + a1 * x1 + a2 * x1**2 + a3 * x1**3 = Y1
21    ! a0 + a1*xtild2 + a2*xtild2*xtild2 + a3*xtild2*xtild2*xtild2 = Xf2      ! a0 + a1 * x2 + a2 * x2**2 + a3 * x2**3 = Y2
22    ! a1  +     2.*a2*xtild1 +     3.*a3*xtild1*xtild1 = Xprim1      ! a1 + 2 * a2 * x1 + 3 * a3 * x1**2 = Yp1
23    ! a1  +     2.*a2*xtild2 +     3.*a3*xtild2*xtild2 = Xprim2      ! a1 + 2 * a2 * x2 + 3 * a3 * x2**2 = Yp2
24    
25    ! On en revient a resoudre un systeme de 4 equat.a 4 inconnues a0,a1,a2,a3      DOUBLE PRECISION, intent(in):: y1, y2, yp1, yp2, x1, x2
26    
27    DOUBLE PRECISION xf1, xf2, xprim1, xprim2, xtild1, xtild2      ! Local:
28    DOUBLE PRECISION a1, a2, a3, a0, xtil1car, xtil2car, derr, x1x2car      DOUBLE PRECISION x1car, x2car
29    
30    xtil1car = xtild1*xtild1      !------------------------------------------------------------
   xtil2car = xtild2*xtild2  
31    
32    derr = 2.*(xf2-xf1)/(xtild1-xtild2)      x1car = x1 * x1
33        x2car = x2 * x2
34    
35    x1x2car = (xtild1-xtild2)*(xtild1-xtild2)      a3 = (2d0 * (y2-y1)/(x1-x2)+yp1+yp2)/((x1-x2) * (x1-x2))
36        a2 = (yp1-yp2+3d0 * a3 * (x2car-x1car))/(2d0 * (x1-x2))
37    
38    a3 = (derr+xprim1+xprim2)/x1x2car      a1 = yp1 - 3d0 * a3 * x1car - 2d0 * a2 * x1
39    a2 = (xprim1-xprim2+3.*a3*(xtil2car-xtil1car))/(2.*(xtild1-xtild2))      a0 = y1 - a3 * x1 * x1car - a2 * x1car - a1 * x1
40    
41    a1 = xprim1 - 3.*a3*xtil1car - 2.*a2*xtild1    END SUBROUTINE coefpoly
   a0 = xf1 - a3*xtild1*xtil1car - a2*xtil1car - a1*xtild1  
42    
43  END SUBROUTINE coefpoly  end module coefpoly_m
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