On Sun, 2014-06-29 at 14:11 -0400, Jay Lozier wrote: > On 06/29/2014 12:53 PM, Terrence Enger wrote: > > Hi, all. > > > > I have just, for the first time that I remember, changed a confirmed bug > > report to a request for enhancement. I would like confirmation or > > correction of my judgement. > > > > The report is fdo#80638 "Incorrect SUM with decimal numbers" > > <https://bugs.freedesktop.org/show_bug.cgi?id=80638>. My thought is > > that Calc simply does not do decimal numbers. > > > > Thanks for your attention, > > Terry. > Hi, > > This is not an LO bug. I get the exact same result with a Python script, > a Ruby script, and Calligra Sheets. > > It is a problem with internal representation of decimal numbers in any > computer system. This is a well known problem in scientific > computing/numerical analysis.
I think I hear a distant voice, echoing down the decades, sayting "truncation error". <rant> The PC world tends to accept this problem as inevitable. However, the larger IBM systems going back to System/360 and other systems inspired by it have offered decimal arithmetic. This, too, has its "funnies", but the problems tend to manifest themselves in high-order digits, and so are often less subtle. </rant> > > Also, reordering the addition produced different precisions. I think the > correct numerical analysis term for this is precision referring to how > closely the actual value is to the true value. > > I would close this report with the note this is not a problem specific > to LO or any other spreadsheet. All spreadsheets will produce similar > results depending on the specifics of how real numbers are handled by > the underlying OS/CPU. The computers handle real numbers well enough they can fool the unwary into thinking that the computers' real numbers are like a mathematician's real numbers. It just ain't so, of course: the computer's real numbers are a finite subset of the mathematician's rational numbers. I cannot imagine what a good fix for the problem would be. And to change the result of a calculation, even a wrong result, is likely to break somebody's workflow. One possibility is to introduce a new function, call it betterSum perhaps, which accumulates the addends in order of increasing absolute value. This would not change the behaviour of existing spreadsheets. I do not expect that this would be worth the effort. So, yes, I think I shall close the report NOTABUG. (But you can tell that I am greatly tempted by NOTOURBUG, can't you?) > > Jay > > Thank you, Jay, for helping me to this decision. Terry, _______________________________________________ List Name: Libreoffice-qa mailing list Mail address: Libreoffice-qa@lists.freedesktop.org Change settings: http://lists.freedesktop.org/mailman/listinfo/libreoffice-qa Problems? http://www.libreoffice.org/get-help/mailing-lists/how-to-unsubscribe/ Posting guidelines + more: http://wiki.documentfoundation.org/Netiquette List archive: http://lists.freedesktop.org/archives/libreoffice-qa/
