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comparison +time/+expint/Magnus_mp.m @ 513:bc39bb984d88 feature/quantumTriangles

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Added arnoldi krylov subspace approximation
author Ylva Rydin <ylva.rydin@telia.com>
date Mon, 26 Jun 2017 20:15:54 +0200
parents 4ef2d2a493f1
children 8434063ed162
comparison
equal deleted inserted replaced
512:4ef2d2a493f1 513:bc39bb984d88
1 % Takes one time step of size k using the magnus midpoinr 1 % Takes one time step of size k using the magnus midpoinr
2 % starting from v_0 and where the function F(v,t) gives the 2 % starting from v_0 and where the function F(v,t) gives the
3 % time derivatives. 3 % time derivatives.
4 function v = Magnus_mp(v,D, t , k) 4 function v = Magnus_mp(v,D, t , k,matrixexp,tol)
5 5
6 if isa(D,'function_handle') 6 if isa(D,'function_handle')
7 % v = krylov(k*D(t +k/2*t),v); 7 Omega = D(t +k/2);
8 % v = expm(k*D(t +k/2))*v;
9 toler = 10^(-5);
10 expm_Arnoldi(-D,v,k,toler,100)
11 else 8 else
12 %v = krylov(k*D,v); 9 Omega = D;
13 % v = expm(k*D)*v;
14 end 10 end
15 11
12 switch matrixexp
13 case 'expm'
14 v = expm(k*Omega)*v;
15 case 'Arnoldi'
16 v = time.expint.expm_Arnoldi(-Omega,v,k,tol,100);
17 otherwise
18 error('No such matrix exponential evaluation')
19
16 end 20 end
21 end