From e582b80c900f66fefcd97b70425cce2222857979 Mon Sep 17 00:00:00 2001
From: Ivan Smirnov <ifsmirnov@yandex.ru>
Date: Tue, 6 Feb 2018 20:24:49 +0300
Subject: [PATCH] Use several random_device calls to initialize rnd

---
 doc/random.md | 4 ++--
 jngen.h       | 9 ++++++++-
 random.h      | 9 ++++++++-
 3 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/doc/random.md b/doc/random.md
index ba1bfda..b157abc 100644
--- a/doc/random.md
+++ b/doc/random.md
@@ -1,6 +1,6 @@
 ## Random numbers generation
 
-Jngen provides a class *Random* whose behavior is similar to *rnd* from testlib.h. E.g. you may write *rnd.next(100)*, *rnd.next("[a-z]{%d}, n)*, and so on.  Most of interaction with *Random* happens via its global instance of *Random* called *rnd*.
+Jngen provides a class *Random* whose behavior is similar to *rnd* from testlib.h. E.g. you may write *rnd.next(100)*, *rnd.next("[a-z]{%d}", n)*, and so on.  Most of interaction with *Random* happens via its global instance of *Random* called *rnd*.
 
 Default initialized *Random* is seeded with some hardware-generated random value, so subsequent executions of the program will produce different tests. This may be useful for local stress-testing, for example. If you want to fix the seed, use *registerGen(argc, argv)* at the beginning of your *main*.
 
@@ -17,7 +17,7 @@ Default initialized *Random* is seeded with some hardware-generated random value
 #### int next(int l, int r) // also for long long, size\_t, double
 * Returns: random integer in range [l, r].
 #### int wnext(int n, int w) // also for long long, size\_t, double
-* If w > 0, returns max(next(n), ..., next(n)) (w times). If w < 0, returns min(next(n), ..., next(n)) (-w times). If w = 0, same as next(n).
+* If w > 0, returns max(next(n), ..., next(n)) (w times). If w &lt; 0, returns min(next(n), ..., next(n)) (-w times). If w = 0, same as next(n).
 #### int wnext(int l, int r, int w) // also for long long, size\_t, double
 * Same as wnext(n, w), but the range is [l, r].
 #### std::string next(const std::string& pattern)
diff --git a/jngen.h b/jngen.h
index 65d9ad5..dc3dddb 100644
--- a/jngen.h
+++ b/jngen.h
@@ -1661,7 +1661,14 @@ class Random {
     Random() {
         assertRandomEngineConsistency();
         assertIntegerSizes();
-        seed(std::random_device{}());
+        std::vector<uint32_t> seedSeq;
+        // 4 random_device calls is enough for everyone
+        std::random_device rd;
+        for (size_t i = 0; i < 4; ++i) {
+            seedSeq.push_back(rd());
+        }
+        seed(seedSeq);
+
     }
 
     void seed(uint32_t val);
diff --git a/random.h b/random.h
index 239f87c..8e741b7 100644
--- a/random.h
+++ b/random.h
@@ -57,7 +57,14 @@ class Random {
     Random() {
         assertRandomEngineConsistency();
         assertIntegerSizes();
-        seed(std::random_device{}());
+        std::vector<uint32_t> seedSeq;
+        // 4 random_device calls is enough for everyone
+        std::random_device rd;
+        for (size_t i = 0; i < 4; ++i) {
+            seedSeq.push_back(rd());
+        }
+        seed(seedSeq);
+
     }
 
     void seed(uint32_t val);