private static void subtractRow(EquationRow u, EquationRow v, double m, int k, int n)
{
for (int i = k; i <= n; i++)
{
u.coeff[i] -= m * v.coeff[i];
}
u.b -= m * v.b;
}
public static bool solve(EquationRow[] equations, double[] x, int n)
{
const double assumedzero = 1e-30;
//int n = equations.Length-1;
//x = null;
for (int j = 0; j < n; j++)
{
swapPivRow(equations, j, n);
EquationRow pivotalrow = equations[j];
double pivot = pivotalrow.coeff[j];
if (Math.Abs(pivot) <= assumedzero)
{
return(false);
}
for (int i = j + 1; i <= n; i++)
{
double mult = equations[i].coeff[j] / pivot;
if (Math.Abs(mult) > assumedzero)
{
equations[i].coeff[j] = mult;
subtractRow(equations[i], pivotalrow, mult, j + 1, n);
}
else
{
equations[i].coeff[j] = 0;
}
}
}
bool result = Math.Abs(equations[n].coeff[n]) > assumedzero;
if (result)
{
//x = new double[equations.Length];
x[n] = equations[n].b / equations[n].coeff[n];
for (int i = n - 1; i >= 0; i--)
{
double top = equations[i].b;
for (int k = i + 1; k <= n; k++)
{
top -= equations[i].coeff[k] * x[k];
}
x[i] = top / equations[i].coeff[i];
}
}
return(result);
}
private static void swapPivRow(EquationRow[] a, int col, int n)
{
double max = Math.Abs(a[col].coeff[col]);
int pivi = col;
for (int i = col + 1; i <= n; i++)
{
if (Math.Abs(a[i].coeff[col]) > max)
{
max = Math.Abs(a[i].coeff[col]);
pivi = i;
}
}
if (pivi != col)
{
EquationRow rowp = a[col];
a[col] = a[pivi];
a[pivi] = rowp;
}
}
