--- trunk/Sources/dyn3d/invert_zoom_x.f	2015/07/07 17:49:23	154
+++ trunk/dyn3d/invert_zoom_x.f	2018/03/06 13:39:57	255
@@ -9,15 +9,15 @@
 
 contains
 
-  subroutine invert_zoom_x(xf, xtild, G, xlon, xprim, xuv)
+  subroutine invert_zoom_x(beta, xf, xtild, G, xlon, xprim, xuv)
 
     use coefpoly_m, only: coefpoly, a1, a2, a3
     USE dimens_m, ONLY: iim
-    use dynetat0_m, only: clon
+    use dynetat0_m, only: clon, grossismx
     use nr_util, only: pi_d, twopi_d
     use numer_rec_95, only: hunt, rtsafe
 
-    DOUBLE PRECISION, intent(in):: Xf(0:), xtild(0:), G(0:) ! (0:nmax)
+    DOUBLE PRECISION, intent(in):: beta, Xf(0:), xtild(0:), G(0:) ! (0:nmax)
 
     real, intent(out):: xlon(:), xprim(:) ! (iim)
 
@@ -32,10 +32,11 @@
     integer i, it
 
     DOUBLE PRECISION xvrai(iim), Gvrai(iim) 
-    ! intermediary variables because xlon and xprim are simple precision
+    ! intermediary variables because xlon and xprim are single precision
 
     !------------------------------------------------------------------
 
+    print *, "Call sequence information: invert_zoom_x"
     it = 0 ! initial guess
     h = twopi_d / iim
 
@@ -44,14 +45,27 @@
        ! - pi <= y < pi
        abs_y = abs(y)
 
-       call hunt(xf, abs_y, it, my_lbound = 0)
-       ! {0 <= it <= nmax - 1}
+       ! Distinguish boundaries in order to avoid roundoff error.
+       ! funcd should be exactly equal to 0 at xtild(it) or xtild(it +
+       ! 1) and could be very small with the wrong sign so rtsafe
+       ! would fail.
+       if (abs_y == 0d0) then
+          xvrai(i) = 0d0
+          gvrai(i) = grossismx
+       else if (abs_y == pi_d) then
+          xvrai(i) = pi_d
+          gvrai(i) = 2d0 * beta - grossismx
+       else
+          call hunt(xf, abs_y, it, my_lbound = 0)
+          ! {0 <= it <= nmax - 1}
+
+          ! Calcul de xvrai(i) et Gvrai(i)
+          CALL coefpoly(Xf(it), Xf(it + 1), G(it), G(it + 1), xtild(it), &
+               xtild(it + 1))
+          xvrai(i) = rtsafe(funcd, xtild(it), xtild(it + 1), xacc = 1d-6)
+          Gvrai(i) = a1 + xvrai(i) * (2d0 * a2 + xvrai(i) * 3d0 * a3)
+       end if
 
-       ! Calcul de xvrai(i) et Gvrai(i)
-       CALL coefpoly(Xf(it), Xf(it + 1), G(it), G(it + 1), xtild(it), &
-            xtild(it + 1))
-       xvrai(i) = rtsafe(funcd, xtild(it), xtild(it + 1), xacc = 1d-6)
-       Gvrai(i) = a1 + xvrai(i) * (2d0 * a2 + xvrai(i) * 3d0 * a3)
        if (y < 0d0) xvrai(i) = - xvrai(i)
     end DO