Results of bench_pow2.py on Linux.

Common platform:
CPU model: Intel(R) Core(TM) i7-3520M CPU @ 2.90GHz
Platform: Linux-3.13.9-200.fc20.x86_64-x86_64-with-fedora-20-Heisenbug
Timer: time.perf_counter
Python unicode implementation: PEP 393
Timer info: namespace(adjustable=False, implementation='clock_gettime(CLOCK_MONOTONIC)', monotonic=True, resolution=1e-09)
CFLAGS: -Wno-unused-result -Werror=declaration-after-statement -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes
Bits: int=32, long=64, long long=64, size_t=64, void*=64

Platform of campaign orig:
Date: 2014-05-02 23:45:29
SCM: hg revision=62438d1b11c7 tag=tip branch=default date="2014-05-02 23:26 +0200"
Timer precision: 49 ns
Python version: 3.5.0a0 (default:62438d1b11c7, May 2 2014, 23:45:22) [GCC 4.8.2 20131212 (Red Hat 4.8.2-7)]

Platform of campaign pow2:
Python version: 3.5.0a0 (default:62438d1b11c7+, May 2 2014, 23:47:50) [GCC 4.8.2 20131212 (Red Hat 4.8.2-7)]
SCM: hg revision=62438d1b11c7+ tag=tip branch=default date="2014-05-02 23:26 +0200"
Timer precision: 51 ns
Date: 2014-05-02 23:48:03

---------------+--------------+----------------
Tests          |         orig |            pow2
---------------+--------------+----------------
2 ** 0         |    40 ns (*) |     44 ns (+9%)
2 ** 1         |   264 ns (*) |    62 ns (-76%)
2 ** 3         |   270 ns (*) |    62 ns (-77%)
2 ** 5         |   269 ns (*) |    62 ns (-77%)
2 ** 10        |   278 ns (*) |    63 ns (-78%)
2 ** 15        |   299 ns (*) |    62 ns (-79%)
2 ** 20        |   287 ns (*) |    62 ns (-78%)
2 ** 25        |   302 ns (*) |    62 ns (-79%)
2 ** 28        |   293 ns (*) |    62 ns (-79%)
2 ** (2 ** 0)  |   264 ns (*) |    62 ns (-77%)
2 ** (2 ** 1)  |   264 ns (*) |    62 ns (-76%)
2 ** (2 ** 3)  |   264 ns (*) |    62 ns (-77%)
2 ** (2 ** 5)  |   286 ns (*) |    68 ns (-76%)
2 ** (2 ** 10) |   740 ns (*) |    68 ns (-91%)
2 ** (2 ** 15) |  93.1 us (*) |  180 ns (-100%)
2 ** (2 ** 20) |  3.94 ms (*) | 3.89 us (-100%)
2 ** (2 ** 25) |   154 ms (*) |  213 us (-100%)
2 ** (2 ** 28) | 1.36 sec (*) | 4.01 ms (-100%)
---------------+--------------+----------------
Total          | 1.52 sec (*) | 4.23 ms (-100%)
---------------+--------------+----------------