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.

7 files changed, 38 insertions, 32 deletions

diff --git a/src/cpu/testers/directedtest/SeriesRequestGenerator.cc b/src/cpu/testers/directedtest/SeriesRequestGenerator.cc
index f4bb578e3..80523280b 100644
--- a/src/cpu/testers/directedtest/SeriesRequestGenerator.cc
+++ b/src/cpu/testers/directedtest/SeriesRequestGenerator.cc
@@ -27,6 +27,7 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+#include "base/random.hh"
 #include "cpu/testers/directedtest/DirectedGenerator.hh"
 #include "cpu/testers/directedtest/RubyDirectedTester.hh"
 #include "cpu/testers/directedtest/SeriesRequestGenerator.hh"
@@ -60,7 +61,7 @@ SeriesRequestGenerator::initiate()
     Request *req = new Request(m_address, 1, flags, masterId);
 
     Packet::Command cmd;
-    bool do_write = ((random() % 100) < m_percent_writes);
+    bool do_write = (random_mt.random(0, 100) < m_percent_writes);
     if (do_write) {
         cmd = MemCmd::WriteReq;
     } else {
diff --git a/src/cpu/testers/memtest/memtest.cc b/src/cpu/testers/memtest/memtest.cc
index 7f3ff0d03..6dc2ccb73 100644
--- a/src/cpu/testers/memtest/memtest.cc
+++ b/src/cpu/testers/memtest/memtest.cc
@@ -37,6 +37,7 @@
 #include <vector>
 
 #include "base/misc.hh"
+#include "base/random.hh"
 #include "base/statistics.hh"
 #include "cpu/testers/memtest/memtest.hh"
 #include "debug/MemTest.hh"
@@ -261,14 +262,14 @@ MemTest::tick()
     }
 
     //make new request
-    unsigned cmd = random() % 100;
-    unsigned offset = random() % size;
-    unsigned base = random() % 2;
-    uint64_t data = random();
-    unsigned access_size = random() % 4;
-    bool uncacheable = (random() % 100) < percentUncacheable;
+    unsigned cmd = random_mt.random(0, 100);
+    unsigned offset = random_mt.random<unsigned>(0, size - 1);
+    unsigned base = random_mt.random(0, 1);
+    uint64_t data = random_mt.random<uint64_t>();
+    unsigned access_size = random_mt.random(0, 3);
+    bool uncacheable = random_mt.random(0, 100) < percentUncacheable;
 
-    unsigned dma_access_size = random() % 4; 
+    unsigned dma_access_size = random_mt.random(0, 3);
 
     //If we aren't doing copies, use id as offset, and do a false sharing
     //mem tester
@@ -296,7 +297,8 @@ MemTest::tick()
         return;
     }
 
-    bool do_functional = (random() % 100 < percentFunctional) && !uncacheable;
+    bool do_functional = (random_mt.random(0, 100) < percentFunctional) &&
+        !uncacheable;
     Request *req = new Request();
     uint8_t *result = new uint8_t[8];
 
diff --git a/src/cpu/testers/networktest/networktest.cc b/src/cpu/testers/networktest/networktest.cc
index 8fff53aa7..c2d34489b 100644
--- a/src/cpu/testers/networktest/networktest.cc
+++ b/src/cpu/testers/networktest/networktest.cc
@@ -35,6 +35,7 @@
 #include <vector>
 
 #include "base/misc.hh"
+#include "base/random.hh"
 #include "base/statistics.hh"
 #include "cpu/testers/networktest/networktest.hh"
 #include "debug/NetworkTest.hh"
@@ -143,7 +144,7 @@ NetworkTest::tick()
     // - send pkt if this number is < injRate*(10^precision)
     bool send_this_cycle;
     double injRange = pow((double) 10, (double) precision);
-    unsigned trySending = random() % (int) injRange;
+    unsigned trySending = random_mt.random<unsigned>(0, (int) injRange);
     if (trySending < injRate*injRange)
         send_this_cycle = true;
     else
@@ -174,7 +175,7 @@ NetworkTest::generatePkt()
 {
     unsigned destination = id;
     if (trafficType == 0) { // Uniform Random
-        destination = random() % numMemories;
+        destination = random_mt.random<unsigned>(0, numMemories - 1);
     } else if (trafficType == 1) { // Tornado
         int networkDimension = (int) sqrt(numMemories);
         int my_x = id%networkDimension;
@@ -232,7 +233,7 @@ NetworkTest::generatePkt()
     // 
     MemCmd::Command requestType;
 
