Re: Don't pass by reference to non-const?

From:
James Kanze <james.kanze@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Sat, 8 May 2010 16:27:13 -0700 (PDT)
Message-ID:
<c8d0f72a-365f-421d-859f-971db9e0357f@i10g2000yqh.googlegroups.com>
On May 8, 4:43 pm, "Balog Pal" <p...@lib.hu> wrote:

"James Kanze" <james.ka...@gmail.com>

I love it when people comment about things they know nothing
about.


... or fail to read minds auto-correcting misleading forum
comments?

The compiler can't always use RVO. Our two versions were:

std::vector<double> v(...);
for (... lot's of iterations ... )
{
// calculate some values based on the current contents
// of v.
v = some_function(... the calculated values ...);
// ...
}

as opposed to

std::vector<double> v(...);
for (... lot's of iterations ... )
{
// calculate some values based on the current contents
// of v.
some_function(&v, ... the calculated values ...);
// ...
}


In this example you clearly use the vector as INOUT parameter,
and have a performance gain from that fact.


In this example (in the actual code), the vector is a pure
output parameter.

Originally we were talking about OUT parameters...


So was I.

--
James Kanze

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