[This message was posted by Rolf Andersson of Pantor Engineering <[EMAIL PROTECTED]> to the "FAST Protocol" discussion forum at http://fixprotocol.org/discuss/46. You can reply to it on-line at http://fixprotocol.org/discuss/read/3858317c - PLEASE DO NOT REPLY BY MAIL.]
Maybe delta? Consider the following scenario. You have 15000 ISIN-codes. (index 1-127 => 1 byte, index 128-16383 => 2 bytes) So, most of the time you will use 2 bytes to represent the index. Now let's assume some locality in the index values used. Given that two values are within -64 -- +63 apart, you would get a one byte index delta instead of a two byte index value. The back-side of this setup is that deltas <-8192 and >8191 will need 3 bytes to be represented (because deltas are signed). Anyway, we will most probably find use for the operators in the map case as well. /Rolf > The template syntax should probably be the other way around: > > <string name="Symbol"> <map/> </string> > > meaning that map would be used in the same way as other field operators. > > Other things to consider is whether the map operator should > utilize a bit in the presence map. If it should use a bit, there > are a number of options. > > Either we use the bit to indicate declaration (instead of using a > special zero key), or we could combine the map operator with some > other operator semantics. > > In the latter case, the most straightforawd choice would probably > be to add copy semantics. However, it might be a bit contradictory > since if copy was a good candidate for the usage pattern in the > first place, it could turn out that adding the map functionality > was of little value. > > /David [You can unsubscribe from this discussion group by sending a message to mailto:[EMAIL PROTECTED] --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Financial Information eXchange" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/FIX-Protocol?hl=en -~----------~----~----~----~------~----~------~--~---
