void gaussj(MatDoub_IO &a, MatDoub_IO &b)
{
Int i,icol,irow,j,k,l,ll,n=a.nrows(),m=b.ncols();
Doub big,dum,pivinv;
VecInt indxc(n),indxr(n),ipiv(n);
for (j=0;j<n;j++) ipiv[j]=0;
for (i=0;i<n;i++) {
big=0.0;
for (j=0;j<n;j++)
if (ipiv[j] != 1)
for (k=0;k<n;k++) {
if (ipiv[k] == 0) {
if (abs(a[j][k]) >= big) {
big=abs(a[j][k]);
irow=j;
icol=k;
}
}
}
++(ipiv[icol]);
if (irow != icol) {
for (l=0;l<n;l++) SWAP(a[irow][l],a[icol][l]);
for (l=0;l<m;l++) SWAP(b[irow][l],b[icol][l]);
}
indxr[i]=irow;
indxc[i]=icol;
if (a[icol][icol] == 0.0) Throw1WithMessage("gaussj: Singular Matrix");
pivinv=1.0/a[icol][icol];
a[icol][icol]=1.0;
for (l=0;l<n;l++) a[icol][l] *= pivinv;
for (l=0;l<m;l++) b[icol][l] *= pivinv;
for (ll=0;ll<n;ll++)
if (ll != icol) {
dum=a[ll][icol];
a[ll][icol]=0.0;
for (l=0;l<n;l++) a[ll][l] -= a[icol][l]*dum;
for (l=0;l<m;l++) b[ll][l] -= b[icol][l]*dum;
}
}
for (l=n-1;l>=0;l--) {
if (indxr[l] != indxc[l])
for (k=0;k<n;k++)
SWAP(a[k][indxr[l]],a[k][indxc[l]]);
}
}
// From Numerical Recipes Ch 2
void gaussj(MatDoub_IO &a) {
MatDoub b(a.nrows(), 0);
gaussj(a, b);
}
