Implement Method Gauss Jordan Elimination in Delphi

Question

This is my homework from my school to make Gauss-jordan elimination in delphi, but..I got some problem here...

I Made like this :

procedure TForm1.Button3Click(Sender: TObject);
var
  n,i,j,k,bar,kol:integer;
  a:array [1..100,1..100]of real;
  x:array [1..100]of real;
  faktor:real;
begin
  memo1.Clear;
  n:=stringgrid2.RowCount-1;
  kenalmatriks;
  StringGrid2.RowCount := baris;
  StringGrid2.ColCount := kolom;

  for i:=1 to n do
  begin
    for j:=1 to n+1 do
    begin
      a[i,j]:=strtofloat(stringgrid1.cells[j,i]);
    end;
  end;

  for k:=1 to n do
  begin
    faktor:=a[k,k];
    for j:=1 to n+1 do
    begin
      a[j,k]:=a[j,k]/faktor;
    end;
    for i:=1 to n do
    begin
      if i<>k then
      begin
        faktor:=a[i,k];
        for j:=1 to n+1 do
        begin
          a[i,j]:=a[i,j]-faktor*a[k,j];
        end;
      end;
    end;
  end;

  for bar:=1 to n do
  begin
    for kol:=1 to n+1 do
    begin
      stringgrid2.cells[kol,bar]:=floattostr(a[bar,kol]);
    end;
  end;
end;

The result must like this :

1   0   0   2
0   1   0   7
0   0   1   -3

But, mine :

--   --   --   --
--   1    0    15.33
--   0    1    2

I hope I can finish this... :( anyone...please help...

Answer 1

Disclaimer: I don't know anything about Gauss-jordan elimination and never heard of it.

The answer is clear though!

Either your math is off, or you are grabbing the wrong numbers.

As was suggested by manuell in the first comment to your post, you need to see what numbers are being used.

A simple way to debug in console that I use is: writeln('whatever variable: ' + VARIABLE).

you can use a MemoList if you are in a GUI development to do the same thing. You will be surprised of the results sometimes.

Also use the right functions for what you want floatToStr and strToFloat are not what you want probably.

Edit:

Looked up Gauss-jordan elimination also known as row reduction and it turns out to be simple matrices algebra.

I never knew that is what is called likely because although attributed to Gauss, it was already known to Chinese mathematicians in 179 AD.

A good example is found here: http://www.youtube.com/watch?v=Xc37YM59vVA

A good example in Delphi, although written in an earlier version: Delphi-3 programming language, with source code is found here

Another example but has much more than Gaussian elimination so you have to look at the code can be found here

Here is an example in C++

So now I am sure you have solved it or lost your login to SO. Good luck and enjoy the process as that is the best part.