[MPICH] question on progress engine in MPICH2

[Yu Yang]

Hello, everyone,

I had thought that the MPI progress engine code is in 
src/mpid/ch3/channels. Different communication scheme will use the
code in different directory. And the related functions are

MPIDI_CH3_Progress_init
MPIDI_CH3_Progress_wait
MPIDI_CH3_Progress_test
MPIDI_CH3_Progress_finalize

But it is unclear to me that where these functions are used. As for
MPID_CH3_Progress_wait, using grep, I only found it used in
MPID_Probe.  How is the progress engine used for MPID_Send,
MPID_Recv etc?   Is there documentation that I look at?

Thank you very much!

Best wishes,
Yu