Re: variable particle number

From: luca tornatore <tornatore_at_ts.astro.it>
Date: Mon, 16 May 2005 21:07:30 +0200

sorry for the delay (i'm debugging too >:/ )

> You mean the `nextnode[]' array in Gadget1 ?

.. i was assuming that you're using gadget2. it isn't?
keeping the assumption: also in gadget2 there is a Nextnode[] array
which describes the complete tree-walk.

basically you have two moments to make a particle "visible" or
"invisible" to the tree construction/evaluation.
the first one is when the tree is built; so that, in
force_treebuild_single() you simply "mask" the particle i in the for(;;)
cycle. this way, all (side-length of tree nodes, multipole moments, hmax
etc) is being consistently computed (it is up to you to decide what
error will arise when multipoles are not updated).
a second moment is when the tree is updated (basically in
force_update_node_len_local() ). Then you have to take care about
multipole moments, bitflags etc, if i'm not misunderstanding what you're
doing. Moreover, you have to modify the Nextnode[] so that when the tree
is evaluated the particle i will not be included.. something like the
opposite than the force_add_star_to_tree() does.

of course you know all that, this was just (1) to make the readers that
don't have the knowledge to gain it and (2) to make discussion more
focused so that the readers that have the knowledge can quickly correct me.


> mmm... I don't know yet. The modified program even don't compiling.
> THIS is the rough reality. :)))

THIS is "hard"

> But yours confidence gives me the strength. Tank you!

you know.. they are only lines of code.. besides they are thousands and
thousands, *you* are the intelligent form of life :)

cheers,
luca
Received on 2005-05-16 21:11:58