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Homework Help: Lu Decomposition in C

  1. Dec 29, 2012 #1
    Hey, I have this code for lu decomposition but It doesn't quite work. If anyone could help me with the problem I'd be very appreciative.

    Code (Text):
    for(j=0; j<N; j++)
                    for(i=j+1; i<N; i++)
                      U[i][j]=0;

            for(j=0; j<N; j++)
                    for(i=j+1; i<N; i++)
                            L[j][i]=0;

            for(i=0; i<N; i++)
              U[i][i]=1;
              for(i=0; i<N; i++)
              L[i][0]=A[i][0];

            for(j=1; j<N; j++)
                    U[0][j]=A[0][j]/A[0][0];

            for(i=0; i<N; i++)
            {
                    for(j=0; j<=i; j++)
                    {
                            sum=0;
                            for(k=0; k<j; k++)
                                    sum+=(L[i][k]*U[k][j]);
                            L[i][j]=A[i][j]-sum;
                    }
                    for(j=N-1; j>=i; j--)
                    {
                          if(j!=0)
                            {
                            sum=0;
                            for(k=0; k<i; k++)
                                    sum+=(L[i][k]*U[k][j]);
                            if(L[i][i]!=0)
                                    U[i][j]=(A[i][j]-sum)/L[i][i];
                            }
                    }
            }
     
    Last edited: Dec 29, 2012
  2. jcsd
  3. Dec 29, 2012 #2

    phinds

    User Avatar
    Gold Member

    While there is still time to edit your post, put code tags around it so that it is readable.
     
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