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Дата изменения: Tue Aug 15 14:25:28 2000
Дата индексирования: Mon Oct 1 22:43:11 2012
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VEGAS menu

See Section 3.1 or [Lepage-1978,Press-1992] for explanation of the Vegas  algorithm. The work of Vegas  program is driven by Menu 6 of Fig..

The first position of this menu starts the process of Monte Carlo integration. It consists of Itmx runs with subsequent adaptation of the Monte Carlo weight function to the integrand. For each run Vegas  calls the integrand about Ncall times. The user may set the Itmx and Ncall parameters applying the next two items of the menu. The results of calculations are displayed on the screen and written to the protocol file.

If the required precision of calculation is not reached the user may call the Start integration menu function once more to increase the Monte Carlo statistic. But if the Clear statistic menu function is called, then the next Monte Carlo session will be started from the beginning. The Monte Carlo weight function is saved between runs anyway.

In the case of Fortran  n_comphep program the user can write weighted events generated by Vegas  into a file. The maximum and average values of event weights are displayed on the screen and written into the protocol file. The user must take into account that any new call of the Start integration menu function will rewrite this file.

In the case of C  version of the n_comphep program the user has a possibility to fill in some histograms during the Monte Carlo integration. In this case he needs to activate the Set Distribution function. This menu function opens a table of distributions which can be filled in by the user. The first column defines a phase space function which the user would like to scan. The set of available functions and the input format are defined in Section . The next two columns define a region of variation of the corresponding phase space function. There could be either a number or an algebraic expression containing the identifiers listed in the Model parameters menu.

The user can browse the distributions using the Display distributions menu function. This menu function asks the user to choose one distribution and a number of bins. After that the distribution appears. A call for Clear statistic menu function clears the stored distributions.