Re: [ros-dev] Speed Tests (was: ping Alex regarding log2() for scheduler)

[Royce Mitchell III]

Alex Ionescu wrote:

>  
>  Addon = 16;
>  if ((IntMask = Mask >> 16)) {
>      Addon = 0;
>      IntMask = Mask;
>  }
>  if (IntMask && 0xFFFFFF00) {
>      Addon += 8;
>  }
>  HighBit = LogTable256[(Mask >> Addon)] + Addon;
>  
methinks there's bugs there, use this instead:

int highest_bit_tabled ( unsigned int i )
{
    int ret = 0;
    if ( i > 0xffff )
        i >>= 16, ret = 16;
    if ( i > 0xff )
        i >>= 8, ret += 8;
    return ret + LogTable256[i];
}

also, FWIW, I've tried the following three tests:

( i > 0xffff )

( i & 0xffff0000 )

( i >> 16 )

and the first is the fastest on my a64