Re: Doubts about Snapshot

[Partha Dasgupta]

1 and 2 -> The algo says the marker is processed before any other messages are sent or received. In other words -- when tha marker is detected (by the runtime system or library) the process is frozen, a checkpoint taken (if needed) the marker is propagated (if needed) channel  state is recorded -- and then the process is restarted.

2. Yes they can change simultaneously. Which happens for unrelated or concurrent events. Which means they can be assumed to have happened in any order. So we assume P1 changes first or P2 changes first. 

Partha Dasgupta,
ASU/CIDSE/Computer Science & Eng. 
EMail: par...@asu.edu
http://cactus.eas.asu.edu/partha

On Wed, Nov 29, 2017 at 9:52 PM, Kamesh Vankayala <kvan...@asu.edu> wrote:

Hi Professor,

I've some doubts about the problem you've explained in the class:

1) In the above example, when marker returns from process P2(in  5th row), Is it compulsory that the marker should come into channel C2 before the message m3 comes into C2 ??

Or, the marker could be after messaageg m3 while it is returning to the process P1.

2) If we insert marker in process P1 in state A (in second row), will it immediately send a marker onto channel C1 irrespective of presence of send() in the code of process P1? i

3) Can the states of processes P1 and P2 change simultaneously i.e, A -> B and  D -> C respectively?

Could you please clear my doubts ?

Thanks && Regards,

Kamesh