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Manuscript Title: A package of Linux scripts for the parallelization of Monte Carlo simulations
Authors: Andreu Badal, Josep Sempau
Program title: clonEasy
Catalogue identifier: ADYD_v1_0
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 175(2006)440
Programming language: Linux shell (bash) script, FORTRAN 77.
Computer: Any computer with a Unix style shell (bash), support for the Secure Shell protocol and a FORTRAN compiler.
Operating system: Linux (RedHat 8.0, SuSe 8.1, Debian Woody 3.1). Compilers, GNU FORTRAN g77 (Linux); g95 (Linux); Intel Fortran Compiler 7.1 (Linux).
Word size: 32 bits
Keywords: Monte Carlo, parallelization.
PACS: 02.70.Uu.
Classification: 6.5.

Nature of problem:
There are many situations where a Monte Carlo simulation involves a huge amount of CPU time. The parallelization of such calculations is a simple way of obtaining a relatively low statistical uncertainty using a reasonable amount of time.

Solution method:
The presented collection of Linux scripts and auxiliary FORTRAN programs implement Secure Shell-based communication between a "master" computer and a set of "clones". The aim of this communication is to execute a code that performs a Monte Carlo simulation on all the clones simultaneously. The code is unique, but each clone is fed with a different set of random seeds. Hence, clonEasy effectively permits the parallelization of the calculation.

clonEasy can only be used with programs that produce statistically independent results using the same code, but with a different sequence of random numbers. Users must choose the initialization values for the random number generator on each computer and combine the output from the different executions. A FORTRAN program to combine the final results is also provided.

Unusual features:
Any computer on the Internet with a Secure Shell client/server program installed can be used as a node of a virtual computer cluster for parallel calculations with the sequential source code. The simplicity of the parallelization scheme makes the use of this package a straightforward task, which does not require installing any additional libraries.

Additional comments:
The program, "seedsMLCG", referred to in the manuscript associated with this program, is held in the CPC Program Library as ADYE_v1_0.

Running time:
The execution time of each script largely depends on the number of computers that are used, the actions that are to be performed and, to a lesser extent, on the network connexion bandwidth.