Re: Performance problem with _SECURE_SCL=0

From:

"Carl Daniel [VC++ MVP]" <cpdaniel_remove_this_and_nospam@mvps.org.nospam>

Newsgroups:

microsoft.public.vc.stl

Date:

Mon, 12 Mar 2007 18:00:01 -0700

Message-ID:

<umUSurQZHHA.3984@TK2MSFTNGP02.phx.gbl>

"David Lowndes" <DavidL@example.invalid> wrote in message
news:2qnbv29phi5b27dp5pg4g9oa1rboktjp4d@4ax.com...

With the default settings there is not much difference but as I wrote in
my
original post, I don't use the default settings.
In the settings of the project, in the C++ section, I set the optimization
attributes as follows:
optimization = custom
inline function expantion = default
favor size or speed = favor fast code (/Ot)

Ouch, yes, those settings make a phenomenal difference and do result
in the apparent discrepancy you mentioned.

As to exactly where the difference is coming from I can't see the wood
for the trees in the find algorithm code and the CHECKED macros. :(

It's slower because using just /Ot effectively disables many optimizations.
If you compile with /Ot /Oy /Ob2 /Og /Ox you'll get results comparable to
simply use /O2 - which is really the right answer.

If you want to maximize speed, compile with /O2. Rare is the circumstance
where using the fine-grained optimization settings is the right answer.

-cd