About makefile

[jarunan at ascomp.ch]

Thank you very much, Satish.
Thank you very much, Brock Palen.

I am clear about it now.

Jarunan



Quoting Satish Balay <balay at mcs.anl.gov>:

> The reason we delete the .o files and force a recompile each time for
> examples is: not all dependencies are captured in our makefiles. For
> eg: when switching PETSC_ARCH, or [as developers] - if PETSc sources
> are changed for the same PETSC_ARCH. [examples don't have dependencies
> that would force a recompile]
>
> So its easier for us just to do recompile of examples each time - than
> keeping track of the above changes [which happen constantly for us
> developers]
>
> As users the above issue might not matter [as most use a single
> PETSC_ARCH, and the PETSC install hardly changes]. So - you can save
> this time by not deleting .o files - and doing 'make clean' - when
> you really need to reset.
>
> Satish
>
>
> On Fri, 9 Oct 2009, Brock Palen wrote:
>
>>
>>
>>
>> On Oct 9, 2009, at 7:05 AM, jarunan at ascomp.ch wrote:
>>
>> > Hello
>> >
>> > After the compilation, is it compulsory to delete .o file?
>> > Actually, once I found that .o file do not update unless I delete  
>>  it before
>> > recompiling. I might misunderstand. if not, I would like to know   
>> some reason
>> > behind.
>>
>> Make only recompiles files where the source file is newer than the resulting
>> file (the .o file).  Thus if you have not modified the source file for a .o
>> file, it will not be recompiled and will be relinked as is.  If you wish to
>> force everything to recompile (maybe new compiler options etc)    
>> then you need
>> to delete all your old .o .a .so and .mod files.  So they are recreated with
>> the new options.
>>
>> This is a feature of make, that is really helpful, it keeps you   
>> from having to
>> wait to recompile code that has already been compiled once, if it will not
>> change.
>>
>> Brock Palen
>> www.umich.edu/~brockp
>> Center for Advanced Computing
>> brockp at umich.edu
>> (734)936-1985
>>
>> >
>> >
>> > Thank you
>> > Jarunan
>> >
>> >
>> > --
>> > Jarunan Panyasantisuk
>> > Development Engineer
>> > ASCOMP GmbH, Technoparkstr. 1
>> > CH-8005 Zurich, Switzerland
>> > Phone : +41 44 445 4072
>> > Fax   : +41 44 445 4075
>> > E-mail: jarunan at ascomp.ch
>> > www.ascomp.ch
>> >
>> >
>> >
>>
>
>



-- 
Jarunan Panyasantisuk
Development Engineer
ASCOMP GmbH, Technoparkstr. 1
CH-8005 Zurich, Switzerland
Phone : +41 44 445 4072
Fax   : +41 44 445 4075
E-mail: jarunan at ascomp.ch
www.ascomp.ch