Check to ensure that the value passed to exp doesn't cause an underfl…

…ow exception

src/ejecta/ejecta_ray_func.f90

@@ -33,13 +33,18 @@ function ejecta_ray_func(theta,thetar,r,n,w) result(ans)
     real(DP) :: ans
     real(DP),intent(in) :: theta,thetar,r,w
     integer(I4B),intent(in) :: n
-    real(DP) :: thetap,thetapp,a,b,c,dtheta
+    real(DP) :: thetap,thetapp,a,b,c,dtheta,logval
 
     c = w / r
     b = thetar 
     dtheta = min(2*pi - abs(theta - b),abs(theta - b))
-    a = sqrt(2 * pi) / (n * c * erf(pi / (2 *sqrt(2._DP) * c))) !this is the intensity function
-    ans = a * exp(-dtheta**2 / (2 * c**2))
+    logval = -dtheta**2 / (2 * c**2)
+    if (logval < LOGVSMALL) then
+        ans = 0.0_DP
+    else
+        a = sqrt(2 * pi) / (n * c * erf(pi / (2 *sqrt(2._DP) * c))) !this is the intensity function
+        ans = a * exp(logval)
+    end if
 
-!return
+    return
 end function ejecta_ray_func