Nick,
I am not sure I follow. Are you implying the following
"...&(big_array[1300])" an strong indication that big_array is stack
based, as opposed to heap based? It is possible to do such a thing as
stack based in Java, although quite uncustomary and require special
start-up parameters to force a larger stack to accommodate something so
large.
However, my interpretation of Don's description and code had me assuming
he was preallocating tons of heap space. If my assumption is accurate,
then I do the same thing in Java. As for then interpreting the bits - I
would do the identical mechanics as are done in C without any "new"
operator using several different techniques depending upon whether this
was a CPU or memory bottleneck.
Don,
So could you elaborate on where you are allocating space for big_array
in your code snippet below?
Jim
Nick Apperson wrote:
This is a very good design in my opinion. I was about to ask why you
used an index instead of a pointer until I saw that you were using a
pointer actually. Using global data like this highlights one of the
ways that C++ can blow away Java's requirement that everything must be
allocated on the heap.
On 1/19/07, *Don Dailey* <[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>> wrote:
On Fri, 2007-01-19 at 16:51 +0000, Eduardo Sabbatella wrote:
> Sorry, I didn't understand the big table but It sounds
> promissing. I don't understand how do you access to
> different variations ... it seems like a merge-sort
> array but not sure.
It forms a tree in memory, but it's just a huge array of nodes.
Each node has this:
move - the move played from parent to get us here
visits - number of times this node visited
score - number of wins from this node
first_child - index of node of first child
child_count - number of legal moves from this position.
(the move and child_count are 16 bits, everything else 32 bits,
total structure size = 32 + 32 + 32 + 16 + 16 bits. = 128 bits. )
if child_count == 0 the node has not yet been expanded.
If first child is stored at index 1300, for example and there
are 10 children, then
1300 - first child
1301 - second child
1302 - third child
.... etc.
first_child is actually a pointer in my implementation, but to
make this explanation clearer you can think of it as an index
into the global array. In the example the pointer addresses
array location 1300 .. in c -> (node_t *) child = &(big_array[1300]);
- Don
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