Linear Equation

by vinays Fri Aug 20, 2010 8:27 pm

This doesn't work.....Vinay will repost this Snippet after debugging.

Code:: import java.io.*; class Linear_equations { public static void main(String args[]) { int j,i,n; DataInputStream in=new DataInputStream(System.in); try { System.out.println("What is the size of the system [ n<10 ]"); n=Integer.parseInt(in.readLine()); double x[]=new double[n]; double b[]=new double[n]; double a[][]=new double[n][n]; System.out.println("Enter co-efficients a[i , j] ,row-wise."); for(i=0;i<n;i++) { System.out.println("Row "+(i+1)); for(j=0;j<n;j++) a[i][j]=Double.valueOf(in.readLine()).floatValue(); } System.out.println("Input vector b"); for(j=0;j<n;j++) b[j]=Double.valueOf(in.readLine()).floatValue(); int index[]=new int[n]; x=Gaussian(a,b,index); System.out.println("Solution vector X "); for(i=0;i<n;i++) System.out.println(x[i]+" "); } catch(Exception e) { System.out.println("Exceptional Error occured! "); } } public static double[] Gaussian(double a[][],double b[],int index[]) { int n=b.length; double x[]=new double[n]; gaussian(a,index); for(int i=0;i<n;++i) { for(int j=i+1;j<n;++j) { b[index[j]]-=a[index[j]][i]*b[index[i]]; } } x[n-1]=b[index[n-1]]/a[index[n-1]][n-1]; for(int i=n-2;i>=0;--i) { x[i]=b[index[i]]; for(int j=i+1;j<n;++j) { x[i]-=a[index[i]][j]*x[j]; } x[i]/=a[index[i]][i]; } order(x,index); return x; } public static void gaussian(double a[][],int index[]) { int n=index.length; double c[]=new double[n]; for(int i=0;i<n;++i) index[i]=i; for(int i=0;i<n;++i) { double c1=0; for(int j=0;j<n;++j) { double c0=Math.abs(a[i][j]); if(c0>c1) c1=c0; } c[i]=c1; } int k=0; for(int j=0;j<n-1;++j) { double pi1=0; for(int i=j;i<n;++i) { double pi0=Math.abs(a[index[i]][j]); pi0/=c[index[i]]; if(pi0>pi1) { pi1=pi0; k=i; } } int itmp=index[j]; index[j]=index[k]; index[k]=itmp; for(int i=j+1;i<n;++i) { double pj=a[index[i]][j]/a[index[j]][i]; a[index[i]][j]=pj; for(int l=j+1;l<n;++l) a[index[i]][l]-=pj*a[index[j]][l]; } } } public static void order(double x[],int index[]) { int m=x.length; for(int i=0;i<m;++i) { if(index[i]>index[j]) { int itmp=index[i]; index[i]=index[j]; index[j]=itmp; double xtmp=x[i]; x[i]=x[j]; x[j]=xtmp; } } } }