>I'm guessing that your hardward does not implement IEEE 754 floating >point correctly. We've seen that sort of thing before, especially >with GCC. There are some options to GCC (which escape my memory right >now) that can force it to use strict IEEE 754 floating point rather >than its preferred, speedier but non-standard alternative.
What he's getting back is so far from correct, though, that I would tend to blame a run-of-the-mill bug rather than some point-of-detail. Non-IEEE floating point often sacrifices things like the distinctions between "Not-a-Number" and "Infinity," or the difference between positive and negative zero, and so on. Perhaps in some cases the rounding of the last bit is wrong. But no FP system should give results that are flat out wrong, especially when doing arithmetic. (I can see where series of operations involving exponents &c. might get way out-of-line but I don't think Sqlite is doing any of these things.) What he is getting back looks like Double.MaxVal... is there a divide-by-zero somewhere? That is the sort of thing that different FP specs will legimately handle differently. ________________________________________ From: sqlite-users-boun...@sqlite.org [sqlite-users-boun...@sqlite.org] On Behalf Of D. Richard Hipp [...@hwaci.com] Sent: Wednesday, November 04, 2009 9:26 AM To: General Discussion of SQLite Database Cc: Alexander Drozd Subject: Re: [sqlite] SQLite on PocketBook On Nov 4, 2009, at 4:53 AM, Alexander Drozd wrote: > > My name is Alexander. I am working on an open-source spaced- > repetition software project (http://code.google.com/p/pbanki/). My > software relies on SQLite library. I came across some bug-like > problems with running SQLite on a low-memory e-ink reader device. I > am very sorry to bother you, but I tried to submit my problem to > the bugtracker at the SQLite site, and for some reason anonymous > login failed. > > The problem appears at the point of reading real values from an > SQLite database. I created a simple database > > CREATE TABLE cards ( > text TEXT NOT NULL, > value REAL NOT NULL > ); > > I also tried to use NUMERIC and FLOAT instead of REAL. Then I > inserted a few values: > > INSERT INTO cards VALUES('second',100.1); > INSERT INTO cards VALUES('first', 100.0); > > Then I execute "select * from cards order by due" query with sample > code from http://www.sqlite.org/quickstart.html It works perfectly > when compiled on desktop computer, but fails on target device. The > device is PocketBook301+ (http://pocketbook.com.ua/). Unfortunately > their site does not have an English version. This device is based on > Samsung S3C2440 AL-40 CPU. It runs under open-source firmware called > pocketbookfree, that is based on Linux 2.6.18.2 armv4tl. > > The above query run on pocketbook returns corrupted values for > floats if they have a non-zero fractional part: > > text = first > val = 100.0 > > text = second > val = 1.90359837350824e+185 > > Sorting by columns containing float numbers also fails when > specified with ORDER BY. I am not sure whether this is an issue with > SQLite or with cross-compiler for PocketBook, but I would greatly > appreciate any suggestions on how to treat this problem. I'm guessing that your hardward does not implement IEEE 754 floating point correctly. We've seen that sort of thing before, especially with GCC. There are some options to GCC (which escape my memory right now) that can force it to use strict IEEE 754 floating point rather than its preferred, speedier but non-standard alternative. D. Richard Hipp d...@hwaci.com _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users The information contained in this e-mail is privileged and confidential information intended only for the use of the individual or entity named. If you are not the intended recipient, or the employee or agent responsible for delivering this message to the intended recipient, you are hereby notified that any disclosure, dissemination, distribution, or copying of this communication is strictly prohibited. If you have received this e-mail in error, please immediately notify the sender and delete any copies from your system. _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
