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syzygy wrote:I would not recommend the for() solution, though

Michael Sherwin wrote:The initBoard variable is absolutely needed

Ras wrote:

Michael Sherwin wrote:The initBoard variable is absolutely needed

It isn't. You could eliminate it because the whole initialisation only takes place for the 64 centre squares of the board, which is checked via the initboard.

So why not using eight dedicated loops? The first runs from 21 to 28, the second from 31 to 38, the third from 41 to 48 and so on. You would even eliminate the superfluous initboard checks when i is 29 or 30, or 39 or 40.

If you put each of these row-wise loops in a parametrised macro, you'd eliminate the code duplication that directly rolling out these 8 loops would bring.

Okay, now I follow!

Michael Sherwin wrote:

Ras wrote:

Michael Sherwin wrote:The initBoard variable is absolutely needed

It isn't. You could eliminate it because the whole initialisation only takes place for the 64 centre squares of the board, which is checked via the initboard.

So why not using eight dedicated loops? The first runs from 21 to 28, the second from 31 to 38, the third from 41 to 48 and so on. You would even eliminate the superfluous initboard checks when i is 29 or 30, or 39 or 40.

If you put each of these row-wise loops in a parametrised macro, you'd eliminate the code duplication that directly rolling out these 8 loops would bring.

Okay, now I follow!

for&#40;sq = 0, sq < 64, sq++) &#123;
  y = sq / 8; x = sq - y * 8;
  k = y * 10 + x + 1;
  ...
&#125;
  

Michael Sherwin wrote:Or better just changing the direction!

#define RANK64(x) (x >> 3)
#define FILE64(x) (x & 0x07)
...
y = RANK64(sq);
x = FILE64(sq);

Ras wrote:

Michael Sherwin wrote:Or better just changing the direction!

That's even nicer because it's clearer. And you could make the loop count down instead of counting up. And
y = sq / 8; x = sq - y * 8;
could be replaced by
y = sq >> 3; x = sq & 0x07;
though the compiler will likely do the first replacement automatically.

Or, and that would be even more readable:

Code: Select all

#define RANK64(x) (x >> 3)
#define FILE64(x) (x & 0x07)
...
y = RANK64(sq);
x = FILE64(sq);

Ras wrote:

Code: Select all

#define RANK64(x) (x >> 3)
#define FILE64(x) (x & 0x07)

#define RANK64(x) ((x) >> 3)
#define FILE64(x) ((x) & 0x07)

Ras wrote:

Ras wrote:

Code: Select all

#define RANK64(x) (x >> 3)
#define FILE64(x) (x & 0x07)

Subtle oppurtunities for bugs upon a second glance. If the x that is handed over isn't a variable, but e.g. a sum, then this will go wrong. Should be:

Code: Select all

#define RANK64(x) ((x) >> 3)
#define FILE64(x) ((x) & 0x07)

#define SQUARE120(x) (((x) >> 3 * 10) + (((x) & 7) + 1))

Michael Sherwin wrote:

Code: Select all

#define SQUARE120(x) (((x) >> 3 * 10) + (((x) & 7) + 1))

#define SQUARE120(x) ((((x) >> 3) * 10) + ((x) & 7) + 1)