Re: By Reference
- To: mathgroup at smc.vnet.net
- Subject: [mg105440] Re: By Reference
- From: David Bailey <dave at removedbailey.co.uk>
- Date: Wed, 2 Dec 2009 06:28:56 -0500 (EST)
- References: <hf2mrq$ie9$1@smc.vnet.net>
snirga wrote:
> Hi All,
>
> I am implementing a "call by reference" in Mathematica using HoldFirst
> in order to send a huge matrix into a function.
>
> I wanted to verify that Mathematica doesn't create a memory copy of
> this matrix once it is being sent to the function.
>
> Thanks
>
> Snir
>
I presume your function is intended to modify elements of the array -
otherwise no copy is likely to take place. Defining a function such as:
SetAttributes[foo,HoldFirst]
foo[arr_Symbol]:=Module[{},
..
..
..
arr[[j]]=42;
..
..
last operation;
]
should do what you want. Note that your function is modifying the
original array directly, and so should not pass back a return value
(well not the array value at any rate).
Note that you can use MemoryInUse to explore what is happening, but you
must be careful not to get copies of the array in your history.
David Bailey
http://www.dbaileyconsultancy.co.uk