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hyperloglog.h
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1 /*
2  * hyperloglog.h
3  *
4  * A simple HyperLogLog cardinality estimator implementation
5  *
6  * Portions Copyright (c) 2014-2017, PostgreSQL Global Development Group
7  *
8  * Based on Hideaki Ohno's C++ implementation. The copyright terms of Ohno's
9  * original version (the MIT license) follow.
10  *
11  * src/include/lib/hyperloglog.h
12  */
13 
14 /*
15  * Copyright (c) 2013 Hideaki Ohno <hide.o.j55{at}gmail.com>
16  *
17  * Permission is hereby granted, free of charge, to any person obtaining a copy
18  * of this software and associated documentation files (the 'Software'), to
19  * deal in the Software without restriction, including without limitation the
20  * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
21  * sell copies of the Software, and to permit persons to whom the Software is
22  * furnished to do so, subject to the following conditions:
23  *
24  * The above copyright notice and this permission notice shall be included in
25  * all copies or substantial portions of the Software.
26  *
27  * THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
28  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
29  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
30  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
31  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
32  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
33  * IN THE SOFTWARE.
34  */
35 
36 #ifndef HYPERLOGLOG_H
37 #define HYPERLOGLOG_H
38 
39 /*
40  * HyperLogLog is an approximate technique for computing the number of distinct
41  * entries in a set. Importantly, it does this by using a fixed amount of
42  * memory. See the 2007 paper "HyperLogLog: the analysis of a near-optimal
43  * cardinality estimation algorithm" for more.
44  *
45  * hyperLogLogState
46  *
47  * registerWidth register width, in bits ("k")
48  * nRegisters number of registers
49  * alphaMM alpha * m ^ 2 (see initHyperLogLog())
50  * hashesArr array of hashes
51  * arrSize size of hashesArr
52  */
53 typedef struct hyperLogLogState
54 {
57  double alphaMM;
61 
62 extern void initHyperLogLog(hyperLogLogState *cState, uint8 bwidth);
63 extern void initHyperLogLogError(hyperLogLogState *cState, double error);
64 extern void addHyperLogLog(hyperLogLogState *cState, uint32 hash);
65 extern double estimateHyperLogLog(hyperLogLogState *cState);
66 extern void freeHyperLogLog(hyperLogLogState *cState);
67 
68 #endif /* HYPERLOGLOG_H */
static void error(void)
Definition: sql-dyntest.c:147
uint8 * hashesArr
Definition: hyperloglog.h:58
unsigned char uint8
Definition: c.h:304
void initHyperLogLogError(hyperLogLogState *cState, double error)
Definition: hyperloglog.c:127
double estimateHyperLogLog(hyperLogLogState *cState)
Definition: hyperloglog.c:185
unsigned int uint32
Definition: c.h:306
void freeHyperLogLog(hyperLogLogState *cState)
Definition: hyperloglog.c:150
void addHyperLogLog(hyperLogLogState *cState, uint32 hash)
Definition: hyperloglog.c:166
void initHyperLogLog(hyperLogLogState *cState, uint8 bwidth)
Definition: hyperloglog.c:65
struct hyperLogLogState hyperLogLogState
size_t Size
Definition: c.h:414
static unsigned hash(unsigned *uv, int n)
Definition: rege_dfa.c:541