X-Git-Url: https://git.auder.net/?a=blobdiff_plain;f=code%2Fstage1%2Fsrc%2FUtil%2Frng.c;fp=code%2Fstage1%2Fsrc%2FUtil%2Frng.c;h=6cd402521cf2a7d2484a937857426ad64202047f;hb=4b7107ce2a0bb77b5b65a9b0617192b0a07fda29;hp=0000000000000000000000000000000000000000;hpb=311c5c078a9fc8ec6bb449fa685dbb1657d75d39;p=epclust.git

diff --git a/code/stage1/src/Util/rng.c b/code/stage1/src/Util/rng.c
new file mode 100644
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--- /dev/null
+++ b/code/stage1/src/Util/rng.c
@@ -0,0 +1,135 @@
+// ISAAC PRNG
+// Initial code by Bob Jenkins, March 1996 - modified in 2008
+// Reference: http://burtleburtle.net/bob/rand/isaacafa.html
+// Further slightly modified by Benjamin Auder, 2013
+
+#include "Util/rng.h"
+#include <stdlib.h>
+#include <time.h>
+
+// Internal state
+static uint32_t mm[256];
+static uint32_t aa, bb, cc;
+
+// initialize the (pseudo-)random generator
+void init_rng(int flag)
+{
+	// 'bootstrap' isaac with basic bad PRNG
+	srand(time(NULL));
+
+	aa = rand() & 0xffffffff;
+	bb = rand() & 0xffffffff;
+	cc = rand() & 0xffffffff;
+
+	uint32_t a, b, c, d, e, f, g, h, i;
+	// The golden ratio:
+	a = b = c = d = e = f = g = h = 0x9e3779b9;
+	// Scramble it
+	for (i = 0; i < 4; ++i)
+		mix(a, b, c, d, e, f, g, h);
+
+	// Fill in mm[] with messy stuff (the seed)
+	uint32_t seedArray[256];
+	for (i = 0; i < 256; ++i) mm[i] = seedArray[i] = rand() & 0xffffffff;
+	for (i = 0; i < 256; i += 8)
+	{
+		if (flag)
+		{
+			// Use all the information in the seed
+			a += seedArray[i  ];
+			b += seedArray[i + 1];
+			c += seedArray[i + 2];
+			d += seedArray[i + 3];
+			e += seedArray[i + 4];
+			f += seedArray[i + 5];
+			g += seedArray[i + 6];
+			h += seedArray[i + 7];
+		}
+		mix(a, b, c, d, e, f, g, h);
+		mm[i  ] = a;
+		mm[i + 1] = b;
+		mm[i + 2] = c;
+		mm[i + 3] = d;
+		mm[i + 4] = e;
+		mm[i + 5] = f;
+		mm[i + 6] = g;
+		mm[i + 7] = h;
+	}
+
+	if (flag)
+	{
+		// Do a second pass to make all of the seed affect all of mm
+		for (i = 0; i < 256; i += 8)
+		{
+			a += mm[i  ];
+			b += mm[i + 1];
+			c += mm[i + 2];
+			d += mm[i + 3];
+			e += mm[i + 4];
+			f += mm[i + 5];
+			g += mm[i + 6];
+			h += mm[i + 7];
+			mix(a, b, c, d, e, f, g, h);
+			mm[i  ] = a;
+			mm[i + 1] = b;
+			mm[i + 2] = c;
+			mm[i + 3] = d;
+			mm[i + 4] = e;
+			mm[i + 5] = f;
+			mm[i + 6] = g;
+			mm[i + 7] = h;
+		}
+	}
+}
+
+// return a (pseudo-)random integer
+uint32_t get_rand_int()
+{
+	// TODO: register variables ? (x,y,i)
+	uint32_t x, y;
+	static uint32_t i = 0;
+
+	if (i == 0)
+	{
+		cc = cc + 1;  // cc just gets incremented once per 256 results
+		bb = bb + cc; // then combined with bb
+	}
+
+	x = mm[i];
+	switch (i % 4)
+	{
+	case 0:
+		aa = aa^(aa << 13);
+		break;
+	case 1:
+		aa = aa^(aa >> 6);
+		break;
+	case 2:
+		aa = aa^(aa << 2);
+		break;
+	case 3:
+		aa = aa^(aa >> 16);
+		break;
+	}
+
+	// NOTE: bits 2..9 are chosen from x but 10..17 are chosen
+	//       from y.  The only important thing here is that 2..9 and 10..17
+	//       don't overlap.  2..9 and 10..17 were then chosen for speed in
+	//       the optimized version (rand.c) */
+	// See http://burtleburtle.net/bob/rand/isaac.html
+	// for further explanations and analysis.
+
+	aa        = mm[(i + 128) % 256] + aa;
+	mm[i] = y = mm[(x >> 2) % 256]  + aa + bb;
+	bb        = mm[(y >> 10) % 256] + x;
+
+	i = (i + 1) % 256;
+
+	return bb;
+}
+
+// return a (pseudo-)random real number in [0,1]
+Real get_rand_real()
+{
+	return (Real) (INV_RANDMAX * (double) get_rand_int());
+}