bdiff: don't check border condition in loop
This is pretty much a copy of d500ddae7494, just to a different loop.
The condition `p == plast` (`plast == a + len - 1`) was only true on
the final iteration of the loop. So it was wasteful to check for it
on every iteration. We decrease the iteration count by 1 and add an
explicit check for `p == plast` after the loop.
Again, we see modest wins.
From the mozilla-unified repository:
$ perfbdiff -m 3041e4d59df2
! wall 0.035502 comb 0.040000 user 0.040000 sys 0.000000 (best of 100)
! wall 0.030480 comb 0.030000 user 0.030000 sys 0.000000 (best of 100)
$ perfbdiff 0e9928989e9c --alldata --count 100
! wall 4.097394 comb 4.100000 user 4.100000 sys 0.000000 (best of 3)
! wall 3.597798 comb 3.600000 user 3.600000 sys 0.000000 (best of 3)
The 2nd example throws a total of ~3.3GB of data at bdiff. This
change increases the throughput from ~811 MB/s to ~924 MB/s.
#!/usr/bin/env python
#
# A portable replacement for 'seq'
#
# Usage:
# seq STOP [1, STOP] stepping by 1
# seq START STOP [START, STOP] stepping by 1
# seq START STEP STOP [START, STOP] stepping by STEP
from __future__ import absolute_import, print_function
import sys
start = 1
if len(sys.argv) > 2:
start = int(sys.argv[1])
step = 1
if len(sys.argv) > 3:
step = int(sys.argv[2])
stop = int(sys.argv[-1]) + 1
for i in xrange(start, stop, step):
print(i)