pydata/pandas — pull request #7463 by jreback (2014-06-14 20:12:21+00:00)
Title: PERF: performance gains in DataFrame groupby.transform for ufuncs (GH7383)

accelerates non-modifying transformations, e.g.

``DataFrame.groupby(...).transform(np.max)``

```
-------------------------------------------------------------------------------
Test name | head[ms] | base[ms] | ratio |
-------------------------------------------------------------------------------
groupby_transform_ufunc | 6.1977 | 215.6494 | 0.0287 |
groupby_transform2 | 155.9653 | 155.1824 | 1.0050 |
groupby_transform | 167.5134 | 165.7823 | 1.0104 |
-------------------------------------------------------------------------------
Test name | head[ms] | base[ms] | ratio |
-------------------------------------------------------------------------------

Ratio < 1.0 means the target commit is faster then the baseline.
Seed used: 1234

Target [3d3715b] : WPI: fast tranform on DataFrame
Base [eb1ae6b] : Merge pull request #7458 from sinhrks/intersection
```