Archivers and SIMD ???

[Bohdy]

Sorry if this is a silly question, but why is it that archivers (rar, ace etc) seem to be the only software that hasn't taken advantage of SSE and other such things available in today's processors?

Is there no benefit to be gained?

 

[Simon F]

Sorry if this is a silly question, but why is it that archivers (rar, ace etc) seem to be the only software that hasn't taken advantage of SSE and other such things available in today's processors?

Is there no benefit to be gained?

Probably because the compression algorithms generally use the history of the previous data when determining how to compress the current item. It makes it very difficult to extract any parallelism.

(One exception is perhaps systems that use fixed tables, eg a fixed huffman table, but you still have the problem that different data are stored with variable numbers of bits which means you can't (easily) get item N+1 until you've worked out how many bits N uses).

 

[pcchen]

It is possible to use MMX/SSE for bit writers (using 64 bits arithmetic). However, I am not sure about its efficiency, I didn't try it.