110 lines
2.7 KiB
C++
110 lines
2.7 KiB
C++
/*
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LA: linear algebra C++ interface library
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Copyright (C) 2021 Jiri Pittner <jiri.pittner@jh-inst.cas.cz> or <jiri@pittnerovi.com>
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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//this header defines some simple algorithms independent of external libraries
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//particularly intended to embedded computers
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//it should be compilable separately from LA as well as being a part of LA
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#ifndef _SIMPLE_H_
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#define _SIMPLE_H_
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#include <stdlib.h>
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#ifndef AVOID_STDSTREAM
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#include <iostream>
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#endif
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#include <string.h>
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#include <math.h>
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#include <stdio.h>
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namespace LA_Simple {
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//a simple gauss elimination as a template also for larger-size matrices in form of C-style arrays
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#define SWAP(a,b) {T temp=(a);(a)=(b);(b)=temp;}
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template<typename T, int n, int m>
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T simple_gaussj(T (&a)[n][n],T (&b)[m][n]) //returns determinant, m is number of rhs to solve
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{
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int indxc[n],indxr[n],ipiv[n];
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int i,icol,irow,j,k,l,ll;
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T det,big,dum,pivinv;
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det=1;
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for (j=0;j<n;j++) ipiv[j]=0;
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for (i=0;i<n;i++) {
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big=0.0;
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for (j=0;j<n;j++)
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if (ipiv[j] != 1)
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for (k=0;k<n;k++) {
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if (ipiv[k] == 0) {
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if (abs(a[j][k]) >= big) {
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big=abs(a[j][k]);
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irow=j;
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icol=k;
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}
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} else if (ipiv[k] > 1) {return 0;}
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}
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++(ipiv[icol]);
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if (irow != icol) {
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det = (-det);
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for (l=0;l<n;l++) SWAP(a[irow][l],a[icol][l])
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for (l=0;l<m;l++) SWAP(b[l][irow],b[l][icol])
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}
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indxr[i]=irow;
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indxc[i]=icol;
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if (a[icol][icol] == 0) {return 0;}
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pivinv=1/a[icol][icol];
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det *= a[icol][icol];
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a[icol][icol]=1.0;
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for (l=0;l<n;l++) a[icol][l] *= pivinv;
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for (l=0;l<m;l++) b[l][icol] *= pivinv;
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for (ll=0;ll<n;ll++)
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if (ll != icol) {
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dum=a[ll][icol];
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a[ll][icol]=0.0;
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for (l=0;l<n;l++) a[ll][l] -= a[icol][l]*dum;
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for (l=0;l<m;l++) b[l][ll] -= b[l][icol]*dum;
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}
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}
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for (l=n-1;l>=0;l--) {
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if (indxr[l] != indxc[l])
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for (k=0;k<n;k++)
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SWAP(a[k][indxr[l]],a[k][indxc[l]]);
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}
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return det;
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}
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#undef SWAP
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template<typename T, int n>
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class simple_linfit {
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T mata[n][n];
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T matb[1][n];
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public:
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};
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//stream I/O
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#ifndef AVOID_STDSTREAM
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#endif
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}//namespace
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#endif /* _SIMPLE_H_ */
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