From: Artem Zhmurov <zhmurov@gmail.com>
Date: Fri, 9 Oct 2020 15:08:45 +0000 (+0000)
Subject: Cool quote picking can freeze when hardware random number generation is not working
X-Git-Url: http://biod.pnpi.spb.ru/gitweb/?a=commitdiff_plain;h=3491843372177f70cdecdaee206674978479a198;p=alexxy%2Fgromacs.git

Cool quote picking can freeze when hardware random number generation is not working

The bug with hardware random number generation can cause picking of cool quotes to
freeze in an infinite loop on some Ryzen systems. This patch checks the system for
the bug and falls back to PRNGs.
---

diff --git a/src/gromacs/utility/coolstuff.cpp b/src/gromacs/utility/coolstuff.cpp
index 3f42a264f0..55c80cd1cd 100644
--- a/src/gromacs/utility/coolstuff.cpp
+++ b/src/gromacs/utility/coolstuff.cpp
@@ -74,9 +74,9 @@ bool beCool()
 
 //! Return a valid random index into \c arrayRef
 template<typename T>
-const T& getRandomElement(gmx::ArrayRef<const T> arrayRef)
+const T& getPseudoRandomElement(gmx::ArrayRef<const T> arrayRef)
 {
-    std::random_device                    generator;
+    std::mt19937_64                       generator;
     std::uniform_int_distribution<size_t> distribution(0, arrayRef.size() - 1);
     return arrayRef[distribution(generator)];
 }
@@ -116,7 +116,7 @@ std::string bromacs()
 
     if (beCool())
     {
-        return getRandomElement<const char*>(bromacsArray);
+        return getPseudoRandomElement<const char*>(bromacsArray);
     }
     else
     {
@@ -1586,7 +1586,7 @@ std::string getCoolQuote()
 
     if (beCool())
     {
-        auto quote = getRandomElement<Quote>(quoteArray);
+        auto quote = getPseudoRandomElement<Quote>(quoteArray);
         return formatString("GROMACS reminds you: \"%s\" (%s)", quote.text, quote.author);
     }
     else