Re: [Boost-users] large variant performance compared (50 elements)

Subject: Re: [Boost-users] large variant performance compared (50 elements)
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2011-01-08 15:46:01

AMDG

On 1/8/2011 11:56 AM, Paul wrote:
> I've done some testing based on the suggestions:
>
> Adding a destructor to the 'dummy' types doesn't seem to make a 
> difference.

Now that I've looked through the code, it's the
copy constructor and default constructor that
matter.

> Adding boost::blank as the first type however makes a hugh difference:
> <snip>
>
> Drawback of this approach seems to be that each visitor needs to have 
> an operator()() receiving a boost::blank&; not a big problem anyway.
>
> I failed to apply the patch-file on the 1.38 revision; either there is 
> a problem with the patch.exe that i downloaded (for win32) or the 
> patch-file doesn't match this revision. When you can send me a 
> modified variant.hpp based on the file attached, then i will be happy 
> to run some tests.

I was able to apply the patch.  I've attached it.  (zipped since
it's rather large.)

> I was wondering whether the found behavior is a bug or not; after all 
> it seems to be functionally correct but it just doesn't scale very 
> well. When this problem can be fixed in the variant.hpp then i guess 
> that's preferred but what are the consequences at functional level 
> and/or runtime performance?

The functionality should be unaffected.  The runtime
cost is one call through a function pointer.

In Christ,
Steven Watanabe