[Caml-list] Finalising bigarrays

[Caml-list] Finalising bigarrays

[Shivkumar Chandrasekaran]

Hi,

If anybody knows the answer to the following question I will appreciate 
learning of it:

I tried calling Gc.finalise on a bigarray and it did not raise an 
exception. Does that mean finalisation of bigarrays will work?

Thanks,

--shiv--

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Re: [Caml-list] Finalising bigarrays

[Damien Doligez]

On Mar 25, 2004, at 02:01, Shivkumar Chandrasekaran wrote:

> I tried calling Gc.finalise on a bigarray and it did not raise an 
> exception. Does that mean finalisation of bigarrays will work?

A bigarray is composed of two things: a heap-allocated descriptor
block that tells the number of dimensions, the layout, etc, and
contains a pointer to the data.  The data is in an out-of-heap
block.

When you call Gc.finalise, you are finalising the descriptor
block.  That would not matter if there was a one-to-one mapping
between descriptor blocks and data blocks, but sometimes the
data block is shared between bigarrays (when you call slice_left,
slice_right, sub_left, sub_right, or the reshape functions).

Your finalisation function is called when the bigarray itself
is not used any more by your program, but you should beware that
its data may be used by other bigarrays.  Hence your finalisation
function must not overwrite the data, unless you are really sure
that it is not shared.

-- Damien

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