PROGRAM d2r1 (input,output,dfile);
(* driver program for subroutine GAUSSJ *)
LABEL 10,99;
CONST
   np=20;
   mp=20;
TYPE
   glnpbynp = ARRAY [1..np,1..np] OF real;
   glnpbymp = ARRAY [1..np,1..mp] OF real;
   glnp = ARRAY [1..np] of integer;
VAR
   j,k,l,m,n : integer;
   a,ai,u : glnpbynp;
   b,x,t : glnpbymp;
   dfile : text;

(*$I MODFILE.PAS *)
(*$I GAUSSJ.PAS *)

BEGIN
   glopen(dfile,'matrx1.dat');
10:   readln(dfile);
   readln(dfile);
   readln(dfile,n,m);
   readln(dfile);
   FOR k := 1 to n DO BEGIN
      FOR l := 1 to n-1 DO read(dfile,a[k,l]);
      readln(dfile,a[k,n])
   END;
   readln(dfile);
   FOR l := 1 to m DO BEGIN
      FOR k := 1 to n-1 DO read(dfile,b[k,l]);
      readln(dfile,b[n,l])
   END;
(* save matrices for later testing of results *)
   FOR l := 1 to n DO BEGIN
      FOR k := 1 to n DO BEGIN
         ai[k,l] := a[k,l]
      END;
      FOR k := 1 to m DO BEGIN
         x[l,k] := b[l,k]
      END
   END;
(* invert matrix *)
   gaussj(ai,n,np,x,m,mp);
   writeln;
   writeln('Inverse of matrix a : ');
   FOR k := 1 to n DO BEGIN
      FOR l := 1 to n-1 DO write(ai[k,l]:12:6);
      writeln(ai[k,n]:12:6)
   END;
(* test results *)
(* check inverse *)
   writeln('a times a-inverse (compare with unit matrix)');
   FOR k := 1 to n DO BEGIN
      FOR l := 1 to n DO BEGIN
         u[k,l] := 0.0;
         FOR j := 1 to n DO BEGIN
            u[k,l] := u[k,l]+a[k,j]*ai[j,l]
         END
      END;
      FOR l := 1 to n-1 DO write(u[k,l]:12:6);
      writeln(u[k,n]:12:6)
   END;
(* check vector solutions *)
   writeln;
   writeln('Check the following vectors for equality:');
   writeln('original':20,'matrix*sol''n':15);
   FOR l := 1 to m DO BEGIN
   writeln('vector ',l:2,':');
      FOR k := 1 to n DO BEGIN
         t[k,l] := 0.0;
         FOR j := 1 to n DO BEGIN
            t[k,l] := t[k,l]+a[k,j]*x[j,l]
         END;
      writeln(' ':8,b[k,l]:12:6,t[k,l]:12:6);
      END
   END;
   writeln('***********************************');
   IF eof(dfile) THEN GOTO 99;
   writeln('press RETURN for next problem:');
   readln;
   GOTO 10;
99:   close(dfile)
END.