contrib/python-zstandard/zstd.c
author Gregory Szorc <gregory.szorc@gmail.com>
Sun, 20 Nov 2016 16:56:21 -0800
changeset 30461 d195fa651b51
parent 30435 b86a448a2965
child 30822 b54a2984cdd4
permissions -rw-r--r--
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.
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/**
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 * Copyright (c) 2016-present, Gregory Szorc
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 * All rights reserved.
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 *
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 * This software may be modified and distributed under the terms
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 * of the BSD license. See the LICENSE file for details.
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 */
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/* A Python C extension for Zstandard. */
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#include "python-zstandard.h"
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PyObject *ZstdError;
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PyDoc_STRVAR(estimate_compression_context_size__doc__,
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"estimate_compression_context_size(compression_parameters)\n"
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"\n"
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"Give the amount of memory allocated for a compression context given a\n"
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"CompressionParameters instance");
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PyDoc_STRVAR(estimate_decompression_context_size__doc__,
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"estimate_decompression_context_size()\n"
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"\n"
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"Estimate the amount of memory allocated to a decompression context.\n"
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);
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static PyObject* estimate_decompression_context_size(PyObject* self) {
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	return PyLong_FromSize_t(ZSTD_estimateDCtxSize());
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}
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PyDoc_STRVAR(get_compression_parameters__doc__,
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"get_compression_parameters(compression_level[, source_size[, dict_size]])\n"
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"\n"
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"Obtains a ``CompressionParameters`` instance from a compression level and\n"
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"optional input size and dictionary size");
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PyDoc_STRVAR(train_dictionary__doc__,
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"train_dictionary(dict_size, samples)\n"
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"\n"
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"Train a dictionary from sample data.\n"
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"\n"
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"A compression dictionary of size ``dict_size`` will be created from the\n"
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"iterable of samples provided by ``samples``.\n"
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"\n"
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"The raw dictionary content will be returned\n");
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static char zstd_doc[] = "Interface to zstandard";
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static PyMethodDef zstd_methods[] = {
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	{ "estimate_compression_context_size", (PyCFunction)estimate_compression_context_size,
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	METH_VARARGS, estimate_compression_context_size__doc__ },
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	{ "estimate_decompression_context_size", (PyCFunction)estimate_decompression_context_size,
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	METH_NOARGS, estimate_decompression_context_size__doc__ },
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	{ "get_compression_parameters", (PyCFunction)get_compression_parameters,
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	METH_VARARGS, get_compression_parameters__doc__ },
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	{ "train_dictionary", (PyCFunction)train_dictionary,
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	METH_VARARGS | METH_KEYWORDS, train_dictionary__doc__ },
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	{ NULL, NULL }
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};
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void compressobj_module_init(PyObject* mod);
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void compressor_module_init(PyObject* mod);
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void compressionparams_module_init(PyObject* mod);
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void constants_module_init(PyObject* mod);
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void dictparams_module_init(PyObject* mod);
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void compressiondict_module_init(PyObject* mod);
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void compressionwriter_module_init(PyObject* mod);
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void compressoriterator_module_init(PyObject* mod);
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void decompressor_module_init(PyObject* mod);
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void decompressobj_module_init(PyObject* mod);
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void decompressionwriter_module_init(PyObject* mod);
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void decompressoriterator_module_init(PyObject* mod);
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void zstd_module_init(PyObject* m) {
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	compressionparams_module_init(m);
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	dictparams_module_init(m);
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	compressiondict_module_init(m);
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	compressobj_module_init(m);
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	compressor_module_init(m);
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	compressionwriter_module_init(m);
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	compressoriterator_module_init(m);
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	constants_module_init(m);
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	decompressor_module_init(m);
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	decompressobj_module_init(m);
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	decompressionwriter_module_init(m);
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	decompressoriterator_module_init(m);
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}
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#if PY_MAJOR_VERSION >= 3
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static struct PyModuleDef zstd_module = {
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	PyModuleDef_HEAD_INIT,
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	"zstd",
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	zstd_doc,
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	-1,
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	zstd_methods
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};
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PyMODINIT_FUNC PyInit_zstd(void) {
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	PyObject *m = PyModule_Create(&zstd_module);
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	if (m) {
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		zstd_module_init(m);
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	}
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	return m;
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}
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#else
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PyMODINIT_FUNC initzstd(void) {
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	PyObject *m = Py_InitModule3("zstd", zstd_methods, zstd_doc);
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	if (m) {
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		zstd_module_init(m);
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	}
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}
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#endif