[racket] Racket Virtual Machine runs out of memory

8 hours ago, Harry Spier wrote:
> I probably have to go the route you and others suggest.  But I think
> I still have a problem.  Even the single operation of
> MagickExportPIxels to export the pixel data of this page to
> manipulate fills at least 4/7 of the memory before failure.  And
> there is no guarantee that pages wont have more pixel data.  They
> probably will.  And as Matthias says the list doesn't seem "that
> large".

It looks like `MagickExportPixels' is something similar to the
deprecated `MagickGetImagePixels' -- so my guess is that you
interfaced this function in a similar way to how the latter is done in
ffi/examples/magick.  If these guesses are all valid, then the
important thing here is that there's no real need to convert the
resulting block of memory to a list of lists -- you can just create a
byte string of the appropriate size, then use it directly.  For
example, I added this:

  (defmagick* MagickExportImagePixels :
    _MagickWand (x : _long) (y : _long) (width : _ulong) (height : _ulong)
    (map : _string = "I") (storage-type : _StorageType = 'CharPixel)
    (block : _bytes = (make-bytes (* width height)))
    -> _status
    -> block)

(It's a bad hack, since it calls the function
`MagickExportImagePixels' but it really hard-wires the `map' and
`storage-type' arguments...)

With this, calling the function on an image returns a byte string with
the intensities (which is also -- I'm guessing -- what you're looking
for).  Now you can use the resulting byte string as-is, and directly
read its contents, manipulate it, and use it with other magick
functions.  This will save you on the redundant list allocation, and
will keep a single copy instead of several copies.  (And perhaps
there's also some magick function that can do the same with a single
bit/pixel to get the extra 8x saving factor.)


> Also I have 4 or 5 transformation stages of the pixel data.  Will
> putting in Garbage Collection commands to get rid of transformations
> of the data I've already used help?

(My guess is that it won't help.)


> What sets the amount of memory the Racket virtual machine uses.  Is
> it a Racket parameter, Is it a function of the amount of RAM in the
> machine?  Is this more a Windows problem and will switching to Linux
> help etc.?

If you're not using a 64 bit machine, then it might help to do that,
but I'd put this in the same category of not worth fighting with,
since you'll need some drastic changes anyway.

-- 
          ((lambda (x) (x x)) (lambda (x) (x x)))          Eli Barzilay:
                    http://barzilay.org/                   Maze is Life!