Add more context information and print estimated runtime

include/benchmark/reporter.h

@@ -34,6 +34,9 @@ class BenchmarkReporter {
     double mhz_per_cpu;
     bool cpu_scaling_enabled;
 
+    double benchmark_min_time;
+    size_t benchmark_count;
+    size_t benchmark_repetitions;
     // The number of chars in the longest benchmark name.
     size_t name_field_width;
   };

src/benchmark.cc

@@ -802,8 +802,13 @@ void RunMatchingBenchmarks(const std::string& spec,
   context.mhz_per_cpu = CyclesPerSecond() / 1000000.0f;
 
   context.cpu_scaling_enabled = CpuScalingEnabled();
+  context.benchmark_count = benchmarks.size();
+  context.benchmark_min_time = FLAGS_benchmark_iterations ? 0.0
+                                : FLAGS_benchmark_min_time;
+  context.benchmark_repetitions = FLAGS_benchmark_repetitions;
   context.name_field_width = name_field_width;
 
+
   if (reporter->ReportContext(context)) {
     for (const auto& benchmark : benchmarks) {
       RunBenchmark(benchmark, reporter);

src/reporter.cc

@@ -14,9 +14,11 @@
 
 #include "benchmark/reporter.h"
 
+#include <cmath>
 #include <cstdio>
 #include <cstdlib>
 #include <iostream>
+#include <limits>
 #include <string>
 #include <vector>
 
@@ -113,6 +115,14 @@ bool ConsoleReporter::ReportContext(const Context& context) {
 #ifndef NDEBUG
   fprintf(stdout, "Build Type: DEBUG\n");
 #endif
+  if (std::abs(context.benchmark_min_time)
+        > std::numeric_limits<double>::epsilon()) {
+    double estimated_time = context.benchmark_count
+                          * context.benchmark_repetitions
+                          * context.benchmark_min_time
+                          * 1.4;
+    fprintf(stdout, "Estimated run time: %.0fs\n", estimated_time);
+  }
 
   int output_width =
       fprintf(stdout,