Update xoroshiro128+ to 1.0 version

README.txt

@@ -25,13 +25,17 @@ NOTE: This library is not designed for cryptographic applications
   ------------------
 
 Xoroshiro128+ is an RNG algorithm developed in 2016 by David Blackman
-and Sebastiano Vigna. It is a further development of the Xorshift algorithm
-invented by George Marsaglia
+and Sebastiano Vigna. The VHDL code matches an updated version of
+the algorithm called "xoroshiro128+ 1.0", released in 2018.
+The Xoroshiro algorithm is based on the Xorshift concept invented
+by George Marsaglia.
 
-See also http://xoroshiro.di.unimi.it/
+See also http://prng.di.unimi.it/
 
-This RNG passes many statistical tests. Its period, 2**128 - 1, is long
-compared to a typical LFSR, but much shorter than the Mersenne Twister.
+This RNG passes many statistical tests, but the least significant
+output bits are known to be not fully random and fail certain tests.
+The generator has a long period (2**128 - 1) compared to a typical LFSR,
+but much shorter than the Mersenne Twister.
 The output is 1-dimensionally equidistributed.
 
 The VHDL implementation produces 64 new random bits on every (enabled)
@@ -43,7 +47,7 @@ Seed length:        128 bits
 Period:             2**128 - 1
 
 FPGA resources:     general logic and 64-bit adder
-Synthesis results:  194 LUTs, 192 registers on Spartan-6
+Synthesis results:  198 LUTs, 193 registers on Spartan-6
 Timing results:     333 MHz on Spartan-6 LX45-3
 
 
@@ -141,7 +145,7 @@ Timing results:     380 MHz on Spartan-6 LX45-3 (32 bits output)
   License
   -------
 
-Copyright (C) 2016 Joris van Rantwijk
+Copyright (C) 2016-2020 Joris van Rantwijk
 
 This VHDL library is free software; you can redistribute it and/or
 modify it under the terms of the GNU Lesser General Public License

refimpl/Makefile

@@ -10,9 +10,9 @@ CFLAGS = -std=c11 -Wall -O2
 CXXFLAGS = -std=c++11 -Wall -O2
 
 .PHONY: all
-all: ref_xoroshiro ref_mt19937 ref_trivium
+all: ref_xoroshiro128plus ref_mt19937 ref_trivium
 
-ref_xoroshiro: ref_xoroshiro.c
+ref_xoroshiro128plus: ref_xoroshiro128plus.c
 
 ref_mt19937: ref_mt19937.cpp
 
@@ -20,5 +20,5 @@ ref_trivium: ref_trivium.cpp
 
 .PHONY: clean
 clean:
-	$(RM) ref_xoroshiro ref_mt19937 ref_trivium
+	$(RM) ref_xoroshiro128plus ref_mt19937 ref_trivium
 

refimpl/ref_xoroshiro128plus.c

@@ -13,14 +13,13 @@
 
 #include <stdlib.h>
 #include <stdio.h>
-#include <stdint.h>
 
 
 /*  ========== BEGIN of reference implementation of xoroshiro128+ ==========
- *  Source: http://xoroshiro.di.unimi.it/
+ *  Source: http://prng.di.unimi.it/
  */
 
-/*  Written in 2016 by David Blackman and Sebastiano Vigna (vigna@acm.org)
+/*  Written in 2016-2018 by David Blackman and Sebastiano Vigna (vigna@acm.org)
 
 To the extent possible under law, the author has dedicated all copyright
 and related and neighboring rights to this software to the public domain
@@ -28,20 +27,46 @@ worldwide. This software is distributed without any warranty.
 
 See <http://creativecommons.org/publicdomain/zero/1.0/>. */
 
-int64_t s[2];
+#include <stdint.h>
+
+/* This is xoroshiro128+ 1.0, our best and fastest small-state generator
+   for floating-point numbers. We suggest to use its upper bits for
+   floating-point generation, as it is slightly faster than
+   xoroshiro128++/xoroshiro128**. It passes all tests we are aware of
+   except for the four lower bits, which might fail linearity tests (and
+   just those), so if low linear complexity is not considered an issue (as
+   it is usually the case) it can be used to generate 64-bit outputs, too;
+   moreover, this generator has a very mild Hamming-weight dependency
+   making our test (http://prng.di.unimi.it/hwd.php) fail after 5 TB of
+   output; we believe this slight bias cannot affect any application. If
+   you are concerned, use xoroshiro128++, xoroshiro128** or xoshiro256+.
+
+   We suggest to use a sign test to extract a random Boolean value, and
+   right shifts to extract subsets of bits.
+
+   The state must be seeded so that it is not everywhere zero. If you have
+   a 64-bit seed, we suggest to seed a splitmix64 generator and use its
+   output to fill s. 
+
+   NOTE: the parameters (a=24, b=16, b=37) of this version give slightly
+   better results in our test than the 2016 version (a=55, b=14, c=36).
+*/
 
 static inline uint64_t rotl(const uint64_t x, int k) {
 	return (x << k) | (x >> (64 - k));
 }
 
