FreeBSD/Linux Kernel Cross Reference
sys/cddl/contrib/opensolaris/uts/common/dtrace/dtrace_xoroshiro128_plus.c

     /*-
      * Copyright (c) 2016 (Graeme Jenkinson)
      * All rights reserved.
      *
      * This software was developed by BAE Systems, the University of Cambridge
      * Computer Laboratory, and Memorial University under DARPA/AFRL contract
      * FA8650-15-C-7558 ("CADETS"), as part of the DARPA Transparent Computing
      * (TC) research program.
      *
     * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     */
    
    #include <sys/types.h>
    
    #include "dtrace_xoroshiro128_plus.h"
    
    static __inline uint64_t
    rotl(const uint64_t x, int k)
    {
            return (x << k) | (x >> (64 - k));
    }
    
    /*
     * This is the jump function for the generator. It is equivalent to 2^64 calls
     * to next(); it can be used to generate 2^64 non-overlapping subsequences for
     * parallel computations.
     */
    void
    dtrace_xoroshiro128_plus_jump(uint64_t * const state,
            uint64_t * const jump_state)
    {
            static const uint64_t JUMP[] = { 0xbeac0467eba5facb,
                    0xd86b048b86aa9922 };
    
            uint64_t s0 = 0;
            uint64_t s1 = 0;
            int i = 0;
            int b = 0;
            for (i = 0; i < sizeof JUMP / sizeof *JUMP; i++) {
                    for (b = 0; b < 64; b++) {
                            if (JUMP[i] & 1ULL << b) {
                                    s0 ^= state[0];
                                    s1 ^= state[1];
                            }
                            dtrace_xoroshiro128_plus_next(state);
                    }
            }
            jump_state[0] = s0;
            jump_state[1] = s1;
    }
    
    /*
     * xoroshiro128+ - XOR/rotate/shift/rotate
     * xorshift.di.unimi.it
     */
    uint64_t
    dtrace_xoroshiro128_plus_next(uint64_t * const state)
    {
            const uint64_t s0 = state[0];
            uint64_t s1 = state[1];
            uint64_t result;
            result = s0 + s1;
    
            s1 ^= s0;
            state[0] = rotl(s0, 55) ^ s1 ^ (s1 << 14);
            state[1] = rotl(s1, 36);
    
            return result;
    }

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