[opus] [RFC PATCH v1 1/2] Optimize repeated calls to opus_select_arch
Timothy B. Terriberry
tterribe at xiph.org
Tue Jan 20 11:05:07 PST 2015
Viswanath Puttagunta wrote:
> Instead, just optimize the opus_select_arch() such that only
> the first call to it takes more time, but subsequent calls to
> it are much faster.
This has been suggested before, but it is a bad idea. The patch posted
below is not thread-safe or even re-entrant. You can argue that the
results should always be the same, so it won't matter, but this is quite
hard to prove given the actual freedom a compiler has , and the races
will get reported as errors by automated race detection tools (such as
we use on Firefox), making the lives harder of everyone who has to deal
Fixing this requires introducing dependencies on threading libraries,
which are platform-specific (and may not even be available on some
platforms) and will make you lose performance.
So really I think the better solution is to modify the function
signatures, even if it looks like more typing.
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