Fix definition of InterarrivalTimer to enable late initialization

and use nanoseconds

test/cpp/qps/interarrival.h

@@ -31,8 +31,8 @@
  *
  */
 
-#ifndef TEST_QPS_TIMER_H
-#define TEST_QPS_TIMER_H
+#ifndef TEST_QPS_INTERARRIVAL_H
+#define TEST_QPS_INTERARRIVAL_H
 
 #include <chrono>
 #include <cmath>
@@ -112,11 +112,17 @@ using qps_random_engine = std::default_random_engine;
 
 class InterarrivalTimer {
 public:
+  InterarrivalTimer() {}
   InterarrivalTimer(const RandomDist& r, int threads, int entries=1000000) {
+    init(r, threads, entries);
+  }
+  void init(const RandomDist& r, int threads, int entries=1000000) {
     qps_random_engine gen;
     std::uniform_real_distribution<double> uniform(0.0,1.0);
     for (int i=0; i<entries; i++) {
-      random_table_.push_back(std::chrono::microseconds(static_cast<int64_t>(1000000.0*r(uniform(gen)))));
+      random_table_.push_back(
+          std::chrono::nanoseconds(
+              static_cast<int64_t>(1e9*r(uniform(gen)))));
     }
     // Now set up the thread positions
     for (int i=0; i<threads; i++) {
@@ -125,14 +131,14 @@ public:
   }
   virtual ~InterarrivalTimer() {};
 
-  std::chrono::microseconds operator() (int thread_num) {
+  std::chrono::nanoseconds operator() (int thread_num) {
     auto ret = *(thread_posns_[thread_num]++);
     if (thread_posns_[thread_num] == random_table_.end())
       thread_posns_[thread_num] = random_table_.begin();
     return ret;
   }
  private:
-  typedef std::vector<std::chrono::microseconds> time_table;
+  typedef std::vector<std::chrono::nanoseconds> time_table;
   std::vector<time_table::const_iterator> thread_posns_;
   time_table random_table_;
 };