/
gaussj.C
123 lines (104 loc) · 2.48 KB
/
gaussj.C
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// gaussj.C
//
// <http://www-ee.eng.hawaii.edu/Courses/EE150/Book/chap9/section2.1.5.html>
#define BUILD_DLL
#include "gaussj.h"
#define DEBUG_MESSAGES
#ifdef DEBUG_MESSAGES
#include "mathlib.h"
#include "assertion.h"
#include <sstream>
#endif
void
GaussJordan::uptriangle ()
{
for (int k = 0; k < size; k++)
{
find_pivot (k);
process_column (k);
}
}
void
GaussJordan::process_column (const int k)
{
for (int i = k + 1; i < size; i++)
{
const double m = -get_entry (i, k) / get_entry (k, k);
for (int j = k; j < size; j++)
set_entry (i, j, get_entry (i, j) + m * get_entry (k, j));
value[i] += m * value[k];
}
}
void
GaussJordan::find_pivot (const int k)
{
if (iszero (get_entry (k, k)))
swap_rows (k, find_nonzero (k));
}
int
GaussJordan::find_nonzero (const int k)
{
for (int i = k; i < size; i++)
if (std::isnormal (get_entry (i, k)))
return i;
throw ("GaussJordan: Dependent equations.");
}
void
GaussJordan::swap_rows (const int k, const int j)
{
for (int i = k; i < size; i++)
{
const double tmp = get_entry (k, i);
set_entry (k, i, get_entry (j, i));
set_entry (j, i, tmp);
}
const double tmp = value[j];
value[j] = value[k];
value[k] = tmp;
}
void
GaussJordan::set_value (int row, double v)
{ value[row] = v; }
double
GaussJordan::get_value (int row) const
{ return value[row]; }
void
GaussJordan::set_entry (int row, int column, double v)
{ matrix[row * size + column] = v; }
double
GaussJordan::get_entry (int row, int column) const
{ return matrix[row * size + column]; }
void
GaussJordan::solve ()
{
uptriangle ();
for (int i = size - 1; i >= 0; i--)
{
double sum = 0;
for (int j = i+1; j < size; j++)
sum += get_entry (i, j) * result_[j];
const double entry = get_entry (i, i);
if (iszero (entry))
throw ("GaussJordan: zero solution");
#ifdef DEBUG_MESSAGES
if (!std::isfinite (entry) || !std::isfinite (value[i]) || !std::isfinite (sum))
throw ("GaussJordan: non-finite number");
if (fabs (entry) < 1e-100)
{
std::ostringstream tmp;
tmp << "GaussJordan[" << i << "," << i << "] = " << entry
<< ", value = " << value[i] << ", sum = " << sum;
Assertion::message (tmp.str ());
}
#endif
result_[i] = (value[i] - sum) / entry;
}
}
double GaussJordan::result (int row) const
{ return result_[row]; }
GaussJordan::GaussJordan (int s)
: size (s),
matrix (size * size),
value (size),
result_ (size)
{ }