void subtractMultipleTo(DMat<RT>& C,
const DMat<RT>& A,
const DMat<RT>& B)
// C = C - A*B
{
typedef typename RT::ElementType ElementType;
typedef typename DMat<RT>::ConstIterator ConstIterator;
M2_ASSERT(A.numColumns() == B.numRows());
M2_ASSERT(A.numRows() == C.numRows());
M2_ASSERT(B.numColumns() == C.numColumns());
ElementType* result = C.array();
ElementType tmp;
A.ring().init(tmp);
// WARNING: this routine expects the result matrix to be in ROW MAJOR ORDER
for (size_t i = 0; i<A.numRows(); i++)
for (size_t j = 0; j<B.numColumns(); j++)
{
ConstIterator i1 = A.rowBegin(i);
ConstIterator iend = A.rowEnd(i);
ConstIterator j1 = B.columnBegin(j);
while (i1 != iend)
{
A.ring().mult(tmp, *i1, *j1);
A.ring().subtract(*result, *result, tmp);
++i1;
++j1;
}
result++;
}
A.ring().clear(tmp);
}
void mult(const DMat<RT>& A,
const DMat<RT>& B,
DMat<RT>& result_product)
{
//printf("entering dmat mult\n");
typedef typename RT::ElementType ElementType;
typedef typename DMat<RT>::ConstIterator ConstIterator;
M2_ASSERT(A.numColumns() == B.numRows());
M2_ASSERT(A.numRows() == result_product.numRows());
M2_ASSERT(B.numColumns() == result_product.numColumns());
ElementType* result = result_product.array();
ElementType tmp;
A.ring().init(tmp);
// WARNING: this routine expects the result matrix to be in ROW MAJOR ORDER
for (size_t i = 0; i<A.numRows(); i++)
for (size_t j = 0; j<B.numColumns(); j++)
{
ConstIterator i1 = A.rowBegin(i);
ConstIterator iend = A.rowEnd(i);
ConstIterator j1 = B.columnBegin(j);
while (i1 != iend)
{
A.ring().mult(tmp, *i1, *j1);
A.ring().add(*result, *result, tmp);
++i1;
++j1;
}
result++;
}
A.ring().clear(tmp);
}
void transpose(const DMat<RT>& A, DMat<RT>& result)
{
assert(&A != &result); // these cannot be aliased!
assert(result.numRows() == A.numColumns());
assert(result.numColumns() == A.numRows());
for (size_t c = 0; c < A.numColumns(); ++c)
{
auto i = A.columnBegin(c);
auto j = result.rowBegin(c);
auto end = A.columnEnd(c);
for (; i != end; ++i, ++j) A.ring().set(*j, *i);
}
}
