185 lines
No EOL
3.1 KiB
C++
Executable file
185 lines
No EOL
3.1 KiB
C++
Executable file
// Authors: Unknown. Please, if you are the author of this file, or if you
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// know who are the authors of this file, let us know, so we can give the
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// adequate credits and/or get the adequate authorizations.
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#include "numerics1.h"
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float **allocate_float_matrix(int nrows, int ncols)
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{
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float ** matrix;
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matrix = new float*[nrows];
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for(int i=0; i < nrows; i++) matrix[i] = new float[ncols];
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return matrix;
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}
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void desallocate_float_matrix(float **matrix, int nrows, int ncols)
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{
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if (matrix == NULL) return;
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for(int i=0; i < nrows; i++) { delete[] matrix[i]; matrix[i] = 0;}
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matrix = 0;
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ncols = ncols; // to remove the warning unused parameter ¡®ncols¡¯
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}
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// **********************************************
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// LU based algorithms
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// **********************************************
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// Solves Ax=b by using lu decomposition
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int lusolve(float **a, float *x, float *b, int n)
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{
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float d;
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int *indx = new int[n];
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if (ludcmp(a,n,indx,&d))
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{
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for(int i=0; i < n; i++) x[i] = b[i];
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lubksb(a,n,indx,x);
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delete[] indx; /*memcheck*/
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return 1;
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} else
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{
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printf("lusolve::lu decomposition failed\n");
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delete[] indx; /*memcheck*/
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return 0;
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}
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delete[] indx; // Guoshen Yu
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}
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int ludcmp(float **a, int n, int *indx, float *d)
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{
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int i,imax=0,j,k,aux;
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float big,dum,sum,temp;
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float *vv;
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vv=(float *) malloc(n*sizeof(float));
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*d=1.0;
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for(i=0;i<n;i++) indx[i]=i;
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/**** Look for the largest value of every line and store 1/this value****/
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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 ( (temp=fabs(a[i][j]))>big ) big=temp;
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if (big==0.0) { return 0; printf("LU Decomposition failed\n");}
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vv[i]=1.0/big;
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}
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for(j=0;j<n;j++){
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for(i=0;i<j;i++){
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sum=a[i][j];
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for(k=0;k<i;k++) sum-= a[i][k]*a[k][j];
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a[i][j]=sum;
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}
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big=0.0;
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for(i=j;i<n;i++){
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sum=a[i][j];
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for(k=0;k<j;k++)
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sum -=a[i][k]*a[k][j];
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a[i][j]=sum;
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if ( (dum=vv[i]*fabs(sum))>=big){
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big=dum;
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imax=i;
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}
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}
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if (j != imax){
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for(k=0;k<n;k++){
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dum=a[imax][k];
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a[imax][k]=a[j][k];
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a[j][k]=dum;
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}
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*d=-(*d);
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vv[imax]=vv[j];
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aux=indx[j];
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indx[j]=indx[imax];
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indx[imax]=aux;
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}
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if (a[j][j]==0.0) a[j][j]=NRTINY;
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if (j!=n-1 ){
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dum=1.0 / a[j][j];
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for(i=j+1;i<n;i++) a[i][j]*=dum;
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}
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}
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free(vv);
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return 1;
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}
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/* Solves the set of n linear equations Ax=b. Here a[0..n-1][0..n-1] as input, not as the matrix A but rather as its LU decomposition,*/
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/* determined by the routine ludcmp. indx[0..n-1] is input as the permutation vector returned by ludcmp. b[0..n-1] is input as the */
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/* right hand side vector and returns with the solution vector x. */
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void lubksb(float **a, int n, int *indx, float *b)
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{
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int i,ii=0,j;
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float sum,*aux;
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aux= (float *) malloc(n*sizeof(float));
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for(i=0;i<n;i++)
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aux[i]=b[indx[i]];
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for(i=0;i<n;i++){
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sum=aux[i];
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if (ii)
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for(j=ii-1;j<i;j++) sum-=a[i][j]*aux[j];
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else if (sum) ii=i+1;
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aux[i]=sum;
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}
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for(i=n-1;i>=0;i--){
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sum=aux[i];
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for(j=i+1;j<n;j++) sum-=a[i][j]*aux[j];
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aux[i]=sum/a[i][i];
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b[i]=sum/a[i][i];
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}
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free(aux);
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} |