private void DivideAndConquer(ArrayList groupBucket, double[] gaps, double threshold, int a, int b)
{
// First, check for trivial recursion
// (for example, if there's only one element in range).
if (a == b)
{
// Add group (of one) to bucket, and pop back up the stack.
IndexValueCouplet[] group = new IndexValueCouplet[1];
Array.Copy(this.svalues, a, group, 0, 1);
groupBucket.Add(group);
return;
}
// Find the two biggest gaps (or biggest single gap, if there's only
// two points in this range).
System.Diagnostics.Debug.Assert(gaps.Length > 0);
int biggest = -1; int biggest2 = -1;
for (int i = a; i < b; ++i)
{
if (biggest < 0 || gaps[i] > gaps[biggest])
{
biggest2 = biggest; biggest = i;
}
else if (biggest2 < 0 || gaps[i] > gaps[biggest2])
{
biggest2 = i;
}
}
if (biggest2 < 0)
{
biggest2 = biggest;
}
// Only split further if one of the following two conditions is met:
// - range > 2x specified threshold, or
// - range > 1x threshold, and there exists an obvious split point
// (say, a gap 1.5x bigger than any other).
double range = svalues[b].value - svalues[a].value;
double gapSizeRatio = gaps[biggest] / gaps[biggest2];
if ((range > 2 * threshold) || (range > 1 * threshold && gapSizeRatio > 1.5))
{
// Split on the biggest single gap.
DivideAndConquer(groupBucket, gaps, threshold, a, biggest);
DivideAndConquer(groupBucket, gaps, threshold, biggest + 1, b);
}
else
{
// Add group to bucket, and pop back up the stack.
int n = b - a + 1;
IndexValueCouplet[] group = new IndexValueCouplet[n];
Array.Copy(this.svalues, a, group, 0, n);
groupBucket.Add(group);
return;
}
}
public ScalarPartitioning(double[] values)
{
int n = values.Length;
// Plot the values on a number line (in other words, sort them).
// But retain the ordering of the items, for later re-ordering.
this.svalues = new IndexValueCouplet[n];
for (int i=0; i < n; ++i)
svalues[i] = new IndexValueCouplet(i,values[i]);
Array.Sort(svalues,IndexValueCouplet.ByValue);
}
public int Compare(object x, object y)
{
IndexValueCouplet xx = (IndexValueCouplet)x;
IndexValueCouplet yy = (IndexValueCouplet)y;
if (xx.value == yy.value)
{
return(0);
}
else
{
return((xx.value < yy.value) ? -1 : +1);
}
}
public ScalarPartitioning(double[] values)
{
int n = values.Length;
// Plot the values on a number line (in other words, sort them).
// But retain the ordering of the items, for later re-ordering.
this.svalues = new IndexValueCouplet[n];
for (int i = 0; i < n; ++i)
{
svalues[i] = new IndexValueCouplet(i, values[i]);
}
Array.Sort(svalues, IndexValueCouplet.ByValue);
}
private void DivideAndConquer(ArrayList groupBucket, double[] gaps, double threshold, int a, int b)
{
// First, check for trivial recursion
// (for example, if there's only one element in range).
if (a == b)
{
// Add group (of one) to bucket, and pop back up the stack.
IndexValueCouplet[] group = new IndexValueCouplet[1];
Array.Copy(this.svalues,a,group,0,1);
groupBucket.Add(group);
return;
}
// Find the two biggest gaps (or biggest single gap, if there's only
// two points in this range).
System.Diagnostics.Debug.Assert(gaps.Length > 0);
int biggest = -1; int biggest2 = -1;
for (int i=a; i < b; ++i)
{
if (biggest < 0 || gaps[i] > gaps[biggest])
{
biggest2 = biggest; biggest = i;
}
else if (biggest2 < 0 || gaps[i] > gaps[biggest2])
{
biggest2 = i;
}
}
if (biggest2 < 0) biggest2 = biggest;
// Only split further if one of the following two conditions is met:
// - range > 2x specified threshold, or
// - range > 1x threshold, and there exists an obvious split point
// (say, a gap 1.5x bigger than any other).
double range = svalues[b].value-svalues[a].value;
double gapSizeRatio = gaps[biggest]/gaps[biggest2];
if ((range > 2*threshold) || (range > 1*threshold && gapSizeRatio > 1.5))
{
// Split on the biggest single gap.
DivideAndConquer(groupBucket, gaps, threshold, a, biggest);
DivideAndConquer(groupBucket, gaps, threshold, biggest+1, b);
}
else
{
// Add group to bucket, and pop back up the stack.
int n = b-a+1;
IndexValueCouplet[] group = new IndexValueCouplet[n];
Array.Copy(this.svalues,a,group,0,n);
groupBucket.Add(group);
return;
}
}
