[thin] Adopt stateful random number generators

base/io_generator.cc

@@ -1,5 +1,7 @@
 #include "base/io_generator.h"
 #include "base/sequence_generator.h"
+#include <chrono>
+#include <random>
 #include <stdexcept>
 #include <cstdlib>
 #include <cstring>
@@ -31,19 +33,23 @@ namespace {
 		typedef std::shared_ptr<op_generator> ptr;
 
 		op_generator(base::req_op op1)
-			: op1_(op1), op2_(op1), op1_pct_(100) {
+			: op1_(op1), op2_(op1), op1_pct_(100),
+			  rand_seed_(std::chrono::high_resolution_clock::now().time_since_epoch().count()),
+			  op_engine_(rand_seed_) {
 		}
 
 		op_generator(base::req_op op1,
 			     base::req_op op2,
 			     unsigned op1_pct)
-			: op1_(op1), op2_(op2), op1_pct_(op1_pct) {
+			: op1_(op1), op2_(op2), op1_pct_(op1_pct),
+			  rand_seed_(std::chrono::high_resolution_clock::now().time_since_epoch().count()),
+			  op_engine_(rand_seed_) {
 			if (op1_pct > 100)
 				throw std::runtime_error("invalid percentage");
 		}
 
 		base::req_op next_op() {
-			if (static_cast<unsigned>(std::rand()) % 100 > op1_pct_)
+			if (op_engine_() % 100 > op1_pct_)
 				return op2_;
 			return op1_;
 		}
@@ -52,6 +58,9 @@ namespace {
 		base::req_op op1_;
 		base::req_op op2_;
 		unsigned op1_pct_;
+		uint64_t rand_seed_;
+
+		std::mt19937 op_engine_;
 	};
 
 	//--------------------------------

base/sequence_generator.cc

@@ -1,5 +1,7 @@
 #include "base/run_set.h"
 #include "base/sequence_generator.h"
+#include <chrono>
+#include <random>
 #include <stdexcept>
 
 //----------------------------------------------------------------
@@ -80,6 +82,9 @@ namespace {
 			: begin_(begin),
 			  step_(step),
 			  max_forward_steps_(seq_nr),
+			  rand_seed_(std::chrono::high_resolution_clock::now().time_since_epoch().count()),
+			  results_engine_(rand_seed_),
+			  steps_engine_(rand_seed_),
 			  nr_generated_(0)
 		{
 			if (!size || !step || !seq_nr)
@@ -93,9 +98,15 @@ namespace {
 			if (!max_forward_steps_ || max_forward_steps_ > nr_steps_)
 				throw std::runtime_error("invalid number of forward steps");
 
-			if (max_forward_steps_ > 1)
+			results_distr_ = std::uniform_int_distribution<uint64_t>(0,
+					nr_steps_ - 1);
+
+			if (max_forward_steps_ > 1) {
+				steps_distr_ = std::uniform_int_distribution<uint64_t>(1,
+						max_forward_steps_);
 				reset_forward_generator();
 			}
+		}
 
 		uint64_t next() {
 			// FIXME: eliminate if-else
@@ -109,7 +120,7 @@ namespace {
 		void reset_forward_generator() {
 			uint64_t begin = peek_random_step();
 
-			unsigned seq_nr = (std::rand() % max_forward_steps_) + 1;
+			unsigned seq_nr = steps_distr_(steps_engine_);
 			base::run_set<uint64_t>::const_iterator it = rand_map_.upper_bound(begin);
 			if (it != rand_map_.end())
 				seq_nr = std::min<uint64_t>(seq_nr, *it->begin_ - begin);
@@ -148,12 +159,13 @@ namespace {
 			}
 		}
 
-		uint64_t peek_random_step() const {
+		// TODO: improve the complexity of generating unique sequence
+		uint64_t peek_random_step() {
 			uint64_t step_idx;
 
 			bool found = true;
 			while (found) {
-				step_idx = std::rand() % nr_steps_;
+				step_idx = results_distr_(results_engine_);
 				found = rand_map_.member(step_idx);
 			}
 
@@ -164,7 +176,12 @@ namespace {
 		uint64_t nr_steps_;
 		uint64_t step_;
 		unsigned max_forward_steps_;
+		uint64_t rand_seed_;
 
+		std::mt19937_64 results_engine_;
+		std::mt19937_64 steps_engine_;
+		std::uniform_int_distribution<uint64_t> results_distr_;
+		std::uniform_int_distribution<uint64_t> steps_distr_;
 		base::run_set<uint64_t> rand_map_;
 		uint64_t nr_generated_;
 		forward_sequence_generator forward_gen_;

thin-provisioning/damage_generator.cc

@@ -1,3 +1,5 @@
+#include <chrono>
+#include <random>
 #include "damage_generator.h"
 
 using namespace thin_provisioning;
@@ -13,12 +15,14 @@ namespace {
 		base::run_set<block_address> visited;
 		block_address nr_visited = 0;
 
-		srand(time(NULL));
+		uint64_t rand_seed(std::chrono::high_resolution_clock::now().time_since_epoch().count());
+		std::mt19937 rand_engine(rand_seed);
+
 		while (nr_blocks) {
 			if (nr_visited == sm_size)
 				break;
 
-			block_address b = rand() % sm_size;
+			block_address b = rand_engine() % sm_size;
 			if (visited.member(b))
 				continue;