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.
/**
* Copyright (c) 2016-present, Gregory Szorc
* All rights reserved.
*
* This software may be modified and distributed under the terms
* of the BSD license. See the LICENSE file for details.
*/
#include "python-zstandard.h"
PyDoc_STRVAR(DictParameters__doc__,
"DictParameters: low-level control over dictionary generation");
static PyObject* DictParameters_new(PyTypeObject* subtype, PyObject* args, PyObject* kwargs) {
DictParametersObject* self;
unsigned selectivityLevel;
int compressionLevel;
unsigned notificationLevel;
unsigned dictID;
if (!PyArg_ParseTuple(args, "IiII", &selectivityLevel, &compressionLevel,
¬ificationLevel, &dictID)) {
return NULL;
}
self = (DictParametersObject*)subtype->tp_alloc(subtype, 1);
if (!self) {
return NULL;
}
self->selectivityLevel = selectivityLevel;
self->compressionLevel = compressionLevel;
self->notificationLevel = notificationLevel;
self->dictID = dictID;
return (PyObject*)self;
}
static void DictParameters_dealloc(PyObject* self) {
PyObject_Del(self);
}
static Py_ssize_t DictParameters_length(PyObject* self) {
return 4;
};
static PyObject* DictParameters_item(PyObject* o, Py_ssize_t i) {
DictParametersObject* self = (DictParametersObject*)o;
switch (i) {
case 0:
return PyLong_FromLong(self->selectivityLevel);
case 1:
return PyLong_FromLong(self->compressionLevel);
case 2:
return PyLong_FromLong(self->notificationLevel);
case 3:
return PyLong_FromLong(self->dictID);
default:
PyErr_SetString(PyExc_IndexError, "index out of range");
return NULL;
}
}
static PySequenceMethods DictParameters_sq = {
DictParameters_length, /* sq_length */
0, /* sq_concat */
0, /* sq_repeat */
DictParameters_item, /* sq_item */
0, /* sq_ass_item */
0, /* sq_contains */
0, /* sq_inplace_concat */
0 /* sq_inplace_repeat */
};
PyTypeObject DictParametersType = {
PyVarObject_HEAD_INIT(NULL, 0)
"DictParameters", /* tp_name */
sizeof(DictParametersObject), /* tp_basicsize */
0, /* tp_itemsize */
(destructor)DictParameters_dealloc, /* tp_dealloc */
0, /* tp_print */
0, /* tp_getattr */
0, /* tp_setattr */
0, /* tp_compare */
0, /* tp_repr */
0, /* tp_as_number */
&DictParameters_sq, /* tp_as_sequence */
0, /* tp_as_mapping */
0, /* tp_hash */
0, /* tp_call */
0, /* tp_str */
0, /* tp_getattro */
0, /* tp_setattro */
0, /* tp_as_buffer */
Py_TPFLAGS_DEFAULT, /* tp_flags */
DictParameters__doc__, /* tp_doc */
0, /* tp_traverse */
0, /* tp_clear */
0, /* tp_richcompare */
0, /* tp_weaklistoffset */
0, /* tp_iter */
0, /* tp_iternext */
0, /* tp_methods */
0, /* tp_members */
0, /* tp_getset */
0, /* tp_base */
0, /* tp_dict */
0, /* tp_descr_get */
0, /* tp_descr_set */
0, /* tp_dictoffset */
0, /* tp_init */
0, /* tp_alloc */
DictParameters_new, /* tp_new */
};
void dictparams_module_init(PyObject* mod) {
Py_TYPE(&DictParametersType) = &PyType_Type;
if (PyType_Ready(&DictParametersType) < 0) {
return;
}
Py_IncRef((PyObject*)&DictParametersType);
PyModule_AddObject(mod, "DictParameters", (PyObject*)&DictParametersType);
}