Failed of seeing transitions in OpenMP* application when using gnu compiler to build?

When use gnu compiler to build OpenMP* application, and use VTune™ Amplifier XE 2013’s “Thread Concurrency” or “Locks and Waits” to analyze – there is no transitions in timeline panel of bottom-up report. 
# g++ -g -fopenmp pi.cpp -o pi.g++
# amplxe-cl -collect concurrency -- ./pi.g++

See unexpected result, screenshot attached file name transitions1.jpg.

The reason is that Intel(R) OpenMP* library should be linked into application, if you don’t use Intel C/C++ composer XE.

Rebuild OpenMP application with option “-liopm5”, if you have installed Intel C/C++ Composer XE 2013.
# g++ -g -fopenmp -liomp5 pi.cpp -o pi.g++
# amplxe-cl -collect concurrency -- ./pi.g++

You should see transitions appeared in bottom-up report, see screenshot attached file name transitions2.jpg.

Image icon transitions1.jpg197.42 KB
Image icon transitions2.jpg188.55 KB
File omp_pi.c501 bytes
For more complete information about compiler optimizations, see our Optimization Notice.