Re: [Libmesh-users] small doc and efficiency update for ex 3 and 4

[edgar <edg...@cr...>]

On 2021-06-10 16:00, John Peterson wrote:
> On Wed, Jun 9, 2021 at 9:11 PM edgar <edg...@cr...> wrote:
> 
>> Hi,
>> 
>> I am humbly sharing something which I think would improve the
>> documentation and the logic of examples 3 and 4 a bit. I think that 
>> this
>> would apply to other examples as well. (I was planning to keep 
>> learning
>> from the examples, and have a more substantial contribution at the 
>> end,
>> but it has been like a month since I last touched libMesh, and I it
>> seems that I am going to be very busy in the next couple of months).
>> 
>> Thanks.
> 
> 
> Hi Edgar,
> 
> I agree with the updates to the code comments in both files, so thanks 
> for
> those. In the ex4 diff, it looks like you move the Ke, Fe declarations 
> from
> outside the for-loop over elements to inside? This is not likely to be 
> an
> optimization, though, since creating that storage once and "resizing" 
> it
> many times in the loop avoids dynamic memory allocations... the resizes 
> are
> no-ops if the same Elem type is used at each iteration of the for-loop. 
> If
> you have some performance profiling for this example that suggests
> otherwise, I'd be happy to take a look.

In all honesty, John, I did run a performance log on them, and the 
modification was faster, but I don't have it anymore. As I implied, my 
intention was to implement the changes in most examples, but I just 
haven't had the time. I can reproduce the logs, but I don't know when I 
will have the time for that :S (sorry :( ). I guess that the reduced 
time comes from the compiler recognising the variable as short-lived 
within the loop and avoiding the resizing of the matrices for each loop.

It may take some days before I reply.