Clock Tree Latency Calculation Difference between reportClockTree & report_timing

Clock Tree Latency Calculation Difference between reportClockTree & report_timing.

Hi, ALL:

I found that using SOC Encounter 52 update 5, the clock tree latency report generated by reportClockTree -clkRouteOnly is quite different from  the report_timing command. The detailed scenario is as follow:

1. I use setCTSMode -routeClkNet -useCTSRouteGuide (I didn't type the exact option, just its meaning)
2. Then Report the clock tree, the latency is 1400-1500ps.
3. I then use report_timing to report certain timing path to get certain register clock pin latency.
4. I search the clock tree report generated by reportClockTree, found that the latency is 200ps more than the 'report_timing' result.
5. I use encounter db command & get_timing command to write a script calculating all the register clock pin latency, found the latency is around 1200-1350ps.( my test block has just 1 clock, hoho....)
6. I carefully checked my script & option, nothing strange........

Can anybody tell me why, need help.