-    unsigned randomReqType = random() % 3;
+    unsigned randomReqType = random_mt.random(0, 2);
     if (randomReqType == 0) {
         // generate packet for virtual network 0
         requestType = MemCmd::ReadReq;
diff --git a/src/cpu/testers/rubytest/Check.cc b/src/cpu/testers/rubytest/Check.cc
index b2b679018..126deba6d 100644
--- a/src/cpu/testers/rubytest/Check.cc
+++ b/src/cpu/testers/rubytest/Check.cc
@@ -27,6 +27,7 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+#include "base/random.hh"
 #include "cpu/testers/rubytest/Check.hh"
 #include "debug/RubyTest.hh"
 #include "mem/ruby/common/SubBlock.hh"
@@ -46,7 +47,8 @@ Check::Check(const Address& address, const Address& pc,
     pickInitiatingNode();
     changeAddress(address);
     m_pc = pc;
-    m_access_mode = RubyAccessMode(random() % RubyAccessMode_NUM);
+    m_access_mode = RubyAccessMode(random_mt.random(0,
+                                                    RubyAccessMode_NUM - 1));
     m_store_count = 0;
 }
 
@@ -57,11 +59,11 @@ Check::initiate()
     debugPrint();
 
     // currently no protocols support prefetches
-    if (false && (random() & 0xf) == 0) {
+    if (false && (random_mt.random(0, 0xf) == 0)) {
         initiatePrefetch(); // Prefetch from random processor
     }
 
-    if (m_tester_ptr->getCheckFlush() && (random() & 0xff) == 0) {
+        if (m_tester_ptr->getCheckFlush() && (random_mt.random(0, 0xff) == 0)) {
         initiateFlush(); // issue a Flush request from random processor
     }
 
@@ -81,7 +83,7 @@ Check::initiatePrefetch()
 {
     DPRINTF(RubyTest, "initiating prefetch\n");
 
-    int index = random() % m_num_readers;
+    int index = random_mt.random(0, m_num_readers - 1);
     MasterPort* port = m_tester_ptr->getReadableCpuPort(index);
 
     Request::Flags flags;
@@ -90,7 +92,7 @@ Check::initiatePrefetch()
     Packet::Command cmd;
 
     // 1 in 8 chance this will be an exclusive prefetch
-    if ((random() & 0x7) != 0) {
+    if (random_mt.random(0, 0x7) != 0) {
         cmd = MemCmd::ReadReq;
 
         // if necessary, make the request an instruction fetch
@@ -132,7 +134,7 @@ Check::initiateFlush()
 
     DPRINTF(RubyTest, "initiating Flush\n");
 
-    int index = random() % m_num_writers;
+    int index = random_mt.random(0, m_num_writers - 1);
     MasterPort* port = m_tester_ptr->getWritableCpuPort(index);
 
     Request::Flags flags;
@@ -161,7 +163,7 @@ Check::initiateAction()
     DPRINTF(RubyTest, "initiating Action\n");
     assert(m_status == TesterStatus_Idle);
 
-    int index = random() % m_num_writers;
+    int index = random_mt.random(0, m_num_writers - 1);
     MasterPort* port = m_tester_ptr->getWritableCpuPort(index);
 
     Request::Flags flags;
@@ -222,7 +224,7 @@ Check::initiateCheck()
     DPRINTF(RubyTest, "Initiating Check\n");
     assert(m_status == TesterStatus_Ready);
 
-    int index = random() % m_num_readers;
+    int index = random_mt.random(0, m_num_readers - 1);
     MasterPort* port = m_tester_ptr->getReadableCpuPort(index);
 
     Request::Flags flags;
@@ -339,7 +341,7 @@ Check::pickValue()
 {
     assert(m_status == TesterStatus_Idle);
     m_status = TesterStatus_Idle;
-    m_value = random() & 0xff; // One byte
+    m_value = random_mt.random(0, 0xff); // One byte
     m_store_count = 0;
 }
 
@@ -348,7 +350,7 @@ Check::pickInitiatingNode()
 {
     assert(m_status == TesterStatus_Idle || m_status == TesterStatus_Ready);
     m_status = TesterStatus_Idle;
-    m_initiatingNode = (random() % m_num_writers);
+    m_initiatingNode = (random_mt.random(0, m_num_writers - 1));
     DPRINTF(RubyTest, "picked initiating node %d\n", m_initiatingNode);
     m_store_count = 0;
 }
diff --git a/src/cpu/testers/rubytest/CheckTable.cc b/src/cpu/testers/rubytest/CheckTable.cc
index f10132c89..df2bf864d 100644
--- a/src/cpu/testers/rubytest/CheckTable.cc
+++ b/src/cpu/testers/rubytest/CheckTable.cc
@@ -28,6 +28,7 @@
  */
 
 #include "base/intmath.hh"
+#include "base/random.hh"
 #include "cpu/testers/rubytest/Check.hh"
 #include "cpu/testers/rubytest/CheckTable.hh"
 #include "debug/RubyTest.hh"
@@ -107,7 +108,7 @@ Check*
 CheckTable::getRandomCheck()
 {
     assert(m_check_vector.size() > 0);
-    return m_check_vector[random() % m_check_vector.size()];
+    return m_check_vector[random_mt.random<unsigned>(0, m_check_vector.size() - 1)];
 }
 
 Check*
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;