|Program name||Package id||Status||Status date|
|Package ID||Orig. computer||Test computer|
|NEA-1895/01||Linux-based PC,PC Windows|
ENDSAM from a nuclear data library file of a chosen isotope in ENDF-6 format produces an arbitrary number of new files in ENDF-6 format which contain values of randomly sampled resonance parameters (in accordance with corresponding covariance matrices) in places of original values. The program works in the following steps:
reads resonance parameters and their covariance data from nuclear data libraries,
checks the consistency and mathematical correctness of the covariance data,
produces files containing randomly sampled resonance parameters.
Parameters are sampled according to the following distributions:
normal (resonance energy),
lognormal, multiplied with -1 (fission width, if it has negative mean value),
lognormal (all other parameters).
Random samples of resonance parameters are generated with transformation of correlation coefficients  and standard methods using Cholesky decomposition of correlation matrix and Box-Muller method  for generation of normally distributed random samples.
Due to the inconsistencies in nuclear data library, two issues may occur.
After transformation of correlation coefficients some correlations may not lie between -1 and 1. In this case original correlation matrix obtained from the library is used instead of the transformed one.
The transformed correlation matrix has the entries between -1 and 1, but is not positive definite. Then, in order to assure the existence of Cholesky decomposition, the correlation matrix is corrected by applying the Higham’s method  for calculating nearest positive definite correlation matrix.
The complete method is described in  and .
Memory used: up to 300MB.
Typical execution time ranges from a fraction of second up to few minutes per isotope on a PC.
If correlation matrix has many negative eigenvalues, then calculation of nearest positive definite correlation matrix may be time consuming. Otherwise, most of execution time is due to writing of resulting library files.
|Package ID||Status date||Status|
G.E.P. Box, M.E. Muller, A Note on the Generation of Random Normal Deviates, Ann. Math. Stat. 29, 610-611 (1958).
N.J. Higham, Computing the nearest correlation matrix -- a problem from finance, IMA J. Numer. Anal. 22, 329-343 (2002).
L. Plevnik, G. Žerovnik, A computer code for random sampling of resonance parameters and validation of the resonance parameters' covariance matrices of some major nuclear data libraries, IJS-DP-11939, Jožef Stefan Institute, Ljubljana, Slovenia, 2015.
L. Plevnik, G. Žerovnik, Computer code ENDSAM for random sampling and validation of the resonance parameters covariance matrices of some major nuclear data libraries, Ann. Nucl. Energy 94, 510-517 (2016)
G. Žerovnik, A. Trkov, D.L. Smith, R. Capote, Transformation of correlation coefficients between normal and lognormal distribution and implications for nuclear applications, Nucl. Instr. Meth. A 727, 33-39 (2013).
|Package ID||Computer language|
Keywords: ENDF-6, nuclear data, random sampling, resonance parameters.