Histogramming while VEGAS-integrating

[Matteo Cacciari]

The FORTRAN version of the VEGAS Monte Carlo integration routine
passes a weight to the integrand function, so that one can collect
it and the function value while integrating, and build histograms for
various differential distributions.

This option does not seem to be available when using gsl_monte_vegas_integrate.

By checking the code, the weight seems to be given by jacbin * bin_vol,
and it is not passed to the integrand. While jacbin can be accessed from
gsl_monte_vegas_state, bin_vol apparently cannot, so that the full weight
cannot be retrieved for a given event.

Am I correct? If so, does anybody have a workaround which does not involve 
patching the GSL routine? Could perhaps this feature be included in a 
future release?

Thanks,

			Matteo