Opportunity for speedup

Bobby Powers bobbypowers at gmail.com
Thu Feb 19 13:49:58 EST 2009

2009/2/19 Wade Brainerd <wadetb at gmail.com>:
> On Thu, Feb 19, 2009 at 1:22 PM, C. Scott Ananian <cscott at laptop.org> wrote:
>> I'd suggest just uncompressing the various image files and re-timing
>> as a start.  The initial implementation was uncompressed, but people
>> complained about space usage on the emulator images (which are
>> uncompressed).  The current code supports both uncompressed and
>> compressed image formats.  For uncompressed images, putting the bits
>> on the screen is an mmap and memcpy, so I can't imagine any
>> implementation being faster than that (it's possible, of course, that
>> what's stealing CPU is the shell's invocation of the client program;
>> recoding just that little part in C should be trivial, since it does
>> nothing but write to a socket IIRC.)
> I implemented a RLE compressor specifically for these 16bit image files the
> last time this question came up.  This can certainly be faster than memcpy
> since we are talking memory performance.

Can you explain this?  I don't think I have enough knowledge to
evaluate your claim.


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