c++ to php conversion

Question

I have wroted a LU writed in c++ and I need add same code to php i did it it's woarks but in php i have diffrent results. Main calculate in c++ are:

 for (int i=0;i<m;i++)
    {
         for (int j=0;j<m;j++)
         {
             cout << tab1[i][j]<<"\t";    
         }   
         cout <<endl;
    }

      for (int i=0;i<m;i++)
    {
         for (int j=0;j<m;j++)
         {

             if (i==j) 
              {
                       tab2[i][j]=1;
                       tab3[i][j]=0;
                       }
              else
              {
                       tab3[i][j]=0;
                       tab2[i][j]=0;
                       }

         }   
    }
       //glowne dzielenie tego co mamy do rozlozenia
    for (int i=0;i<m;i++)
    {   

        for (int j=0;j<m;j++)
        {
            for (int k=0;k<m;k++)
            {
                pom+=tab2[i][k]*tab3[k][j];   
                pomoc+=tab2[j][k]*tab3[k][i];    
            }    
           if (i<=j)
            tab3[i][j]=tab1[i][j]-pom;

           if (j>=i)
            tab2[j][i]=(tab1[j][i]-pomoc)/tab3[i][i];

            pom=0;
            pomoc=0;
        }    
    }

and in php it looks:

 $w= sizeof($this->input['macierz_1']);
     $pom=0;   $pomoc=0;

                for ($i=1;$i<=$w;$i++)
          {
             for ($j=1;$j<=$w;$j++)
              {

                  if ($i==$j) 
                  {
                             $tab2[$i][$j]=1;
                             $tab3[$i][$j]=0;
                             }
                 else
                  {
                             $tab3[$i][$j]=0;
                             $tab2[$i][$j]=0;
                             }

              }   
          }

        //glowne dzielenie tego co mamy do rozlozenia
        for ($i=1;$i<=$w;$i++)
         {   
            for ($j=1;$j<=$w;$j++)
             {
                 for ($k=1;$k<=$w;$k++)
                  {
                     $pom+=$tab2[$i][$k]*$tab3[$k][$j];  
                     $pomoc+=$tab2[$j][$k]*$tab3[$k][$i];


         }    
                 if ($i<=$j)
          $tab3[$i][$j]=($this->input['macierz_1'][$i][$j])-$pom;


                 if ($j>=$i)

                 $tab2[$j][$i]=(($this->input['macierz_1'][$i][$j])-$pomoc)/$tab3[$i][$i];


                 $pom=0;
                 $pomoc=0;

             }    
         }
       echo '<b>Macierz wynikowa L:<br> </b>';
     $this->formularz($w,$w,'macierz_L',$tab2);
        echo '<b>Macierz wynikowa U: <br> </b>';
     $this->formularz($w,$w,'macierz_U',$tab3);
        }

I know that i started arry in php form 1 not 0 and in all algorym its ok. Can any one tell me where i maked mastake or give algorytm LU in php that it woarks?

Answer 1

1. What is an LU?
2. What exactly do you mean with mistake. Runtime error, unexpected output, program does not terminate?

At first glance, your PHP code looks correctly for me.

You have to be a bit more clearly, otherwise people are having a hard time to help you.

Answer 2

1. LU it is numeric metod with Lover and Upper decay. It is familiar with Gauus elimination for array.
2. I dont have eny errorrs progrm run but results are not thta what should be. They are diffrent

Answer 3

Does this example help? http://au.php.net/manual/en/function.array.php#49054

michael dot bommarito at gmail dot com

15-Jan-2005 03:14

Just in case anyone else was looking for some help writing an LU decomposition function, here's a simple example.

N.B. All arrays are assumed to begin with index 1, not 0. This is not hard to change, but make sure you specify array(1=>...), not just array(...).

Furthermore, this function is optimized to only consider variable elements of the matrices. As $L will be a lower triangular matrix, there is no need to compute the elements of either the diagonal or the upper triangle; likewise with $U.

This function also does not check to verify that the input matrix is non-singular.

/*
 * LU Decomposition
 * @param $A initial matrix (1...m x 1...n)
 * @param $L lower triangular matrix, passed by reference
 * @param $U upper triangular matrix, passed by reference
*/
function LUDecompose($A, &$L, &$U) 
{
    $m = sizeof($A);
    $n = sizeof($A[1]);

    for ( $i = 1; $i <= $m; $i++ ) {
        $U[$i][$i] = $A[$i][$i];

        for ( $j = $i + 1; $j <= $m; $j++ ) {
            $L[$j][$i] = $A[$j][$i] / $U[$i][$i];
            $U[$i][$j] = $A[$i][$j];
        }
        for ( $j = $i + 1; $j <= $m; $j++ ) {
            for ( $k = $i + 1; $k <= $m; $k++ ) {
              $A[$j][$k] = $A[$j][$k] - ($L[$j][$i] * $U[$i][$k]);
            }
        }
    }

    return;
}