[log] Set duration to 0 when next time stamp is smaller

  Due to the circular buffer, when overwriting previously logged data,
  the iteration duration could be highly negative. Set it to zero in that case.

Author: florent-lamiraux

src/log.cpp

@@ -223,7 +223,8 @@ void Log::saveVector(std::string &fileName, std::string &suffix,
         dt = StoredData_.timestamp[0] -
              StoredData_.timestamp[profileLog_.length - 1];
       } else
-        dt = StoredData_.timestamp[k] - StoredData_.timestamp[k - 1];
+        dt = std::max(0., StoredData_.timestamp[k] -
+                      StoredData_.timestamp[k - 1]);
       writeToBinaryFile(aof, StoredData_.timestamp[i], dt, avector, idx, size);
       idx = (idx + size) % N;
     }