gaussian.java

数值计算（科学计算）实验代码高斯消元楚列斯基分解

import java.math.*;
public class Gaussian {
	public double[] Gaussian (double[][] a,double[] b,int n)
	{
		//void gaosi(double a[][n],double m[][n],double *x,double *b);
		

		    //double[][] a={{21.0,67.0,88.0,73.0},{76.0,63.0,7.0,20.0},{0.0,85.0,56.0,54.0},{19.3,43.0,30.2,29.4}};
			double[][] m=new double[n][n];
			double[] x=new double[n];
			//double[] b={141.0,109.0,218.0,93.7};
			//printf("The Matrix A is:\n");
			//int n=4;
			x=this.gaosi(a,m,x,b,n);
			return x;
		}
		double[] gaosi(double[][] a,double[][] m,double[] x,double[] b,int n)
		{
			int i,j,k;
			
			for(i=0;i<n;i++)
				for(j=0;j<n;j++)
					if(i==j) m[i][j]=1; else m[i][j]=0;
			for(k=0;k<n;k++)
			{
				if(a[k][k]==0) break;
				for(i=k+1;i<n;i++)
				{
					m[i][k]=a[i][k]/a[k][k];
					a[i][k]=0;
				}
				//printf("The %d M Matrix is:\n",k+1);
				/*for(i=0;i<n;i++)
				{
					for(j=0;j<n;j++)
				//			printf("%f\t",m[i][j]);
					printf("\n");
				}*/

				//printf("\n");
				for(j=k+1;j<n;j++)
					for(i=k+1;i<n;i++)
						a[i][j]-=m[i][k]*a[k][j];
				for(i=k+1;i<n;i++)
					b[i]-=m[i][k]*b[k];
				for(i=k+1;i<n;i++)
					m[i][k]=0;
			}
			for(j=n-1;j>=0;j--)
			{
				if(a[j][j]==0) break;
				x[j]=b[j]/a[j][j];
				for(i=0;i<=j-1;i++)
					b[i]-=a[i][j]*x[j];
			}
			for(j=0;j<n;j++)
			System.out.print("The result x"+(j+1)+"  is  "+x[j]+"\n");
			return x;
		}
 
}