Joshua 'Schwa' Gargus <schwa at cc.gatech.edu> wrote:

Hi Joshua,
you wrote:
>
> I am using ReferenceStream to serialize some objects, the bulk of
> whose memory usage is in the form of B3DRotationArrays and
> B3DMatrix4x4Arrays (implemented exactly as B3DRotationArray, except
> the class-side method #contentsClass answers B3DMatrix4x4).
>
> I am using a ReferenceStream on top of a RWBinaryOrTextStream.  This
> is so I can create a ZipArchive containing several serialized objects
> without having to write a temporary file to disk, and then add it to
> the archive.
>
> I have found that the performance is much worse when the
> ReferenceStream is on top of an RWBinaryOrTextStream instead of a
> StandardFileStream (by a factor of about 20).  This appears to be
> because StandardFileStream uses a BitBlt-based hack to improve
> performance in #nextWordsPutAll:, while RBBinaryOrTextStream defaults
> to the implementation in Stream.
I think that StandardFileStream is fast because it has a very efficient
inplementation for  nextPutAll:. The method Stream>>nextPutAll:, which
is inherited by most subclasses, copies the elements of its argument
one by one which is not a very efficient solution. (See more about
this below [proposal2])
>
> My questions are:
>
> 1) Is there any reason why the StandardFileStream implementation shouldn't
> be used in RWBinaryOrTextStream, or even in Stream?
>
> 2) I tried doing #1, and ran into trouble because my new
> implementation of #nextWordsPutAll: calls
RWBinaryOrTextStream>>nextPutAll:,
> which sends #asString to the byte-swapped B3DRotationArray copy, which
> doesn't do anything sensible at all.  Instead of cloning the
> B3DRotationArray, could I copy its bits into a ByteArray before
> swapping bytes?  What is the easiest way to copy word data into a
> ByteArray?
>
The buffer of RWBinaryOrTextStream is *always* a string - even when the
instance variable  isBinary contains the value  true. I conclude that a
local implementation of  RWBinaryOrTextStream>>nextWordPutAll:
has to call  #nextPutAll:  with a string-valued argument.
The attached file  proposal1.cs  contains a local implementation of
nextWordPutAll:  and auxiliary definitions in B3DInplaceArray
and WordArray.  You see that I convert the B3DRotationArray
first into a WordArray, then into a ByteArray (this is the conversion
that handles the endianess issue) and finally into a String.

RWBinaryOrTextStream  has a lot of users, I am not sure that this
change will not create problems elsewhere. Such problems can be
caused by missing definitions of method  asWordArray.

Now a word about WriteStream>> nextPutAll:

You message clearly says that you need speed. I think that it is
possible to speed up  WriteStream>nextPutAll: This method iterates
over the argument collection when it has to grow the collection it
writes to. The use of a grow function is the better solution
because it allows the use of  the very fast
String>>replaceFrom:to:with:startingAt:

The file  proposal2.cs  contains this change.

Your message indicates that you have code to message execution times
with an example of realistic size. Given that this is true, I would like
to ask you measure execution times first
 -> with proposal1.cs  only
and then
 -> with proposal1.cs and proposal2.cs together.
I expect that the changes in  proposal2.cs  do a lot to speed up
your application.

Hope this helps. If it does not work, please do not hesitate to
tell me where the problems are.

Greetings, Boris
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