Use a multiplication rather than a division to convert luminosities into...

Use a multiplication rather than a division to convert luminosities into fluxes. This should yield a small speedup.

CHANGELOG.md

@@ -9,6 +9,7 @@
 
 ### Optimised
 - A significant fraction of the total run time is spent computing integrals (e.g. fluxes in passbands). We can make the integration faster by rewriting the trapezoidal rule in terms of np.dot(). This allows to offload the computation to optimised libraries. The end result is that the integration is twice as fast, with a gain of ~10-15% on the total run time. (Médéric Boquien)
+- The conversion from luminosity to flux is now a bit faster. (Médéric Boquien)
 
 ## 0.9.0 (2016-04-04)
 ### Added

pcigale/sed/utils.py

@@ -65,9 +65,7 @@ def luminosity_to_flux(luminosity, dist):
 
     """
 
-    flux = luminosity / (4. * pi * dist * dist)
-
-    return flux
+    return luminosity * (1. / (4. * pi * dist * dist))
 
 
 def lambda_flambda_to_fnu(wavelength, flambda):