Performance test script for https://github.com/ericniebler/meta/pull/3

perf_test.py

#!/usr/bin/env python

import os
import subprocess
import tempfile

for n in xrange(100, 2001, 100):
  with tempfile.NamedTemporaryFile(suffix='.cpp') as f:
    f.write('#include <type_traits>\n')
    f.write('#include <meta/meta.hpp>\n')
    f.write('\n')
    for x in xrange(n):
      f.write('class T{} {{}};\n'.format(x))
    f.write('\n')
    l = 'meta::list<{}>'.format(', '.join('T{}'.format(x) for x in xrange(n)))
    f.write('static_assert(std::is_same<meta::unique<{0}>, {0}>::value, "");\n'.format(l))
    f.write('\n')
    f.write('int main() {}\n')
    f.flush()
  
    result = subprocess.check_output(
        ['time',
         'clang++', 
         '-std=c++11', 
         '-ftemplate-depth=2048',
         '-I{}'.format(os.path.join(os.getcwd(), '../include')),
         '-o',
         '/dev/null',
         f.name],
        stderr=subprocess.STDOUT)

    print n, '\t\t', result.strip()

unique.md

% cd <meta>/test
% wget https://gist.githubusercontent.com/mpark/3c5d7cda5af76067f090/raw/1df2bbe3fe4f5e3e489b68fcc3e7ed4442878ea6/perf_test.py

% git checkout master
% python perf_test.py
100     0.27 real         0.23 user         0.02 sys
200     1.50 real         1.35 user         0.14 sys
300     4.94 real         4.46 user         0.46 sys
400     11.39 real        10.31 user        1.04 sys
500     20.25 real        18.37 user        1.86 sys
600     37.66 real        33.40 user        3.64 sys
700     62.53 real        54.46 user        6.62 sys
800     104.65 real       85.94 user        13.21 sys
^C

% git checkout unique
% python perf_test.py
100 		0.08 real         0.06 user         0.01 sys
200 		0.17 real         0.15 user         0.01 sys
300 		0.32 real         0.28 user         0.02 sys
400 		0.50 real         0.45 user         0.04 sys
500 		0.81 real         0.74 user         0.06 sys
600 		1.17 real         1.06 user         0.10 sys
700 		1.52 real         1.38 user         0.11 sys
800 		1.91 real         1.75 user         0.15 sys
900 		2.54 real         2.33 user         0.19 sys
1000 		3.27 real         2.99 user         0.26 sys
1100 		3.93 real         3.62 user         0.29 sys
1200 		4.41 real         4.07 user         0.33 sys
1300 		5.15 real         4.76 user         0.36 sys
1400 		6.23 real         5.77 user         0.44 sys
1500 		7.30 real         6.76 user         0.52 sys
1600 		8.40 real         7.80 user         0.58 sys
1700 		9.92 real         9.18 user         0.71 sys
1800 		10.82 real        10.06 user        0.74 sys
1900 		12.82 real        11.92 user        0.86 sys
2000 		14.24 real        13.25 user        0.94 sys