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Problem with alglib::smatrixtdevdr() http://forum.alglib.net/viewtopic.php?f=2&t=1014 |
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Author: | IlyaMischenko [ Tue Oct 01, 2013 11:40 am ] |
Post subject: | Problem with alglib::smatrixtdevdr() |
Hello, everybody! I`m a newcomer. I started using ALGLIB recently and faced a problem. I need an eigen-solver (symmetric tri-diagonal matrix). I tried three functions: alglib::smatrixtdevd() alglib::smatrixtdevdi() alglib::smatrixtdevdr() First two of them work almost normally, but the last one (for finding eigen pairs in a specified interval) gives 0 (or rarely 1) pair when it has to give a lot. What may be a problem? |
Author: | Sergey.Bochkanov [ Tue Oct 01, 2013 12:56 pm ] |
Post subject: | Re: Problem with alglib::smatrixtdevdr() |
Can you post your matrix here? I will investigate this issue as soon as I have data to investigate :) |
Author: | IlyaMischenko [ Tue Oct 01, 2013 2:52 pm ] | ||||
Post subject: | Re: Problem with alglib::smatrixtdevdr() | ||||
Thank you for the quick answer! Here is an example of required matrix: double S = 5. , k = 0.01 , hIk = 0.005 ; int N = (int) (2*S+1) ; double S2= S*(S+1) ; for ( int i=0; i<N; i++ ) { m1 = S-i ; m2 = 0-m1 ; D[i] = m1*m2/S2 - k*(m1*m1+m2*m2)/(2*S2) - hIk*k*m1/S ; E[i] = sqrt ( (S2-m1*(m1-1)) * (S2-m2*(m2+1)) ) / (2*S2) ; } S is spin. It`s ought to be interger or half-integer. I attach full source files too. One of them (smatrixtdevdi) works well, another one (smatrixtdevdr) gives wrong answer. I intended to send their outputs, but couldn`t attach more than three files.
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