From f0806d5d7c1eb4f9e4abc82150c5aa3e0e25e713 Mon Sep 17 00:00:00 2001
From: Mark Olesen <Mark.Olesen@esi-group.com>
Date: Wed, 13 Jun 2018 12:38:13 +0200
Subject: [PATCH] BUG: non-uniform distribution for Random::position<label>
(closes #865)
- use floor/truncate instead of round. Backport of changes in the
develop-pre-release branch.
---
.../primitives/random/Random/Random.C | 27 +++++++++++++++----
1 file changed, 22 insertions(+), 5 deletions(-)
diff --git a/src/OpenFOAM/primitives/random/Random/Random.C b/src/OpenFOAM/primitives/random/Random/Random.C
index c17f5c26689..13073f586e3 100644
--- a/src/OpenFOAM/primitives/random/Random/Random.C
+++ b/src/OpenFOAM/primitives/random/Random/Random.C
@@ -151,7 +151,24 @@ Foam::scalar Foam::Random::position
template<>
Foam::label Foam::Random::position(const label& start, const label& end)
{
- return start + round(scalar01()*(end - start));
+ #ifdef FULLDEBUG
+ if (start > end)
+ {
+ FatalErrorInFunction
+ << "start index " << start << " > end index " << end << nl
+ << abort(FatalError);
+ }
+ #endif
+
+ // Extend the upper sampling range by 1 and floor the result.
+ // Since the range is non-negative, can use integer truncation
+ // instead using floor().
+
+ const label val = start + label(scalar01()*(end - start + 1));
+
+ // Rare case when scalar01() returns exactly 1.000 and the truncated
+ // value would be out of range.
+ return min(val, end);
}
@@ -230,12 +247,12 @@ Foam::scalar Foam::Random::globalPosition
if (Pstream::master())
{
- value = scalar01()*(end - start);
+ value = position<scalar>(start, end);
}
Pstream::scatter(value);
- return start + value;
+ return value;
}
@@ -250,12 +267,12 @@ Foam::label Foam::Random::globalPosition
if (Pstream::master())
{
- value = round(scalar01()*(end - start));
+ value = position<label>(start, end);
}
Pstream::scatter(value);
- return start + value;
+ return value;
}
--
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