This review came up a year ago. <-1> is an append on the attribute level. <1,-1> is not as effecient as it doesn't know that the record is only one attribute long.
I don't know about U2, but if I detect a very large appended item, say over 30,000 attributes, I use a DIM array and a counter. This is for exporting HTML or large text files. If you have OSWRITESEQ (I forget what it's called), you can write appendingly. After all, what's the next step after building your large <-1> array. My 1 cent Mark Johnson ----- Original Message ----- From: "Womack, Adrian" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Thursday, March 08, 2007 10:40 PM Subject: RE: [U2] old dog, new tricks > This is more of an "old trick". > > The reason that <-1> is so much faster is because using <-1> just > appends to an already existing string in memory. Where using <n> will > cause an entirely new string to be created and the old one thrown away > (to be eventually garbage collected). The process gets slower & slower > as each successive string becomes larger and larger. > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Scott Ballinger > Sent: Friday, 9 March 2007 11:10 AM > To: [email protected] > Subject: [U2] old dog, new tricks > > Perhaps this is not a revelation to many of you, but I did not realize > how _much_ faster it is to append items to a large array using <-1> vs. > an incrementing count, e.g. <n>. I was trying to speed up a program that > builds large arrays, and changed to the <-1> style append. > > Wow [can I say that? this is a linux box, not MS-Vista; is "wow" > copyrighted yet?], huge improvement! (UV 10.1.4 pick flavor, intel cpu). > Of course, when using <-1> you need to check for nulls as appropriate, > but even adding after adding code to test for and handle appending a > null attribute this is still way faster. > > Also, I think UV is optimized for AMs vs VMs, so that it pays to CONVERT > @VM TO @AM IN XXX, do your thing, then CONVERT @VM TO @AM IN XXX back > when done if you need VMs. > > /Scott Ballinger > Pareto Corporation > Edmonds WA USA > 206 713 6006 > > > > > > DISCLAIMER: > Disclaimer. This e-mail is private and confidential. If you are not the intended recipient, please advise us by return e-mail immediately, and delete the e-mail and any attachments without using or disclosing the contents in any way. The views expressed in this e-mail are those of the author, and do not represent those of this company unless this is clearly indicated. You should scan this e-mail and any attachments for viruses. This company accepts no liability for any direct or indirect damage or loss resulting from the use of any attachments to this e-mail. > ------- > u2-users mailing list > [email protected] > To unsubscribe please visit http://listserver.u2ug.org/ ------- u2-users mailing list [email protected] To unsubscribe please visit http://listserver.u2ug.org/
