public double TestSpeedNative()
{
d_native a = new d_native(1), b = new d_native(2), c = new d_native(3);
var sum = new d_native(0);
for (var i = 0; i < N; i++)
{
sum += a * b + c;
a = b + c;
b = c + a;
}
return(sum.val);
}
private static extern void d_div(ref d_native self, ref d_native val);
public void Managed_Pinvoke()
{
var m = new Matrix <d_native>(N);
var b = new d_native[N];
var x = new d_native[N];
var size = N;
var zero = new d_native(0);
var one = new d_native(1);
d_native Abs(d_native val)
{
return(val.val > 0 ? val : new d_native(-val.val));
}
for (var i = 0; i < size - 1; i++)
{
// Search for maximum in this column
var maxEl = Abs(m[i, i]);
var maxRow = i;
for (var k = i + 1; k < size; k++)
{
if (Abs(m[k, i]) > maxEl)
{
maxEl = Abs(m[k, i]);
maxRow = k;
}
}
// Swap maximum row with current row (column by column)
for (var k = i; k < size; k++)
{
var tmp = m[maxRow, k];
m[maxRow, k] = m[i, k];
m[i, k] = tmp;
}
// swap in b vector
{
var tmp = b[maxRow];
b[maxRow] = b[i];
b[i] = tmp;
}
// eliminate current variable in all columns
for (var k = i + 1; k < size; k++)
{
var c = zero - m[k, i] / m[i, i];
for (var j = i; j < size; j++)
{
if (i == j)
{
m[k, j] = zero;
}
else
{
m[k, j] += c * m[i, j];
}
}
// b vector
b[k] += c * b[i];
}
}
// Solve equation Ax=b for an upper triangular matrix A
for (var i = size - 1; i >= 0; i--)
{
if (b[i] == zero)
{
continue;
}
// normalize
b[i] /= m[i, i];
m[i, i] = one;
// backward elimination
for (var k = i - 1; k >= 0; k--)
{
b[k] -= m[k, i] * b[i];
m[k, i] = zero;
}
}
b.CopyTo(x, 0);
}
