module lmdz_coefpoly IMPLICIT NONE contains SUBROUTINE coefpoly(xf1, xf2, xprim1, xprim2, xtild1, xtild2, a0, a1, a2, a3) ! From LMDZ4/libf/dyn3d/coefpoly.F, version 1.1.1.1 2004/05/19 12:53:05 ! Author: P. Le Van ! Calcul des coefficients a0, a1, a2, a3 du polynôme de degré 3 qui ! satisfait aux 4 équations suivantes : ! a0 + a1 * xtild1 + a2 * xtild1**2 + a3 * xtild1**3 = Xf1 ! a0 + a1 * xtild2 + a2 * xtild2**2 + a3 * xtild2**3 = Xf2 ! a1 + 2. * a2 * xtild1 + 3. * a3 * xtild1**2 = Xprim1 ! a1 + 2. * a2 * xtild2 + 3. * a3 * xtild2**2 = Xprim2 ! (passe par les points (Xf(it), xtild(it)) et (Xf(it + 1), ! xtild(it + 1)) ! On en revient à resoudre un système de 4 équations à 4 inconnues ! a0, a1, a2, a3. use nrtype, only: k8 REAL(K8), intent(in) :: xf1, xf2, xprim1, xprim2, xtild1, xtild2 REAL(K8), intent(out) :: a0, a1, a2, a3 ! Local: REAL(K8) 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)) a1 = xprim1 - 3. * a3 * xtil1car - 2. * a2 * xtild1 a0 = xf1 - a3 * xtild1 * xtil1car - a2 * xtil1car - a1 * xtild1 END SUBROUTINE coefpoly end module lmdz_coefpoly