MinCircle2<Real>::MinCircle2 (int numPoints, const Vector2<Real>* points,
Circle2<Real>& minimal, Real epsilon)
:
mEpsilon(epsilon)
{
mUpdate[0] = 0;
mUpdate[1] = &MinCircle2<Real>::UpdateSupport1;
mUpdate[2] = &MinCircle2<Real>::UpdateSupport2;
mUpdate[3] = &MinCircle2<Real>::UpdateSupport3;
Support support;
Real distDiff;
if (numPoints >= 1)
{
// Create identity permutation (0,1,...,numPoints-1).
Vector2<Real>** permuted = new1<Vector2<Real>*>(numPoints);
int i;
for (i = 0; i < numPoints; ++i)
{
permuted[i] = (Vector2<Real>*)&points[i];
}
// Generate random permutation.
for (i = numPoints - 1; i > 0; --i)
{
int j = rand() % (i+1);
if (j != i)
{
Vector2<Real>* save = permuted[i];
permuted[i] = permuted[j];
permuted[j] = save;
}
}
minimal = ExactCircle1(*permuted[0]);
support.Quantity = 1;
support.Index[0] = 0;
// The previous version of the processing loop is
// i = 1;
// while (i < numPoints)
// {
// if (!support.Contains(i, permuted, mEpsilon))
// {
// if (!Contains(*permuted[i], minimal, distDiff))
// {
// UpdateFunction update = mUpdate[support.Quantity];
// Circle2<Real> circle = (this->*update)(i, permuted,
// support);
// if (circle.Radius > minimal.Radius)
// {
// minimal = circle;
// i = 0;
// continue;
// }
// }
// }
// ++i;
// }
// This loop restarts from the beginning of the point list each time
// the circle needs updating. Linus Källberg (Computer Science at
// Mälardalen University in Sweden) discovered that performance is
// better when the remaining points in the array are processed before
// restarting. The points processed before the point that caused the
// update are likely to be enclosed by the new circle (or near the
// circle boundary) because they were enclosed by the previous circle.
// The chances are better that points after the current one will cause
// growth of the bounding circle.
for (int i = 1 % numPoints, n = 0; i != n; i = (i + 1) % numPoints)
{
if (!support.Contains(i, permuted, mEpsilon))
{
if (!Contains(*permuted[i], minimal, distDiff))
{
UpdateFunction update = mUpdate[support.Quantity];
Circle2<Real> circle =(this->*update)(i, permuted,
support);
if (circle.Radius > minimal.Radius)
{
minimal = circle;
n = i;
}
}
}
}
delete1(permuted);
}
else
{
assertion(false, "Input must contain points\n");
}
minimal.Radius = Math<Real>::Sqrt(minimal.Radius);
}
MinCircle2<Real>::MinCircle2 ( int numPoints, const Vector2<Real>* points,
Circle2<Real>& minimal, Real epsilon )
:
mEpsilon( epsilon )
{
mUpdate[0] = 0;
mUpdate[1] = &MinCircle2<Real>::UpdateSupport1;
mUpdate[2] = &MinCircle2<Real>::UpdateSupport2;
mUpdate[3] = &MinCircle2<Real>::UpdateSupport3;
Support support;
Real distDiff;
if ( numPoints >= 1 )
{
// Create identity permutation (0,1,...,numPoints-1).
Vector2<Real>** permuted = new1<Vector2<Real>*>( numPoints );
int i;
for ( i = 0; i < numPoints; ++i )
{
permuted[i] = ( Vector2<Real>* )&points[i];
}
// Generate random permutation.
for ( i = numPoints - 1; i > 0; --i )
{
int j = rand() % ( i + 1 );
if ( j != i )
{
Vector2<Real>* save = permuted[i];
permuted[i] = permuted[j];
permuted[j] = save;
}
}
minimal = ExactCircle1( *permuted[0] );
support.Quantity = 1;
support.Index[0] = 0;
i = 1;
while ( i < numPoints )
{
if ( !support.Contains( i, permuted, mEpsilon ) )
{
if ( !Contains( *permuted[i], minimal, distDiff ) )
{
UpdateFunction update = mUpdate[support.Quantity];
Circle2<Real> circle = ( this->*update )( i, permuted,
support );
if ( circle.Radius > minimal.Radius )
{
minimal = circle;
i = 0;
continue;
}
}
}
++i;
}
delete1( permuted );
}
else
{
assertion( false, "Input must contain points\n" );
}
minimal.Radius = Math<Real>::Sqrt( minimal.Radius );
}
