ClickHouse/libs/libconsistent-hashing/mailru/sumbur.cpp

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//Copyright (c) 2011-2012 Mail.RU
//Copyright (c) 2011-2012 Maksim Kalinchenko
//Copyright (c) 2012 Sokolov Yura aka funny-falcon
//
//MIT License
//
//Permission is hereby granted, free of charge, to any person obtaining
//a copy of this software and associated documentation files (the
//"Software"), to deal in the Software without restriction, including
//without limitation the rights to use, copy, modify, merge, publish,
//distribute, sublicense, and/or sell copies of the Software, and to
//permit persons to whom the Software is furnished to do so, subject to
//the following conditions:
//
//The above copyright notice and this permission notice shall be
//included in all copies or substantial portions of the Software.
//
//THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
//EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
//MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
//NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
//LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
//OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
//WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
#include <stdexcept>
#define L 0xFFFFFFFF
static unsigned int L27_38[] = {L / 27, L / 28, L / 29, L / 30, L / 31, L / 32,
L / 33, L / 34, L / 35, L / 36, L / 37, L / 38,
L / 39, L / 40, L / 41, L / 42, L / 43, L / 44,
L / 45, L / 46, L / 47, L / 48, L / 49, L / 50,
L / 51, L / 52, L / 53, L / 54, L / 55, L / 56,
L / 57, L / 58, L / 59, L / 60, L / 61, L / 62
};
static unsigned int LL27_38[] = {L/(26*27), L/(27*28), L/(28*29), L/(29*30), L/(30*31), L/(31*32),
L/(32*33), L/(33*34), L/(34*35), L/(35*36), L/(36*37), L/(37*38),
L/(38*39), L/(39*40), L/(40*41), L/(41*42), L/(42*43), L/(43*44),
L/(44*45), L/(45*46), L/(46*47), L/(47*48), L/(48*49), L/(49*50),
L/(50*51), L/(51*52), L/(52*53), L/(53*54), L/(54*55), L/(55*56),
L/(56*57), L/(57*58), L/(58*59), L/(59*60), L/(60*61), L/(61*62)
};
unsigned int sumburConsistentHash(unsigned int hashed_int, unsigned int capacity)
{
unsigned int h = hashed_int;
unsigned int capa = capacity;
unsigned int part, n, i, c;
if (capa == 0)
throw std::runtime_error("Sumbur is not applicable to empty cluster");
part = L / capa;
if (L - h < part) return 0;
n = 1;
do {
if (h >= L / 2) h -= L / 2;
else {
n = 2;
if (L / 2 - h < part) return 1;
}
if (capa == 2) return 1;
#define curslice(i) (L / (i * (i - 1)))
#define unroll(i) \
if (curslice(i) <= h) h -= curslice(i); \
else { \
h += curslice(i) * (i - n - 1); \
n = i; \
if (L / i - h < part) return n-1; \
} \
if (capa == i) return (n-1)
unroll(3); unroll(4); unroll(5);
unroll(6); unroll(7); unroll(8);
unroll(9); unroll(10); unroll(11);
unroll(12); unroll(13); unroll(14);
unroll(15); unroll(16); unroll(17);
unroll(18); unroll(19); unroll(20);
unroll(21); unroll(22); unroll(23);
unroll(24); unroll(25); unroll(26);
for (i = 27; i <= capa && i <= 62; i++) {
c = LL27_38[i-27];
if (c <= h) {
h -= c;
}
else {
h += c * (i - n - 1);
n = i;
if (L27_38[i-27] - h < part) return n-1;
}
}
for(i = 63; i <= capa; i++) {
c = L / (i * (i - 1));
if (c <= h) {
h -= c;
}
else {
h += c * (i - n - 1);
n = i;
if (L / i - h < part) return n - 1;
}
}
} while(0);
return n - 1;
}