elliot@alfred.UUCP (Elliot Dierksen) (07/07/90)
I posted this a while back, but I think my work news machine trashed it..
The solution to the cnews/16 bit compress is to copy NEWSBIN/batch/comp to
NEWSBIN/batch/comp16. Edit comp16 and remove the '-b 12' arguments to compress.
then change your batchparms and it's done!! I did this because I have a 1200
baud system that I feed and ANYTHING to cut down transmit time is worth it!!
EBD
--
Elliot Dierksen "I don't care if my lettuce has DDT on it,
as long as it's crisp!!" -- Jorma Kaukonen
Work) {att,codas}!candi!fang!ebd (407) 660-3377
Home) {peora,uunet,ucf-cs}!tarpit!alfred!elliot (407) 290-9744larry@nstar.uucp (Larry Snyder) (07/08/90)
elliot@alfred.UUCP (Elliot Dierksen) writes: >The solution to the cnews/16 bit compress is to copy NEWSBIN/batch/comp to >NEWSBIN/batch/comp16. Edit comp16 and remove the '-b 12' arguments to compress. But how much space does it save (difference beween 12 and 16 bit) verses time to compress (difference between 12 and 16 bit)? Just wondering? -- Larry Snyder, Northern Star Communications, Notre Dame, IN USA uucp: iuvax!ndmath!nstar!larry -or- larry@nstar Public Access Unix Site (219) 289-3745 / lots of files & free PEP feeds!
brad@looking.on.ca (Brad Templeton) (07/09/90)
In article <1990Jul08.130607.11867@nstar.uucp> larry@nstar.uucp (Larry Snyder) writes: >But how much space does it save (difference beween 12 and 16 bit) verses >time to compress (difference between 12 and 16 bit)? Just wondering? The saving can be pretty good - 10 to 15%, sometimes more, which works out to a lot over a long distance line. What's not intuitive is that on most 32 bit machines, 16 bit compress is NO SLOWER (and sometimes even times faster) than 12 and 13 bit compress. As Henry now admits, unless you know your destination can't decompress a 16 bit file, you should use the 16 bit compress. If you're on a 286 machine or other 16 bit-only machine, this is not true. The 13 bit compress (or 12 if you must) can be a lot faster. But let's face it, those dinosaurs are fading away. You can get a 386 32 bit motherboard for around $600 these days. -- Brad Templeton, ClariNet Communications Corp. -- Waterloo, Ontario 519/884-7473
elliot@alfred.UUCP (Elliot Dierksen) (07/09/90)
In article <1990Jul08.130607.11867@nstar.uucp>, larry@nstar.uucp (Larry Snyder) writes: |elliot@alfred.UUCP (Elliot Dierksen) writes: | |>The solution to the cnews/16 bit compress is to copy NEWSBIN/batch/comp to |>NEWSBIN/batch/comp16. Edit comp16 and remove the '-b 12' arguments to compress | |But how much space does it save (difference beween 12 and 16 bit) verses |time to compress (difference between 12 and 16 bit)? Just wondering? It saves about 10% I think... I haven't done any very careful study of it though. My machine is not heavily loaded and I feel that every byte I save when I feed a 1200 baud site is worth it. I suppose it's just a tradeoff that each site would have to make. Maybe when I finally get a Telebit, I won't worry about it. But until I break the 2400 baud barrier, 16 bits for me!! :-) EBD -- Elliot Dierksen "I don't care if my lettuce has DDT on it, as long as it's crisp!!" -- Jorma Kaukonen Work) {att,codas}!candi!fang!ebd (407) 660-3377 Home) {peora,uunet,ucf-cs}!tarpit!alfred!elliot (407) 290-9744
zeeff@b-tech.ann-arbor.mi.us (Jon Zeeff) (07/09/90)
Here are some figures: 16 bit compression: 7.2 seconds, 88827 bytes 12 bit compression: 8.4 seconds, 113879 bytes <- 16%/28% more. The test batch was 276K to start. Also figure the cpu time needed to send/receive the larger 12 bit compressed batch. Given the major win, 16 bit compression should be the default or at least strongly encouraged. Even 16 bit int machines can do 14 bit uncompression without slowdown. -- Jon Zeeff (NIC handle JZ) zeeff@b-tech.ann-arbor.mi.us
larry@nstar.uucp (Larry Snyder) (07/10/90)
zeeff@b-tech.ann-arbor.mi.us (Jon Zeeff) writes: >Here are some figures: >16 bit compression: 7.2 seconds, 88827 bytes >12 bit compression: 8.4 seconds, 113879 bytes <- 16%/28% more. >The test batch was 276K to start. Also figure the cpu time needed to >send/receive the larger 12 bit compressed batch. Then why does the news software default to 12 bit compression? -- Larry Snyder, Northern Star Communications, Notre Dame, IN USA uucp: iuvax!ndmath!nstar!larry -or- larry@nstar Public Access Unix Site (219) 289-3745 / lots of files & free PEP feeds!
henry@zoo.toronto.edu (Henry Spencer) (07/10/90)
In article <1990Jul09.170549.22946@nstar.uucp> larry@nstar.uucp (Larry Snyder) writes: >Then why does the news software default to 12 bit compression? There were some numbers in the distant past that suggested a different set of tradeoffs, and there is a problem with machines that can't handle anything bigger than 12. (The tricks that let an MSDOS box do up to 14 efficiently don't work on a pdp11, and yes Virginia, there are still some of those around.) Changes may be made. -- NFS is a wonderful advance: a Unix | Henry Spencer at U of Toronto Zoology filesystem with MSDOS semantics. :-( | henry@zoo.toronto.edu utzoo!henry
les@chinet.chi.il.us (Leslie Mikesell) (07/11/90)
In article <1990Jul10.153613.10971@zoo.toronto.edu> henry@zoo.toronto.edu (Henry Spencer) writes: >>Then why does the news software default to 12 bit compression? >There were some numbers in the distant past that suggested a different >set of tradeoffs, and there is a problem with machines that can't handle >anything bigger than 12. >Changes may be made. My experience with compress (not based on any serious testing or code checking) is that 16 bit compress consumes much more memory than 12 bit and is thus more likely to throw a machine into swapping/VM threashing when several processing are using it at the same time, even though there may not appear to be much difference in CPU consumption. Les Mikesell les@chinet.chi.il.us
brad@looking.on.ca (Brad Templeton) (07/13/90)
16 bit compress does indeed eat memory like a pig, BUT, if I remember correctly, the compress program that everybody uses eats up the same amount of memory no matter how many codes you tell it to use. It's a big hash table, and if you pick 12 bit (4096 codes) you still get a 400K table, it's just very sparse -- and thus has fewer collisions. To save memory with a 12 or 13 bit compress, you have to COMPILE it again with a hard limit on the number of bits. Using the option is not enough. -- Brad Templeton, ClariNet Communications Corp. -- Waterloo, Ontario 519/884-7473