Mercurial > repos > public > sbplib
view +sbp/+implementations/d4_compatible_2.m @ 267:f7ac3cd6eeaa operator_remake
Sparsified all implementation files, removed all matlab warnings, fixed small bugs on minimum grid points.
author | Martin Almquist <martin.almquist@it.uu.se> |
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date | Fri, 09 Sep 2016 14:53:41 +0200 |
parents | bfa130b7abf6 |
children |
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function [H, HI, D1, D4, e_1, e_m, M4, Q, S2_1, S2_m,... S3_1, S3_m, S_1, S_m] = d4_compatible_2(m,h) %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%% 4:de ordn. SBP Finita differens %%% %%% operatorer framtagna av Ken Mattsson %%% %%% %%% %%% 6 randpunkter, diagonal norm %%% %%% %%% %%% Datum: 2013-11-11 %%% %%% %%% %%% %%% %%% H (Normen) %%% %%% D1 (approx f?rsta derivatan) %%% %%% D2 (approx andra derivatan) %%% %%% D3 (approx tredje derivatan) %%% %%% D2 (approx fj?rde derivatan) %%% %%% %%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % M?ste ange antal punkter (m) och stegl?ngd (h) % Notera att dessa opetratorer ?r framtagna f?r att anv?ndas n?r % vi har 3de och 4de derivator i v?r PDE % I annat fall anv?nd de "traditionella" som har noggrannare % randsplutningar f?r D1 och D2 % Vi b?rjar med normen. Notera att alla SBP operatorer delar samma norm, % vilket ?r n?dv?ndigt f?r stabilitet BP = 4; if(m<2*BP) error(['Operator requires at least ' num2str(2*BP) ' grid points']); end H=speye(m,m);H(1,1)=1/2;H(m,m)=1/2; H=H*h; HI=inv(H); % First derivative SBP operator, 1st order accurate at first 6 boundary points q1=1/2; % Q=q1*(diag(ones(m-1,1),1)-diag(ones(m-1,1),-1)); stencil = [-q1,0,q1]; d = (length(stencil)-1)/2; diags = -d:d; Q = stripeMatrix(stencil, diags, m); %Q=(-1/12*diag(ones(m-2,1),2)+8/12*diag(ones(m-1,1),1)-8/12*diag(ones(m-1,1),-1)+1/12*diag(ones(m-2,1),-2)); e_1=sparse(m,1);e_1(1)=1; e_m=sparse(m,1);e_m(m)=1; D1=H\(Q-1/2*(e_1*e_1')+1/2*(e_m*e_m')) ; %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % Second derivative, 1st order accurate at first 6 boundary points % m1=-1;m0=2; % % M=m1*(diag(ones(m-1,1),1)+diag(ones(m-1,1),-1))+m0*diag(ones(m,1),0);M(1,1)=1;M(m,m)=1; % stencil = [m2,m1,m0,m1,m2]; % d = (length(stencil)-1)/2; % diags = -d:d; % M = stripeMatrix(stencil, diags, m); % M=M/h; S_U=[-1 1]/h; S_1=sparse(1,m); S_1(1:2)=S_U; S_m=sparse(1,m); S_m(m-1:m)=fliplr(-S_U); % D2=H\(-M-e_1*S_1+e_m*S_m); %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % Third derivative, 1st order accurate at first 6 boundary points % q2=1/2;q1=-1; % % Q3=q2*(diag(ones(m-2,1),2)-diag(ones(m-2,1),-2))+q1*(diag(ones(m-1,1),1)-diag(ones(m-1,1),-1)); % stencil = [-q2,-q1,0,q1,q2]; % d = (length(stencil)-1)/2; % diags = -d:d; % Q3 = stripeMatrix(stencil, diags, m); %QQ3=(-1/8*diag(ones(m-3,1),3) + 1*diag(ones(m-2,1),2) - 13/8*diag(ones(m-1,1),1) +13/8*diag(ones(m-1,1),-1) -1*diag(ones(m-2,1),-2) + 1/8*diag(ones(m-3,1),-3)); % Q3_U = [0 -0.2e1 / 0.5e1 0.3e1 / 0.10e2 0.1e1 / 0.10e2; 0.2e1 / 0.5e1 0 -0.7e1 / 0.10e2 0.3e1 / 0.10e2; -0.3e1 / 0.10e2 0.7e1 / 0.10e2 0 -0.9e1 / 0.10e2; -0.1e1 / 0.10e2 -0.3e1 / 0.10e2 0.9e1 / 0.10e2 0;]; % Q3(1:4,1:4)=Q3_U; % Q3(m-3:m,m-3:m)=rot90( -Q3_U ,2 ); % Q3=Q3/h^2; S2_U=[1 -2 1;]/h^2; S2_1=sparse(1,m); S2_1(1:3)=S2_U; S2_m=sparse(1,m); S2_m(m-2:m)=fliplr(S2_U); % D3=H\(Q3 - e_1*S2_1 + e_m*S2_m +1/2*(S_1'*S_1) -1/2*(S_m'*S_m) ) ; % Fourth derivative, 0th order accurate at first 6 boundary points (still % yield 4th order convergence if stable: for example u_tt=-u_xxxx m2=1;m1=-4;m0=6; M4=m2*(diag(ones(m-2,1),2)+diag(ones(m-2,1),-2))+m1*(diag(ones(m-1,1),1)+diag(ones(m-1,1),-1))+m0*diag(ones(m,1),0); %M4=(-1/6*(diag(ones(m-3,1),3)+diag(ones(m-3,1),-3) ) + 2*(diag(ones(m-2,1),2)+diag(ones(m-2,1),-2)) -13/2*(diag(ones(m-1,1),1)+diag(ones(m-1,1),-1)) + 28/3*diag(ones(m,1),0)); M4_U=[0.4e1 / 0.5e1 -0.7e1 / 0.5e1 0.2e1 / 0.5e1 0.1e1 / 0.5e1; -0.7e1 / 0.5e1 0.16e2 / 0.5e1 -0.11e2 / 0.5e1 0.2e1 / 0.5e1; 0.2e1 / 0.5e1 -0.11e2 / 0.5e1 0.21e2 / 0.5e1 -0.17e2 / 0.5e1; 0.1e1 / 0.5e1 0.2e1 / 0.5e1 -0.17e2 / 0.5e1 0.29e2 / 0.5e1;]; M4(1:4,1:4)=M4_U; M4(m-3:m,m-3:m)=rot90( M4_U ,2 ); M4=M4/h^3; S3_U=[-1 3 -3 1;]/h^3; S3_1=sparse(1,m); S3_1(1:4)=S3_U; S3_m=sparse(1,m); S3_m(m-3:m)=fliplr(-S3_U); D4=H\(M4-e_1*S3_1+e_m*S3_m + S_1'*S2_1-S_m'*S2_m); S_1 = S_1'; S_m = S_m'; S2_1 = S2_1'; S2_m = S2_m'; S3_1 = S3_1'; S3_m = S3_m'; % L=h*(m-1); % x1=linspace(0,L,m)'; % x2=x1.^2/fac(2); % x3=x1.^3/fac(3); % x4=x1.^4/fac(4); % x5=x1.^5/fac(5); % x0=x1.^0/fac(1); end