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module coefpoly_m |
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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 $ |
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SUBROUTINE coefpoly ( Xf1, Xf2, Xprim1, Xprim2, xtild1,xtild2 , |
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, a0,a1,a2,a3 ) |
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IMPLICIT NONE |
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c |
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c ... Auteur : P. Le Van ... |
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c |
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c |
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c Calcul des coefficients a0, a1, a2, a3 du polynome de degre 3 qui |
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c satisfait aux 4 equations suivantes : |
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c a0 + a1*xtild1 + a2*xtild1*xtild1 + a3*xtild1*xtild1*xtild1 = Xf1 |
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c a0 + a1*xtild2 + a2*xtild2*xtild2 + a3*xtild2*xtild2*xtild2 = Xf2 |
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c a1 + 2.*a2*xtild1 + 3.*a3*xtild1*xtild1 = Xprim1 |
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c a1 + 2.*a2*xtild2 + 3.*a3*xtild2*xtild2 = Xprim2 |
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c On en revient a resoudre un systeme de 4 equat.a 4 inconnues a0,a1,a2,a3 |
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DOUBLE PRECISION Xf1, Xf2,Xprim1,Xprim2, xtild1,xtild2, xi |
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DOUBLE PRECISION Xfout, Xprim |
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DOUBLE PRECISION a1,a2,a3,a0, xtil1car, xtil2car,derr,x1x2car |
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xtil1car = xtild1 * xtild1 |
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xtil2car = xtild2 * xtild2 |
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derr= 2. *(Xf2-Xf1)/( xtild1-xtild2) |
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x1x2car = ( xtild1-xtild2)*(xtild1-xtild2) |
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a3 = (derr + Xprim1+Xprim2 )/x1x2car |
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a2 = ( Xprim1 - Xprim2 + 3.* a3 * ( xtil2car-xtil1car ) ) / |
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/ ( 2.* ( xtild1 - xtild2 ) ) |
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a1 = Xprim1 -3.* a3 * xtil1car -2.* a2 * xtild1 |
IMPLICIT NONE |
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a0 = Xf1 - a3 * xtild1* xtil1car -a2 * xtil1car - a1 *xtild1 |
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RETURN |
DOUBLE PRECISION a0, a1, a2, a3 |
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END |
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contains |
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SUBROUTINE coefpoly(y1, y2, yp1, yp2, x1, x2) |
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! From LMDZ4/libf/dyn3d/coefpoly.F, version 1.1.1.1 2004/05/19 12:53:05 |
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! Author: P. Le Van |
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! Calcul des coefficients a0, a1, a2, a3 du polynôme de degré 3 |
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! qui passe par les points (x1, Y1) et (x2, Y2) avec les |
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! dérivées yp1 et yp2. Système linéaire de 4 équations à 4 |
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! inconnues : |
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! a0 + a1 * x1 + a2 * x1**2 + a3 * x1**3 = Y1 |
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! a0 + a1 * x2 + a2 * x2**2 + a3 * x2**3 = Y2 |
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! a1 + 2 * a2 * x1 + 3 * a3 * x1**2 = Yp1 |
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! a1 + 2 * a2 * x2 + 3 * a3 * x2**2 = Yp2 |
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DOUBLE PRECISION, intent(in):: y1, y2, yp1, yp2, x1, x2 |
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! Local: |
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DOUBLE PRECISION x1car, x2car |
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!------------------------------------------------------------ |
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x1car = x1 * x1 |
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x2car = x2 * x2 |
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a3 = (2d0 * (y2-y1)/(x1-x2)+yp1+yp2)/((x1-x2) * (x1-x2)) |
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a2 = (yp1-yp2+3d0 * a3 * (x2car-x1car))/(2d0 * (x1-x2)) |
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a1 = yp1 - 3d0 * a3 * x1car - 2d0 * a2 * x1 |
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a0 = y1 - a3 * x1 * x1car - a2 * x1car - a1 * x1 |
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END SUBROUTINE coefpoly |
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end module coefpoly_m |
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