base: Use the global Mersenne twister throughout

This patch tidies up random number generation to ensure that it is
done consistently throughout the code base. In essence this involves a
clean-up of Ruby, and some code simplifications in the traffic
generator.

As part of this patch a bunch of skewed distributions (off-by-one etc)
have been fixed.

Note that a single global random number generator is used, and that
the object instantiation order will impact the behaviour (the sequence
of numbers will be unaffected, but if module A calles random before
module B then they would obviously see a different outcome). The
dependency on the instantiation order is true in any case due to the
execution-model of gem5, so we leave it as is. Also note that the
global ranom generator is not thread safe at this point.

Regressions using the memtest, TrafficGen or any Ruby tester are
affected and will be updated accordingly.

2 files changed, 8 insertions, 9 deletions

diff --git a/src/cpu/testers/traffic_gen/generators.cc b/src/cpu/testers/traffic_gen/generators.cc
index 7c6bab92c..135765fce 100644
--- a/src/cpu/testers/traffic_gen/generators.cc
+++ b/src/cpu/testers/traffic_gen/generators.cc
@@ -84,7 +84,7 @@ LinearGen::getNextPacket()
 {
     // choose if we generate a read or a write here
     bool isRead = readPercent != 0 &&
-        (readPercent == 100 || random_mt.random<uint8_t>(0, 100) < readPercent);
+        (readPercent == 100 || random_mt.random(0, 100) < readPercent);
 
     assert((readPercent == 0 && !isRead) || (readPercent == 100 && isRead) ||
            readPercent != 100);
@@ -124,7 +124,7 @@ LinearGen::nextPacketTick(bool elastic, Tick delay) const
         return MaxTick;
     } else {
         // return the time when the next request should take place
-        Tick wait = random_mt.random<Tick>(minPeriod, maxPeriod);
+        Tick wait = random_mt.random(minPeriod, maxPeriod);
 
         // compensate for the delay experienced to not be elastic, by
         // default the value we generate is from the time we are
@@ -152,13 +152,13 @@ RandomGen::getNextPacket()
 {
     // choose if we generate a read or a write here
     bool isRead = readPercent != 0 &&
-        (readPercent == 100 || random_mt.random<uint8_t>(0, 100) < readPercent);
+        (readPercent == 100 || random_mt.random(0, 100) < readPercent);
 
     assert((readPercent == 0 && !isRead) || (readPercent == 100 && isRead) ||
            readPercent != 100);
 
     // address of the request
-    Addr addr = random_mt.random<Addr>(startAddr, endAddr - 1);
+    Addr addr = random_mt.random(startAddr, endAddr - 1);
 
     // round down to start address of block
     addr -= addr % blocksize;
@@ -184,15 +184,14 @@ DramGen::getNextPacket()
 
         // choose if we generate a read or a write here
         isRead = readPercent != 0 &&
-            (readPercent == 100 ||
-             random_mt.random<uint8_t>(0, 100) < readPercent);
+            (readPercent == 100 || random_mt.random(0, 100) < readPercent);
 
         assert((readPercent == 0 && !isRead) ||
                (readPercent == 100 && isRead) ||
                readPercent != 100);
 
         // start by picking a random address in the range
-        addr = random_mt.random<Addr>(startAddr, endAddr - 1);
+        addr = random_mt.random(startAddr, endAddr - 1);
 
         // round down to start address of a block, i.e. a DRAM burst
         addr -= addr % blocksize;
@@ -275,7 +274,7 @@ RandomGen::nextPacketTick(bool elastic, Tick delay) const
         return MaxTick;
     } else {
         // return the time when the next request should take place
-        Tick wait = random_mt.random<Tick>(minPeriod, maxPeriod);
+        Tick wait = random_mt.random(minPeriod, maxPeriod);
 
         // compensate for the delay experienced to not be elastic, by
         // default the value we generate is from the time we are
diff --git a/src/cpu/testers/traffic_gen/traffic_gen.cc b/src/cpu/testers/traffic_gen/traffic_gen.cc
index c1ce0d6d4..cbff712bc 100644
--- a/src/cpu/testers/traffic_gen/traffic_gen.cc
+++ b/src/cpu/testers/traffic_gen/traffic_gen.cc
@@ -423,7 +423,7 @@ TrafficGen::transition()
     states[currState]->exit();
 
     // determine next state
-    double p = random_mt.gen_real1();
+    double p = random_mt.random<double>();
     assert(currState < transitionMatrix.size());
     double cumulative = 0.0;
     size_t i = 0;