From: Didier Verna
Subject: array initialization: dimension list not constant
Date: Fri, 31 Mar 2006 14:06:04 +0000
Message-ID: <muxmzf6k8tv.fsf@uzeb.lrde.epita.fr>

        Just to be sure ...


in something like (make-array (* width height) ...)

CMUCL might complain that the dimension list is not constant, so it cannot
open-code the array creation routine.


This has an impact on the performance of the array creation, but not on
subsequent operations onto the array, right ?

THX

-- 
Didier Verna, ······@lrde.epita.fr, http://www.lrde.epita.fr/~didier

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From: Barry Margolin
Subject: Re: array initialization: dimension list not constant
Date: Fri, 31 Mar 2006 16:28:51 +0000
Message-ID: <barmar-486BCF.11285131032006@comcast.dca.giganews.com>

In article <···············@uzeb.lrde.epita.fr>,
 Didier Verna <······@lrde.epita.fr> wrote:

>         Just to be sure ...
> 
> 
> in something like (make-array (* width height) ...)
> 
> CMUCL might complain that the dimension list is not constant, so it cannot
> open-code the array creation routine.
> 
> 
> This has an impact on the performance of the array creation, but not on
> subsequent operations onto the array, right ?

If the compiler knows the size of the array, it may be able to optimize 
some array bounds checks, perhaps even warn you about exceeding them.  
For instance, it could conceivably reject this code:

(let ((new-array (make-array 3)))
  (setf (aref new-array 4) 'x)
  new-array)

-- 
Barry Margolin, ······@alum.mit.edu
Arlington, MA
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