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Re: Some new functions [message #29870 is a reply to message #29827]

Thu, 25 November 2010 16:43

Novo
Messages: 1358
Registered: December 2006

Ultimate Contributor

dolik.rce wrote on Sat, 20 November 2010 14:55

Fun fact: I tried to come up with optimal solution for Even() and all of the following appear to have same speed as the one from Koldo (with gcc optimal+speed flag):

inline bool even1(int val)		{return !(val&1);}
inline bool even2(int val)		{return ~val&1;}
inline bool even3(int val)		{return !(val%2);}

Without the speed flag even2() seems to be slightly faster.

Also val%2 and val&1 for Odd() yields the same speed in both cases Smile

However, the proposed RoundEven() function is suboptimal thanks to the branching. Even though it won't probably be used often, I would suggest faster version:

inline int roundeven(int val)	{return ((1+val)>>1)<<1;}
//for completeness also rounding to odd numbers:
inline int roundodd(int val)	{return ((val>>1)<<1)+1;}

Best regards,
Honza

Hi Honza,

I posted a link to a collection of optimized functions here http://www.ultimatepp.org/forum/index.php?t=msg&th=5683& amp;start=0&

It looks like it might be helpful for your experiments.

Regards,
Novo

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