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Thread: Bairstow metod help
 07112012, 04:30 AM #1Member
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Bairstow metod help
Hi i need help to make this code work I'm new in java and its a exam for a class of math and i get some errors
if need hears a link to the math code
Bairstow's method  Wikipedia, the free encyclopedia
thanks
Java Code:public class fiz_app { public static void main(String[] args) { double a[] ={1.25,3.875,2.125,2.75,3.5,1}; int n = a.length; double re[] = new double [n]; double im[] = new double [n]; Bairstow(a,1,1,1,1,1,re,im,3); } public static void Bairstow(double a[],int nn,int es,double rr, double ss, int maxit, double im[],double re[], int iter ) { double dr; double ds; double b[] = new double[nn]; double c[] = new double[nn]; double r, s, det, ea1, ea2; int n, i; r = rr; s = ss; n = nn; iter = 0; ea1 = 1; ea2 = 1; Object r1; Object i1; Object r2; Object i2; while(n<3  iter >= maxit) { iter = 0; do { iter = iter +1; b[n] = a[n]; b[n  1] = a[n  1] +r * b[n]; c[n] = b[n]; c[n  1] = b[n  1] +r * c[n]; for(i=(n2); i >=0; i=i1) { b[i] = a[i] +r * b[i+1] +s * b[i +2]; c[i] = b[i] +r * c[i1] +s * c[i +2]; } det = c[2] * c[2]c[3] * c[1]; if(det != 0.0) { dr = (b[1] * c[2] +b[0] * c[3])/det; ds = (b[0] * c[2] +b[1] * c[1])/det; r = r +dr; s = s +ds; if(r != 0) ea1 = Math.abs(dr/r)*100; if(s != 0) ea2 = Math.abs(ds/s)*100; } else { r = r +1; s = s +1; iter = 0; } }while(!(ea1 <= es && ea2 <= es  iter >= maxit)); Quadroot(r,s,r1,i1,r2,i2); re[n] = r1; im[n] = i1; re[n  1] = r2; im[n  1] = i2; n = n2; for(i=0; i<n; i++) { a[i] = b[i +2]; } } if( iter < maxit) { if( n == 2) { r = a[1]/a[2]; s = a[0]/a[2]; Quadroot(r,s,r1,i1,r2,i2); re[n] = r1; im[n] = i1; re[n  1] = r2; im[n  1] = i2; } else { re[n] = a[0]/a[1]; im[n] = 0; } } else iter = 1; }//Bairstow public static void Quadroot(double r, double s, double r1, double i1, double r2, double i2) { double disc; disc = r* r + 4 * s; if( disc > 0) { r1 = (r + Math.sqrt(disc))/2; r2 = (r  Math.sqrt(disc))/2; i1 = 0; i2 = 0; } else { r1 = r/2; r2 = r1; i1 = Math.sqrt(Math.abs(disc))/2; i2 = i1; } }// QuadRoot }
 07112012, 08:28 AM #2
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Re: Bairstow metod help
That code came from a Fortran worlds, right? For nasty iterative methods like that, System.out.println( ... ) is your friend. Print out everything you suspect to be incorrect for each iteration and check those values; it's a tedious job and you have to go through it.
kind regards,
Joscenosillicaphobia: the fear for an empty beer glass
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