X-Git-Url: https://git.kernel.dk/?a=blobdiff_plain;f=lib%2Frand.c;h=3b2d67ad6e9ebc4a242b24c162f94aa667a11743;hb=c44b1ff54402c589e8f07436ec56efb4f8b1ac23;hp=b8d8f78d31fb13893d1ee879f84922ccc28cd5a5;hpb=7e744013dca36be3840c45d13f4ae09947282bea;p=fio.git

diff --git a/lib/rand.c b/lib/rand.c
index b8d8f78d..3b2d67ad 100644
--- a/lib/rand.c
+++ b/lib/rand.c
@@ -1,4 +1,40 @@
+/*
+  This is a maximally equidistributed combined Tausworthe generator
+  based on code from GNU Scientific Library 1.5 (30 Jun 2004)
+
+   x_n = (s1_n ^ s2_n ^ s3_n)
+
+   s1_{n+1} = (((s1_n & 4294967294) <<12) ^ (((s1_n <<13) ^ s1_n) >>19))
+   s2_{n+1} = (((s2_n & 4294967288) << 4) ^ (((s2_n << 2) ^ s2_n) >>25))
+   s3_{n+1} = (((s3_n & 4294967280) <<17) ^ (((s3_n << 3) ^ s3_n) >>11))
+
+   The period of this generator is about 2^88.
+
+   From: P. L'Ecuyer, "Maximally Equidistributed Combined Tausworthe
+   Generators", Mathematics of Computation, 65, 213 (1996), 203--213.
+
+   This is available on the net from L'Ecuyer's home page,
+
+   http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme.ps
+   ftp://ftp.iro.umontreal.ca/pub/simulation/lecuyer/papers/tausme.ps
+
+   There is an erratum in the paper "Tables of Maximally
+   Equidistributed Combined LFSR Generators", Mathematics of
+   Computation, 68, 225 (1999), 261--269:
+   http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme2.ps
+
+        ... the k_j most significant bits of z_j must be non-
+        zero, for each j. (Note: this restriction also applies to the
+        computer code given in [4], but was mistakenly not mentioned in
+        that paper.)
+
+   This affects the seeding procedure by imposing the requirement
+   s1 > 1, s2 > 7, s3 > 15.
+
+*/
+
 #include "rand.h"
+#include "../hash.h"
 
 struct frand_state __fio_rand_state;
 
@@ -7,18 +43,49 @@ static inline int __seed(unsigned int x, unsigned int m)
 	return (x < m) ? x + m : x;
 }
 
+static void __init_rand(struct frand_state *state, unsigned int seed)
+{
+	int cranks = 6;
+
+#define LCG(x, seed)  ((x) * 69069 ^ (seed))
+
+	state->s1 = __seed(LCG((2^31) + (2^17) + (2^7), seed), 1);
+	state->s2 = __seed(LCG(state->s1, seed), 7);
+	state->s3 = __seed(LCG(state->s2, seed), 15);
+
+	while (cranks--)
+		__rand(state);
+}
+
 void init_rand(struct frand_state *state)
 {
-#define LCG(x)  ((x) * 69069)   /* super-duper LCG */
-
-	state->s1 = __seed(LCG((2^31) + (2^17) + (2^7)), 1);
-	state->s2 = __seed(LCG(state->s1), 7);
-	state->s3 = __seed(LCG(state->s2), 15);
-
-	__rand(state);
-	__rand(state);
-	__rand(state);
-	__rand(state);
-	__rand(state);
-	__rand(state);
+	__init_rand(state, 1);
+}
+
+void init_rand_seed(struct frand_state *state, unsigned int seed)
+{
+	__init_rand(state, seed);
+}
+
+void __fill_random_buf(void *buf, unsigned int len, unsigned long seed)
+{
+	long *ptr = buf;
+
+	while ((void *) ptr - buf < len) {
+		*ptr = seed;
+		ptr++;
+		seed *= GOLDEN_RATIO_PRIME;
+		seed >>= 3;
+	}
+}
+
+unsigned long fill_random_buf(void *buf, unsigned int len)
+{
+	unsigned long r = __rand(&__fio_rand_state);
+
+	if (sizeof(int) != sizeof(long *))
+		r *= (unsigned long) __rand(&__fio_rand_state);
+
+	__fill_random_buf(buf, len, r);
+	return r;
 }