dpk@BRL-VGR.ARPA (07/05/84)
From: Doug Kingston <dpk@BRL-VGR.ARPA> The programs compact and uncompact on Berkeley 4.2 are horribly expensive to use. They use around 6 times as much CPU time as an equivalent program on the PDP11. This is ridiculous. File was 10500 chars (larger files are no better) 11/70 pack 1.7u 0.7s 0:03r 26% compaction unpack 0.9u 0.6s 0:02r VAX 780 compact 7.9u 0.3 0:08r 27% compaction uncompact 5.9u 0.3s 0:06r I also had a compacted file of 873000 chars that took 610 seconds of CPU time to uncompact. This is silly. I profiled compact and it looks like its ripe for improvement. Has anyone attempted to fix this? -Doug-
gwyn@BRL-VLD.ARPA (07/05/84)
From: Doug Gwyn (VLD/VMB) <gwyn@BRL-VLD.ARPA> Personally I use the System V pack & unpack/pcat.
mark@umcp-cs.UUCP (07/07/84)
Rather than improve compact/umcompact, better to just port pack/unpack. That is what we did. Pack/unpack run fine on vaxes. -- Spoken: Mark Weiser ARPA: mark@maryland CSNet: mark@umcp-cs UUCP: {seismo,allegra}!umcp-cs!mark
dan@idis.UUCP (07/10/84)
I get the impression from the manual page for compact/uncompact that the programs might update internal encoding/decoding tables after each byte is processed. If this is the case, changing the code to update the internal tables less often might improve performance. This change would also make the new compact/uncompact incompatible with the old versions (possibly a serious problem considering that one major use of compact/uncompact is to reduce uucp xfer times for large files). Dan Strick [decvax|mcnc]!idis!dan
dgs@hpfclv.UUCP (dgs) (07/12/84)
Look in net.sources for utah-cs!thomas's listing of 'compress' I haven't tried it but he claims that is is much faster and better than either 'compact' of 'pack'. Try it, you'll like it. Dan Schmidt (hpfcla!dgs)
ka@hou3c.UUCP (Kenneth Almquist) (07/13/84)
Even the System V pack/unpack can be improved. The unpack code processes one bit at a time; I got about a fourfold speed improvement by modifying the code to pull off 8 bit chunks. Before that I recoded the unpack routine in PDP-11 assembly language which resulted in a comparable performance improvement without modifying the unpacking algorithm. Kenneth Almquist