bsd/dev/dtrace/dtrace_xoroshiro128_plus.c

   1 /*-
   2  * Copyright (c) 2016 (Graeme Jenkinson)
   3  * All rights reserved.
   4  *
   5  * This software was developed by BAE Systems, the University of Cambridge
   6  * Computer Laboratory, and Memorial University under DARPA/AFRL contract
   7  * FA8650-15-C-7558 ("CADETS"), as part of the DARPA Transparent Computing
   8  * (TC) research program.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  29  * SUCH DAMAGE.
  30  *
  31  */
  32
  33 #include <sys/types.h>
  34
  35 #include "dtrace_xoroshiro128_plus.h"
  36
  37 static __inline uint64_t
  38 rotl(const uint64_t x, int k)
  39 {
  40         return (x << k) | (x >> (64 - k));
  41 }
  42
  43 /*
  44  * This is the jump function for the generator. It is equivalent to 2^64 calls
  45  * to next(); it can be used to generate 2^64 non-overlapping subsequences for
  46  * parallel computations.
  47  */
  48 void
  49 dtrace_xoroshiro128_plus_jump(uint64_t * const state,
  50     uint64_t * const jump_state)
  51 {
  52         static const uint64_t JUMP[] = { 0xbeac0467eba5facb,
  53                                          0xd86b048b86aa9922 };
  54
  55         uint64_t s0 = 0;
  56         uint64_t s1 = 0;
  57         size_t i = 0;
  58         int b = 0;
  59         for (i = 0; i < sizeof JUMP / sizeof *JUMP; i++) {
  60                 for (b = 0; b < 64; b++) {
  61                         if (JUMP[i] & 1ULL << b) {
  62                                 s0 ^= state[0];
  63                                 s1 ^= state[1];
  64                         }
  65                         dtrace_xoroshiro128_plus_next(state);
  66                 }
  67         }
  68         jump_state[0] = s0;
  69         jump_state[1] = s1;
  70 }
  71
  72 /*
  73  * xoroshiro128+ - XOR/rotate/shift/rotate
  74  * xorshift.di.unimi.it
  75  */
  76 uint64_t
  77 dtrace_xoroshiro128_plus_next(uint64_t * const state)
  78 {
  79         const uint64_t s0 = state[0];
  80         uint64_t s1 = state[1];
  81         uint64_t result;
  82         result = s0 + s1;
  83
  84         s1 ^= s0;
  85         state[0] = rotl(s0, 55) ^ s1 ^ (s1 << 14);
  86         state[1] = rotl(s1, 36);
  87
  88         return result;
  89 }