RE: [GD-Windows] forcing value to bool 'true' or 'false' (perform ance warning)

[Tom F. <to...@mu...>]

You're surely not going to tell me that

bool b = i != 0;

doesn't involve a conditional.


Anyway, I remember somebody coming up with this:

bool b = ((unsigned int)(a|-a))>>31;

Whether in practice it's faster or not, I don't know, but there's no
conditional jumps required.


Tom Forsyth - purely hypothetical Muckyfoot bloke.

This email is the product of your deranged imagination,
and does not in any way imply existence of the author.

> -----Original Message-----
> From: Tom Hubina [mailto:to...@3d...]
> Sent: 23 April 2002 02:22
> To: gam...@li...
> Subject: Re: [GD-Windows] forcing value to bool 'true' or 'false'
> (performance warning)
> 
> 
> At 06:04 PM 4/22/2002, Rich wrote:
> >Well, the compiler will generate code to convert an int (4 
> bytes) to a
> >bool (usually 1 byte), whether or not it matters for performance is
> >dubious.
> >
> >You can eliminate the warning by doing 'bool p = i ? true : false;'
> 
> Icky. You don't need conditionals for this.
> 
> When I convert between int and bool I've been using the 
> following to get 
> rid of the warning:
> 
> bool p = i != 0;
> 
> or in the case of Win32 API stuff:
> 
> bool p = i != FALSE;
> 
> In any case ... the performance issue for most cases is 
> probably minimal. I 
> would only be concerned if I was doing it inside a tight loop 
> that got 
> called a lot and was actually showing up as a spike when 
> profiling. When in 
> doubt, check the assembly.
> 
> Tom
> 
> 
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