Author: Uri Blass
Date: 03:08:54 08/21/03
Go up one level in this thread
On August 21, 2003 at 05:40:41, Daniel Clausen wrote:
>On August 21, 2003 at 05:16:17, Uri Blass wrote:
>
>[snip]
>
>
>>I payed attention to the fact that b and c can never happen if a does not
>>happen so I cahnge it to
>>if a
>>{
>>...
>> if b
>> {
>>...
>> }
>> if c
>> {
>>...
>> }
>>}
>
>If b and c can only happen in case a happens, I definitely would write it like
>that. (as opposed to the flattened version) But not because of a potential speed
>gain but because it's most likely also clearer to read. (at least for me)
>
>Three if-statements in a row are independant in my understanding. If they're
>not, I would replace them with a switch/case, make use of 'else if' instead of
>normal ifs or nest them as in your example. Which one of the 3 possibilities of
>course depends on the concrete case.
>
>Did you measure how much speed you gained in your case? And where approx are
>these if-statements? (if they're not in eval, I can't image you would notice
>_any_ speed difference)
>
>Sargon
The if were in updating arrays in my makemove.
The speed improvement was small(I think less than 1% speed improvement but I
could see the program run faster)
Note that I added more arrays to update incrementally in my makemove.
In the relevant case I start with
i=infodirections[sq] because I do not like to call infodirection[sq] again and
again;
i is a number that tells me the direction that a king in square sq can goto(in
case that the board is empty)
for example when sq=0 there are only 3 directions that it can go so only 3 bits
are 1.
The if are about directions and the point is that if
one direction is impossible I know that other 2 directions are also impossible.
If the king cannot go backward than the king cannot go backward in diagnol
direction.
The result is that instead
if (i&1)
{
...
}
if (i&2)
{
...
}
if (i&4)
{
...
}
I have
if (i&1)
{
...
if (i&16)
{
.....
}
if (i&64)
{
...
}
}
Note that it may be also better to get rid of the magic numbers and use
if (i&kingup)
{
...
if (i&kingleftup)
{
....
}
if (i&kingrightup)
{
...
}
}
Uri
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