void assign_src(const GI& g, std::vector<double>& src)
{
typedef typename GI::CellIterator CI;
int count = 0;
for (CI c = g.cellbegin(); c != g.cellend(); ++c) {
src[count++] = -Lu(c->centroid())*c->volume();
}
}
int LuSolve(
size_t n ,
size_t m ,
const FloatVector &A ,
const FloatVector &B ,
FloatVector &X ,
Float &logdet )
{
// check numeric type specifications
CheckNumericType<Float>();
// check simple vector class specifications
CheckSimpleVector<Float, FloatVector>();
size_t p; // index of pivot element (diagonal of L)
int signdet; // sign of the determinant
Float pivot; // pivot element
// the value zero
const Float zero(0);
// pivot row and column order in the matrix
std::vector<size_t> ip(n);
std::vector<size_t> jp(n);
// -------------------------------------------------------
CPPAD_ASSERT_KNOWN(
size_t(A.size()) == n * n,
"Error in LuSolve: A must have size equal to n * n"
);
CPPAD_ASSERT_KNOWN(
size_t(B.size()) == n * m,
"Error in LuSolve: B must have size equal to n * m"
);
CPPAD_ASSERT_KNOWN(
size_t(X.size()) == n * m,
"Error in LuSolve: X must have size equal to n * m"
);
// -------------------------------------------------------
// copy A so that it does not change
FloatVector Lu(A);
// copy B so that it does not change
X = B;
// Lu factor the matrix A
signdet = LuFactor(ip, jp, Lu);
// compute the log of the determinant
logdet = Float(0);
for(p = 0; p < n; p++)
{ // pivot using the max absolute element
pivot = Lu[ ip[p] * n + jp[p] ];
// check for determinant equal to zero
if( pivot == zero )
{ // abort the mission
logdet = Float(0);
return 0;
}
// update the determinant
if( LeqZero ( pivot ) )
{ logdet += log( - pivot );
signdet = - signdet;
}
else logdet += log( pivot );
}
// solve the linear equations
LuInvert(ip, jp, Lu, X);
// return the sign factor for the determinant
return signdet;
}
