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Re: .f90 runs slower than .f
On Aug 3 2012, Jerry DeLisle wrote:
For what it is worth, -fdump-tree-original with the above flags gives
exactly identical output for the .f and .f90 case.
The .o files differ in length by 8 bytes. I suspect due to the source
file name difference.
There are several reasons why running even an identical executable on
identical data can show very different timings, but none of the common
ones have anything to do with the compiler.
Irrelevant changes in the environment can cause cache line conflicts
to appear, and even less relevant ones on other parts of the system
can cause memory bank or TLB clashes. Tracking down the former is
just about possible for most programmers, but the latter are possible
only if the hardware performance counters help. If they don't, the
depths of hacking needed to track down the issue are beyond even the
imagination of most programmers. The OP is not advised to go there!
Regards.
Nick Maclaren.