ts@uwasa.fi (Timo Salmi LASK) (06/20/90)
In article <8762@crdgw1.crd.ge.com> davidsen@crdos1.UUCP (bill davidsen) writes: >In article <6782@amelia.nas.nasa.gov> roelofs@amelia.nas.nasa.gov (Ender Wiggin) writes: >| Lharc isn't exactly a speed demon under Unix, either (I haven't actually >| done a head-to-head speed test of the two, but they seem comparable). > > Since there is no PKZIP for UNIX, LHARC is a lot faster there. So are >ARC and ZOO. Phil has chosen not to compete in those systems. I've wondering about why. It doesn't make sound business sense, does it? ................................................................... Prof. Timo Salmi (Moderating at anon. ftp site 128.214.12.3) School of Business Studies, University of Vaasa, SF-65101, Finland Internet: ts@chyde.uwasa.fi Funet: gado::salmi Bitnet: salmi@finfun
ts@uwasa.fi (Timo Salmi LASK) (06/21/90)
In article <PVL3k4w162w@halcyon.wa.com> ralphs@halcyon.wa.com (Ralph Sims) writes: >davidsen@crdgw1.crd.ge.com (William E. Davidsen Jr) writes: > >> Since there is no PKZIP for UNIX, LHARC is a lot faster there. So are >> ARC and ZOO. Phil has chosen not to compete in those systems. > >I have heard of something called DEZIP (varying mileage) for unix. If >someone has source, I'd like to get it. The utilities to UNzip under Unix certainly exist (eg in directory /unix/ts at chyde.uwasa.fi) but what was meant here is that there is no ZIP, that is making the .zip files under Unix. ................................................................... Prof. Timo Salmi (Moderating at anon. ftp site 128.214.12.3) School of Business Studies, University of Vaasa, SF-65101, Finland Internet: ts@chyde.uwasa.fi Funet: gado::salmi Bitnet: salmi@finfun
ge@phoibos.cs.kun.nl (Ge Weijers) (06/27/90)
roelofs@amelia.nas.nasa.gov (Ender Wiggin) writes: >And the reason you haven't seen a zip program for Unix or VMS or whatever >is that it doesn't exist. You're welcome to write it, of course. :) I >took one look at Katz's description of the Implosion format and decided >cloning it was not for the faint of heart. But I suspect the literature >contains the basic algorithm for compression using Shannon-Fano trees; if >Katz himself had invented it, they'd probably be called "Katz trees" or >something similar, n'est-ce pas? Perhaps in Communications of the ACM... >any computer scientists/compression specialists out there know for sure? A good book (still not for the faintharted) is "Data Compression" by James Storer. published by Computer Science Press, I believe. I faintly remember something about Shannon-Fano trees in there. After reading it you'll certainly know why LHARC is slow. It uses 2 compression schemes, first a Lempel-Ziv variant which is much more complex than LZW, followed by dynamic Huffman coding on the high-order 6 bits of the 12-bit code. Where could I find the Implosion format, by the way? I'd like to have a peek at it. Ge' Weijers. Ge' Weijers Internet/UUCP: ge@cs.kun.nl Faculty of Mathematics and Computer Science, (uunet.uu.net!cs.kun.nl!ge) University of Nijmegen, Toernooiveld 1 tel. +3180612483 (UTC+1, 6525 ED Nijmegen, the Netherlands UTC+2 march/september
chad@csd4.csd.uwm.edu (D. Chadwick Gibbons) (07/10/90)
In article <1990Jun20.032819.23081@uwasa.fi> (Timo Salmi LASK) writes: |In article <8762@crdgw1.crd.ge.com> (bill davidsen) writes: |> Since there is no PKZIP for UNIX, LHARC is a lot faster there. So are |>ARC and ZOO. Phil has chosen not to compete in those systems. |I've wondering about why. It doesn't make sound business sense, |does it? A policy of PKWare inc. is not to release its sources. To effectively produce utilities for UNIX, you need just that--sources. Phil explains quite well how to perform the ZIP operations, it just takes some soul to bite the bullet and produce the code. As you know, plenty of un-zip utilities exist, just no create-zip utilities. -- D. Chadwick Gibbons, chad@csd4.csd.uwm.edu, ...!{rutgers,uunet}!uwm!uwmcsd4!chad
nulspace@eng.umd.edu (Michael Chang) (07/10/90)
