Why 2 partitions in 1 iteration?

[chaohuang]

In the function CIsochartEngine::PartitionByGlobalAvgL2Stretch inside file isochartengine.cpp, there are 2 function calls to perform chart partition in the do while loop: one is ParameterizeChartsInHeapParallelized which calls pChart->Partition(), and the other one is GenerateNewChartsToParameterize which calls pChartWithMaxL2Stretch->Bipartition3D().

So my question is why calling 2 partitions in every 1 iteration of the do while loop. What if only Partition() or Bipartition3D() is called? And what's the difference between Partition() and Bipartition3D()?

Thanks.