[FLASH-USERS] Problem with Compiling Flash3.0

[Seyit Hocuk]

Hi Nathan,

> In your case, did the number of vectorization messages decrease by using the "-vec-report0"
> option?
>   

Only if I don't use -ipo or -fast (contains -ipo). Because -ipo puts 
these remarks at the end wheter you used -vec-report or not.

> But, it may be worth comparing the
> performance (time-to-completion) of code that is compiled with and
> without these optimizations.  My recommendation would be to look at
> the documentation for your compiler, and select some specific
> optimizations instead of simply using "fast".  (It sounds like you may
> have already done this.)  

I did indeed. I also compared with different optimizations (with/without 
-ipo and/or -fast). My initial quick checks showed that computation 
speed is always unaffected.

> I have a feeling that you will get a bigger
> performance boost from the vectorization than the interprocedural
> optimizations, so I would start there first.
>   

I didn't have any performance boost. It was exactly the same. At-least 
in the initial parts of my simulation.


There is one huge problem that I noticed though. Normally I am always 
doing simulations on my own computer or at the cluster available to me. 
However, now that I am doing on this new computer with this new 
compiler, my initial results are different and the difference seems to 
grow bigger during the simulation. I use exactly! the same initial 
conditions. But I immediately notice that refinement is different 
(refines less quicker) and dtHydro is slightly different and growing 
more different compared to my computer.

Could this be due to the fact that the new machine is 64 bit and mine is 
32 bit and thus more precise? Although of-course the compiler is also 
different as are the libraries (Hdf5 and Mpich) as is the operating system.

Seyit



>
> - Nathan
>
>
> On Tue, Jul 15, 2008 at 7:50 AM, Seyit Hocuk <seyit at astro.rug.nl> wrote:
>   
>> Hi,
>>
>> I reinstalled everything and it seems to work! The annoying remarks of loops
>> being vectorized is gone if I put -vec-report0 and remove the -fast option.
>> I tested and found that the -ipo within the -fast option is the cause of
>> this report output. I hope that by removing this -ipo (which in my compiler
>> is shown as -ipo[n]), it doesn't create a different problem. At the moment
>> it looks like it works fine now. Is it dangerous to do it like this?
>>
>> Thanks to all the people who replied, Tomek, Rusty, Nathan, Chris,Tomek
>> again, Brock and Anshu.
>>
>> Kind regards,
>> Seyit
>>