ASKIT has lower accuracy while using more neighbors

[ChenhanYu]

#nbors GOFMM ASKIT
2 1.5E0 4.5E-3
16 3.7E-1 4.1E-1
32 3.7E-1 4.5E-1

[ChenhanYu]

For GOFMM, using more neighbors may not help. But ASKIT should always be more accurate. One possible issue is that the 50% of pruning list has been swapped with the sampling list. If I can reproduce this result, I will take a look at it.

[ChenhanYu]

We will need a concrete example to reproduce this bug.