>|In article <8762@crdgw1.crd.ge.com> (bill davidsen) writes: >|> Since there is no PKZIP for UNIX, LHARC is a lot faster there. So are >|>ARC and ZOO. Phil has chosen not to compete in those systems. Believe it or not, lharc is not faster at all on unix systems, at least between unix systems and PCs with sufficient hard drive space and RAM. I checked the source code, and it is the same for both DOS and Unix. I'm sure that lharc could be optimized to work faster on unix, I only wish someone would go do it. (I timed lharc on unix and lharc on an IBM PS/2 model 50, and the copy on the unix box (Vax3100) was able to finish compressing only about a second faster than the PS/2... out of a total compression time of about 55 secs.) nulspace@eng.umd.edu [ at work ] | "I've often been asked, and my replies are nulspace@wam.umd.edu [ at play ] | always in the same fashion; I hate tennis, | I hate it with a passion!" -Michael Chang
roelofs@amelia.nas.nasa.gov (Cave Newt) (07/10/90)
In article <4929@uwm.edu> chad@csd4.csd.uwm.edu (D. Chadwick Gibbons) writes: > A policy of PKWare inc. is not to release its sources. To >effectively produce utilities for UNIX, you need just that--sources. Phil >explains quite well how to perform the ZIP operations, it just takes some >soul to bite the bullet and produce the code. As you know, plenty of >un-zip utilities exist, just no create-zip utilities. As I've just recently been discussing with Ge' Weijers of the Netherlands, this "bullet" is more like an 80mm shell--duplicating the compression algorithm for Imploding is highly non-trivial, as they say in the mathematics business. And while Phil gives detailed algorithms for UNcompressing the various types of encoding, the compression end of things is much more sketchy. I don't imagine a PKZIP clone could be written in less than several weeks, and that's assuming full-time effort.... If, however, somebody would care to prove me wrong, I'll send 'em a Mrs. Fields chocolate chunk cookie. :) In article <8762@crdgw1.crd.ge.com> (bill davidsen) writes: > Since there is no PKZIP for UNIX, LHARC is a lot faster there. So are > ARC and ZOO. Phil has chosen not to compete in those systems. nulspace@eng.umd.edu (Michael Chang) writes: >Believe it or not, lharc is not faster at all on unix systems, at least >between unix systems and PCs with sufficient hard drive space and RAM. >I checked the source code, and it is the same for both DOS and Unix. I'm >sure that lharc could be optimized to work faster on unix, I only wish >someone would go do it. The point of Bill's posting was that LHARC wins over PKZIP under Unix, because PKZIP does not exist under Unix. Nobody was comparing times across operating systems--for one thing, the performance under Unix will depend a great deal on how many other users are on the system; and then, you can always toss LHARC in the background and go do something else under Unix, so in a sense it's infinitely faster than DOS. And best of all, Unix runs on Crays and DOS doesn't: I daresay LHARC and just about anything else you'd care to try would win hands down on an 8-processor Y-MP (assuming you could get the damn thing to compile correctly). Speaking of which: has anybody succeeded in making mods to LHARC to allow it to run under Unicos (64-bit long ints, 46-bit shorts)? If so, please send me e-mail. I've gotten it to compile, but something is breaking and I haven't yet discovered what. Many thanks... Greg
own@castle.ed.ac.uk (O Morgan) (07/10/90)
In article <4929@uwm.edu> chad@csd4.csd.uwm.edu (D. Chadwick Gibbons) writes: [stuff deleted] >soul to bite the bullet and produce the code. As you know, plenty of >un-zip utilities exist, just no create-zip utilities. I'm trying to get a version of UNZIP vor a VAX running VMS. Is there anyone prepared to provide me with source or an EXE to do this? -- ---------------------------------------------------------------------------- Olly Morgan **** Tel: (+44 31) 662 4395 **** E.Mail: O.Morgan@ed.ac.uk Edinburgh School of Agric. 42 South Oswald Rd, Edinburgh EH3 9NA, Scotland ----------------------------------------------------------------------------