On Thu, 22 Jan 2009 22:40:25 -0800 Greg Lindahl <lind...@pbm.com> wrote:
> On Fri, Jan 23, 2009 at 11:03:46AM +0500, amjad ali wrote: > > > (1) Which debugger would be easy and effective to use for above? > > print *, > openmpi spawns several processes so you options are pretty much print or pausing you programs at startup and attaching the debugger to a running program (problematic). Note though that with print you may miss timing issues. > > (2) Which of the folliwng two ways of using arrays is more efficient > > with respect to memory and function-call-overheads or other overheads: > > (i) We should keep the arrays ALLOCATABLE and then > > before return from the subroutines, DEALLOCATE the local arrays. > > or (ii) We should keep the local arrays fix-sized as > > much as we can. (Will the memory is deallaocated/freed automatically > > on return from the subroutine?). > The problem with (ii) is that the arrays are allocated on the stack which is of limited size. If the arrays are very large this may cause problems. > In general (ii) is faster: the compiler can generate better code if it > knows the size of the arrays. This is always possible with (ii) and > only sometimes with (i). > If you use loops with constant number of iterations the same speedup can also usually be achieved (I've seen dramatic differences due to dropping the conditional at each loop iteration) > With (ii) the memory will be freed on return from the subroutine, with > most modern compilers. With (i) the arrays will also be automagically > freed on exit from the subroutine. > > -- greg > > > _______________________________________________ > Beowulf mailing list, Beowulf@beowulf.org > To change your subscription (digest mode or unsubscribe) visit > http://www.beowulf.org/mailman/listinfo/beowulf > _______________________________________________ Beowulf mailing list, Beowulf@beowulf.org To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
