Add new str_util::HumanReadableElapsedTime that formats a 'double seconds' value

using appropriate units based on the magnitude of the time interval, and add
tests for this.
Change: 132365945

3 files changed, 82 insertions, 0 deletions

diff --git a/tensorflow/core/lib/strings/str_util.cc b/tensorflow/core/lib/strings/str_util.cc
index 1c315655c1..8ae56b4906 100644
--- a/tensorflow/core/lib/strings/str_util.cc
+++ b/tensorflow/core/lib/strings/str_util.cc
@@ -18,6 +18,7 @@ limitations under the License.
 #include <ctype.h>
 #include <vector>
 #include "tensorflow/core/lib/strings/numbers.h"
+#include "tensorflow/core/lib/strings/stringprintf.h"
 
 namespace tensorflow {
 namespace str_util {
@@ -334,5 +335,58 @@ bool SplitAndParseAsInts(StringPiece text, char delim,
   return true;
 }
 
+string HumanReadableElapsedTime(double seconds) {
+  string human_readable;
+
+  if (seconds < 0) {
+    human_readable = "-";
+    seconds = -seconds;
+  }
+
+  // Start with us and keep going up to years.
+  // The comparisons must account for rounding to prevent the format breaking
+  // the tested condition and returning, e.g., "1e+03 us" instead of "1 ms".
+  const double microseconds = seconds * 1.0e6;
+  if (microseconds < 999.5) {
+    strings::Appendf(&human_readable, "%0.3g us", microseconds);
+    return human_readable;
+  }
+  double milliseconds = seconds * 1e3;
+  if (milliseconds >= .995 && milliseconds < 1) {
+    // Round half to even in Appendf would convert this to 0.999 ms.
+    milliseconds = 1.0;
+  }
+  if (milliseconds < 999.5) {
+    strings::Appendf(&human_readable, "%0.3g ms", milliseconds);
+    return human_readable;
+  }
+  if (seconds < 60.0) {
+    strings::Appendf(&human_readable, "%0.3g s", seconds);
+    return human_readable;
+  }
+  seconds /= 60.0;
+  if (seconds < 60.0) {
+    strings::Appendf(&human_readable, "%0.3g min", seconds);
+    return human_readable;
+  }
+  seconds /= 60.0;
+  if (seconds < 24.0) {
+    strings::Appendf(&human_readable, "%0.3g h", seconds);
+    return human_readable;
+  }
+  seconds /= 24.0;
+  if (seconds < 30.0) {
+    strings::Appendf(&human_readable, "%0.3g days", seconds);
+    return human_readable;
+  }
+  if (seconds < 365.2425) {
+    strings::Appendf(&human_readable, "%0.3g months", seconds / 30.436875);
+    return human_readable;
+  }
+  seconds /= 365.2425;
+  strings::Appendf(&human_readable, "%0.3g years", seconds);
+  return human_readable;
+}
+
 }  // namespace str_util
 }  // namespace tensorflow
diff --git a/tensorflow/core/lib/strings/str_util.h b/tensorflow/core/lib/strings/str_util.h
index 4a519425d4..8198b7c541 100644
--- a/tensorflow/core/lib/strings/str_util.h
+++ b/tensorflow/core/lib/strings/str_util.h
@@ -80,6 +80,15 @@ string Uppercase(StringPiece s);
 // set of characters that can be used as word boundaries.
 void TitlecaseString(string* s, StringPiece delimiters);
 
+// Converts a time interval as double to a human readable
+// string. For example:
+//   0.001       -> "1 ms"
+//   10.0        -> "10 s"
+//   933120.0    -> "10.8 days"
+//   39420000.0  -> "1.25 years"
+//   -10         -> "-10 s"
+string HumanReadableElapsedTime(double seconds);
+
 // Join functionality
 template <typename T>
 string Join(const T& s, const char* sep);
diff --git a/tensorflow/core/lib/strings/str_util_test.cc b/tensorflow/core/lib/strings/str_util_test.cc
index a0494190fd..6481e5cfd7 100644
--- a/tensorflow/core/lib/strings/str_util_test.cc
+++ b/tensorflow/core/lib/strings/str_util_test.cc
@@ -287,4 +287,23 @@ TEST(TitlecaseString, Basic) {
   ASSERT_EQ(s, "Dense");
 }
 
+TEST(HumanReadableElapsedTime, Basic) {
+  EXPECT_EQ(str_util::HumanReadableElapsedTime(-10), "-10 s");
+  EXPECT_EQ(str_util::HumanReadableElapsedTime(-0.001), "-1 ms");
+  EXPECT_EQ(str_util::HumanReadableElapsedTime(-60.0), "-1 min");
+  EXPECT_EQ(str_util::HumanReadableElapsedTime(0.00000001), "0.01 us");
+  EXPECT_EQ(str_util::HumanReadableElapsedTime(0.0000012), "1.2 us");
+  EXPECT_EQ(str_util::HumanReadableElapsedTime(0.0012), "1.2 ms");
+  EXPECT_EQ(str_util::HumanReadableElapsedTime(0.12), "120 ms");
+  EXPECT_EQ(str_util::HumanReadableElapsedTime(1.12), "1.12 s");
+  EXPECT_EQ(str_util::HumanReadableElapsedTime(90.0), "1.5 min");
+  EXPECT_EQ(str_util::HumanReadableElapsedTime(600.0), "10 min");
+  EXPECT_EQ(str_util::HumanReadableElapsedTime(9000.0), "2.5 h");
+  EXPECT_EQ(str_util::HumanReadableElapsedTime(87480.0), "1.01 days");
+  EXPECT_EQ(str_util::HumanReadableElapsedTime(7776000.0), "2.96 months");
+  EXPECT_EQ(str_util::HumanReadableElapsedTime(78840000.0), "2.5 years");
+  EXPECT_EQ(str_util::HumanReadableElapsedTime(382386614.40), "12.1 years");
+  EXPECT_EQ(str_util::HumanReadableElapsedTime(DBL_MAX), "5.7e+300 years");
+}
+
 }  // namespace tensorflow