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.
import io
try:
import unittest2 as unittest
except ImportError:
import unittest
try:
import hypothesis
import hypothesis.strategies as strategies
except ImportError:
hypothesis = None
import zstd
class TestCompressionParameters(unittest.TestCase):
def test_init_bad_arg_type(self):
with self.assertRaises(TypeError):
zstd.CompressionParameters()
with self.assertRaises(TypeError):
zstd.CompressionParameters(0, 1)
def test_bounds(self):
zstd.CompressionParameters(zstd.WINDOWLOG_MIN,
zstd.CHAINLOG_MIN,
zstd.HASHLOG_MIN,
zstd.SEARCHLOG_MIN,
zstd.SEARCHLENGTH_MIN,
zstd.TARGETLENGTH_MIN,
zstd.STRATEGY_FAST)
zstd.CompressionParameters(zstd.WINDOWLOG_MAX,
zstd.CHAINLOG_MAX,
zstd.HASHLOG_MAX,
zstd.SEARCHLOG_MAX,
zstd.SEARCHLENGTH_MAX,
zstd.TARGETLENGTH_MAX,
zstd.STRATEGY_BTOPT)
def test_get_compression_parameters(self):
p = zstd.get_compression_parameters(1)
self.assertIsInstance(p, zstd.CompressionParameters)
self.assertEqual(p[0], 19)
if hypothesis:
s_windowlog = strategies.integers(min_value=zstd.WINDOWLOG_MIN,
max_value=zstd.WINDOWLOG_MAX)
s_chainlog = strategies.integers(min_value=zstd.CHAINLOG_MIN,
max_value=zstd.CHAINLOG_MAX)
s_hashlog = strategies.integers(min_value=zstd.HASHLOG_MIN,
max_value=zstd.HASHLOG_MAX)
s_searchlog = strategies.integers(min_value=zstd.SEARCHLOG_MIN,
max_value=zstd.SEARCHLOG_MAX)
s_searchlength = strategies.integers(min_value=zstd.SEARCHLENGTH_MIN,
max_value=zstd.SEARCHLENGTH_MAX)
s_targetlength = strategies.integers(min_value=zstd.TARGETLENGTH_MIN,
max_value=zstd.TARGETLENGTH_MAX)
s_strategy = strategies.sampled_from((zstd.STRATEGY_FAST,
zstd.STRATEGY_DFAST,
zstd.STRATEGY_GREEDY,
zstd.STRATEGY_LAZY,
zstd.STRATEGY_LAZY2,
zstd.STRATEGY_BTLAZY2,
zstd.STRATEGY_BTOPT))
class TestCompressionParametersHypothesis(unittest.TestCase):
@hypothesis.given(s_windowlog, s_chainlog, s_hashlog, s_searchlog,
s_searchlength, s_targetlength, s_strategy)
def test_valid_init(self, windowlog, chainlog, hashlog, searchlog,
searchlength, targetlength, strategy):
p = zstd.CompressionParameters(windowlog, chainlog, hashlog,
searchlog, searchlength,
targetlength, strategy)
self.assertEqual(tuple(p),
(windowlog, chainlog, hashlog, searchlog,
searchlength, targetlength, strategy))
# Verify we can instantiate a compressor with the supplied values.
# ZSTD_checkCParams moves the goal posts on us from what's advertised
# in the constants. So move along with them.
if searchlength == zstd.SEARCHLENGTH_MIN and strategy in (zstd.STRATEGY_FAST, zstd.STRATEGY_GREEDY):
searchlength += 1
p = zstd.CompressionParameters(windowlog, chainlog, hashlog,
searchlog, searchlength,
targetlength, strategy)
elif searchlength == zstd.SEARCHLENGTH_MAX and strategy != zstd.STRATEGY_FAST:
searchlength -= 1
p = zstd.CompressionParameters(windowlog, chainlog, hashlog,
searchlog, searchlength,
targetlength, strategy)
cctx = zstd.ZstdCompressor(compression_params=p)
with cctx.write_to(io.BytesIO()):
pass
@hypothesis.given(s_windowlog, s_chainlog, s_hashlog, s_searchlog,
s_searchlength, s_targetlength, s_strategy)
def test_estimate_compression_context_size(self, windowlog, chainlog,
hashlog, searchlog,
searchlength, targetlength,
strategy):
p = zstd.CompressionParameters(windowlog, chainlog, hashlog,
searchlog, searchlength,
targetlength, strategy)
size = zstd.estimate_compression_context_size(p)