/usr/share/octave/packages/bim-1.1.5/bim2a_reaction.m is in octave-bim 1.1.5-4.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 | ## Copyright (C) 2006,2007,2008,2009,2010 Carlo de Falco, Massimiliano Culpo
##
## This file is part of:
## BIM - Diffusion Advection Reaction PDE Solver
##
## BIM is free software; you can redistribute it and/or modify
## it under the terms of the GNU General Public License as published by
## the Free Software Foundation; either version 2 of the License, or
## (at your option) any later version.
##
## BIM is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with BIM; If not, see <http://www.gnu.org/licenses/>.
##
## author: Carlo de Falco <cdf _AT_ users.sourceforge.net>
## author: Massimiliano Culpo <culpo _AT_ users.sourceforge.net>
## -*- texinfo -*-
## @deftypefn {Function File} {[@var{C}]} = @
## bim2a_reaction(@var{mesh},@var{delta},@var{zeta})
##
## Build the lumped finite element mass matrix for a diffusion
## problem.
##
## The equation taken into account is:
##
## @var{delta} * @var{zeta} * u = f
##
## where @var{delta} is an element-wise constant scalar function, while
## @var{zeta} is a piecewise linear conforming scalar function.
##
## @seealso{bim2a_rhs, bim2a_advection_diffusion, bim2a_laplacian,
## bim1a_reaction, bim3a_reaction}
## @end deftypefn
function [C] = bim2a_reaction(mesh,delta,zeta)
## Check input
if nargin != 3
error("bim2a_reaction: wrong number of input parameters.");
elseif !(isstruct(mesh) && isfield(mesh,"p") &&
isfield (mesh,"t") && isfield(mesh,"e"))
error("bim2a_reaction: first input is not a valid mesh structure.");
endif
nnodes = size(mesh.p,2);
nelem = size(mesh.t,2);
## Turn scalar input to a vector of appropriate size
if isscalar(delta)
delta = delta*ones(nelem,1);
endif
if isscalar(zeta)
zeta = zeta*ones(nnodes,1);
endif
if !( isvector(delta) && isvector(zeta) )
error("bim2a_reaction: coefficients are not valid vectors.");
elseif (numel (delta) != nelem)
error("bim2a_: length of alpha is not equal to the number of elements.");
elseif (numel (zeta) != nnodes)
error("bim2a_: length of gamma is not equal to the number of nodes.");
endif
wjacdet = mesh.wjacdet(:,:);
coeff = zeta(mesh.t(1:3,:));
coeffe = delta(:);
## Local matrix
Blocmat = zeros(3,nelem);
for inode = 1:3
Blocmat(inode,:) = coeffe'.*coeff(inode,:).*wjacdet(inode,:);
endfor
gnode = (mesh.t(1:3,:));
## Global matrix
C = sparse(gnode(:),gnode(:),Blocmat(:));
endfunction
%!shared mesh,delta,zeta,nnodes,nelem
% x = y = linspace(0,1,4);
% [mesh] = msh2m_structured_mesh(x,y,,1:4;
% [mesh] = bim2c_mesh_properties(mesh);
% nnodes = columns(mesh.p);
% nelem = columns(mesh.t);
% delta = ones(columns(mesh.t),1);
% zeta = ones(columns(mesh.p),1);
%!test
% [C] = bim2a_reaction(mesh,delta,zeta);
% assert(size(C),[nnodes, nnodes]);
%!test
% [C1] = bim2a_reaction(mesh,3*delta,zeta);
% [C2] = bim2a_reaction(mesh,delta,3*zeta);
% assert(C1,C2);
%!test
% [C1] = bim2a_reaction(mesh,3*delta,zeta);
% [C2] = bim2a_reaction(mesh,3,1);
% assert(C1,C2);
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