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[Help-gsl] gsl vs ARPACK++

From: Rafal Topolnicki
Subject: [Help-gsl] gsl vs ARPACK++
Date: Tue, 24 Aug 2010 23:08:52 +0200
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv: Gecko/20100720 Lanikai/3.1.1


I need to compute 10% of smallest eigenvalues of huge (3432x3432, 12870x12870, 184756x184756) real symmetric sparse matrix (over 99,8% of elements =0). At first I tried to do it using GSL and in first case it take ~160s to capure all eigenvalues. Because matrix is extremely sparse I thought that it will be faster if I use ARPACK++ instead of gsl. I use function

ARluSymStdEig<double> dprob(ilosc_wartosci, matrix, "SM");

where ilosc_wartosci is number of eigenvalues I want to compute.
It works, but I takes ~129s to compute 10% of all eigenvalues. I thought I would be much faster.
My question is, if gsl is so good, ARPACK++ so bad or am I doing sth wrong.

BTW, ARPACK++ use sparse matrix in CSC format. Is it possible to write matrix with columns consisting only zeros using this code?


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