From e9a9dddd8628435fc7af886c76cd11016ff40d66 Mon Sep 17 00:00:00 2001
From: Rye Mutt <rye@alchemyviewer.org>
Date: Tue, 31 Jan 2023 19:31:00 -0500
Subject: [PATCH] Replace boost random with std random that doesn't break
particles this time
---
indra/llcommon/llrand.cpp | 90 +++++++++++++++++++++++++++------------
1 file changed, 63 insertions(+), 27 deletions(-)
diff --git a/indra/llcommon/llrand.cpp b/indra/llcommon/llrand.cpp
index 5c451b63d0a..b63eed50b02 100644
--- a/indra/llcommon/llrand.cpp
+++ b/indra/llcommon/llrand.cpp
@@ -29,68 +29,104 @@
#include "llrand.h"
#include "lluuid.h"
-#include <boost/random/lagged_fibonacci.hpp>
+#include <random>
-static boost::lagged_fibonacci2281 gRandomGenerator(LLUUID::getRandomSeed());
-inline F64 ll_internal_random_double()
-{
- F64 rv = gRandomGenerator();
- if(!((rv >= 0.0) && (rv < 1.0))) return fmod(rv, 1.0);
- return rv;
-}
+/**
+ * Through analysis, we have decided that we want to take values which
+ * are close enough to 1.0 to map back to 0.0. We came to this
+ * conclusion from noting that:
+ *
+ * [0.0, 1.0)
+ *
+ * when scaled to the integer set:
+ *
+ * [0, 4)
+ *
+ * there is some value close enough to 1.0 that when multiplying by 4,
+ * gets truncated to 4. Therefore:
+ *
+ * [0,1-eps] => 0
+ * [1,2-eps] => 1
+ * [2,3-eps] => 2
+ * [3,4-eps] => 3
+ *
+ * So 0 gets uneven distribution if we simply clamp. The actual
+ * clamp utilized in this file is to map values out of range back
+ * to 0 to restore uniform distribution.
+ *
+ * Also, for clamping floats when asking for a distribution from
+ * [0.0,g) we have determined that for values of g < 0.5, then
+ * rand*g=g, which is not the desired result. As above, we clamp to 0
+ * to restore uniform distribution.
+ */
-inline F32 ll_internal_random_float()
+static thread_local std::unique_ptr<std::ranlux48> __generator;
+inline std::ranlux48* _generator()
{
- // The clamping rules are described above.
- F32 rv = (F32)gRandomGenerator();
- if(!((rv >= 0.0f) && (rv < 1.0f))) return fmod(rv, 1.f);
- return rv;
+ if (!__generator.get())
+ {
+ std::random_device seeder;
+ __generator = std::make_unique<std::ranlux48>(seeder());
+ }
+ return __generator.get();
}
S32 ll_rand()
{
- return ll_rand(RAND_MAX);
+ return ll_rand(S32_MAX);
}
S32 ll_rand(S32 val)
{
- S32 rv = (S32)(ll_internal_random_double() * val);
- if(rv == val) return 0;
+ if (val == 0) return 0;
+
+ // The clamping rules are described above.
+ S32 rv;
+ if (val > 0)
+ {
+ rv = std::uniform_int_distribution<S32>(0, val)(*_generator());
+ }
+ else
+ {
+ rv = std::uniform_int_distribution<S32>(val, 0)(*_generator());
+ }
+ if (rv == val) return 0;
return rv;
}
F32 ll_frand()
{
- return ll_internal_random_float();
+ // see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63176
+ // and https://llvm.org/bugs/show_bug.cgi?id=18767
+ // and https://github.com/microsoft/STL/issues/1074
+ return (F32)std::generate_canonical<F64, 10>((*_generator()));
}
F32 ll_frand(F32 val)
{
- // The clamping rules are described above.
- F32 rv = ll_internal_random_float() * val;
- if(val > 0)
+ F32 rv = ll_frand() * val;
+ if (val > 0.0f)
{
- if(rv >= val) return 0.0f;
+ if (rv >= val) return 0.0f;
}
else
{
- if(rv <= val) return 0.0f;
+ if (rv <= val) return 0.0f;
}
return rv;
}
F64 ll_drand()
{
- return ll_internal_random_double();
+ return std::generate_canonical<F64, 10>((*_generator()));
}
F64 ll_drand(F64 val)
{
- // The clamping rules are described above.
- F64 rv = ll_internal_random_double() * val;
- if(val > 0)
+ F64 rv = ll_drand() * val;
+ if (val > 0.0)
{
- if(rv >= val) return 0.0;
+ if (rv >= val) return 0.0;
}
else
{
--
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