Help in understanding -log_summary output

[Barry Smith]

On Jul 28, 2008, at 3:13 PM, Rafael Santos Coelho wrote:

>
>  Global gives the percentage of the  time/flops/messages/total  
> message data/reductions in this event out of the TOTAL RUNTIME  
> (basically from
> PetscInitialize() to PETScFinalize(). So 5 percent of the total  
> runtime was in this event and 99 percent of the messages (99 is  
> rounded down from 100
> so it is probably essentially 100%).
>
> I see, but then how come the sum of all those global percentages  
> don`t equal 100%?

   You mean, for example, why doesn't the global %T of MatMult() +  
global %T of VecNorm() + global %T of VecScatterBegin() etc etc
add up to 100%?

    This is because many of the events are imbedded inside other  
events (sometimes in complicated ways). For a simple example
MatMult() in parallel uses VecScatterBegin/End()....

    Barry