+
+static uint64_t s[2];
+
 uint64_t next(void) {
 	const uint64_t s0 = s[0];
 	uint64_t s1 = s[1];
 	const uint64_t result = s0 + s1;
 
 	s1 ^= s0;
-    s[0] = rotl(s0, 55) ^ s1 ^ (s1 << 14); // a, b
-    s[1] = rotl(s1, 36); // c
+	s[0] = rotl(s0, 24) ^ s1 ^ (s1 << 16); // a, b
+	s[1] = rotl(s1, 37); // c
 
 	return result;
 }
@@ -58,12 +83,12 @@ int main(int argc, const char **argv)
     if (argc != 4) {
         fprintf(stderr, "Reference implementation of RNG xoroshiro128+\n");
         fprintf(stderr, "\n");
-        fprintf(stderr, "Usage: ref_xoroshiro SEED0 SEED1 NUMVALUE\n");
+        fprintf(stderr, "Usage: ref_xoroshiro128plus SEED0 SEED1 NUMVALUE\n");
         fprintf(stderr, "    SEED0     seed value in range 0 .. (2**64-1)\n");
         fprintf(stderr, "    SEED1     seed value in range 0 .. (2**64-1)\n");
         fprintf(stderr, "    NUMVALUE  number of values to get from generator\n");
         fprintf(stderr, "\n");
-        fprintf(stderr, "Example: ref_xoroshiro 0x3141592653589793 "
+        fprintf(stderr, "Example: ref_xoroshiro128plus 0x3141592653589793 "
                         "0x0123456789abcdef 100\n");
         exit(1);
     }

rtl/rng_xoroshiro128plus.vhdl

@@ -1,5 +1,5 @@
 --
---  Pseudo Random Number Generator "xoroshiro128+".
+--  Pseudo Random Number Generator "xoroshiro128+ 1.0".
 --
 --  Author: Joris van Rantwijk <joris@jorisvr.nl>
 --
@@ -7,9 +7,9 @@
 --  The generator can produce 64 new random bits on every clock cycle.
 --
 --  The algorithm "xoroshiro128+" is by David Blackman and Sebastiano Vigna.
---  See also http://xoroshiro.di.unimi.it/
+--  See also http://prng.di.unimi.it/
 --
---  The generator requires a 128-bit seed value, not equal to zero.
+--  The generator requires a 128-bit seed value, not equal to all zeros.
 --  A default seed must be supplied at compile time and will be used
 --  to initialize the generator at reset. The generator also supports
 --  re-seeding at run time.
@@ -19,12 +19,12 @@
 --
 --  NOTE: This is not a cryptographic random number generator.
 --
---  NOTE: The least significant output bit is less random than
---        all other output bits.
+--  NOTE: The least significant output bits are not fully random and
+--        fail certain statistical tests.
 --
 
 --
---  Copyright (C) 2016 Joris van Rantwijk
+--  Copyright (C) 2016-2020 Joris van Rantwijk
 --
 --  This code is free software; you can redistribute it and/or
 --  modify it under the terms of the GNU Lesser General Public
@@ -131,12 +131,12 @@ begin
                 -- Update internal state.
                 reg_state_s0    <= reg_state_s0 xor
                                    reg_state_s1 xor
-                                   shiftl(reg_state_s0, 14) xor
-                                   shiftl(reg_state_s1, 14) xor
-                                   rotl(reg_state_s0, 55);
+                                   rotl(reg_state_s0, 24) xor
+                                   shiftl(reg_state_s0, 16) xor
+                                   shiftl(reg_state_s1, 16);
 
-                reg_state_s1    <= rotl(reg_state_s0, 36) xor
-                                   rotl(reg_state_s1, 36);
+                reg_state_s1    <= rotl(reg_state_s0, 37) xor
+                                   rotl(reg_state_s1, 37);
 
             end if;