The answer is probably in app-utils/calculation. All of that was probably written before Guile grew a rational number class and I think that GncNumerics get converted to doubles before being passed to the interest functions. That would pretty much guarantee rounding issues.
Regards, John Ralls > On Jan 8, 2019, at 5:46 PM, Christopher Lam <christopher....@gmail.com> wrote: > > Well the SCM has numerous references to "round" and "rounding errors" so it's > to be expected. > > Please file a bug with example numbers, and hopefully these errors may be > fixed. > > On 9/1/19 7:35 am, David Carlson wrote: >> John, >> >> Thanks for the reference. Alas, I will need to do some homework to >> properly read SCM. There must still be some sort of rounding issue >> creeping in if the Scheduled Transaction SLR sometimes generates an >> imbalance from ppmt = pmt - ipmt. >> >> David C >> >> On Tue, Jan 8, 2019 at 3:44 PM John Ralls <jra...@ceridwen.us> wrote: >> >>> The thee functions are defined in >>> https://github.com/Gnucash/gnucash/blob/maint/libgnucash/app-utils/fin.scm, >>> prefixed with gnc: (so gnc:ipmt etc.). >>> >>> At line 41ff you'll see that ppmt = pmt - ipmt. >>> >>> Regards, >>> John Ralls >>> >>> >>>> On Jan 8, 2019, at 12:48 PM, David Carlson <david.carlson....@gmail.com> >>> wrote: >>>> My point is that the equations are defined by the assistant, and I think >>> that they can be expressed in a form that concentrates all the errors into >>> one line where a simple rounding would not generate a problem where the >>> parts do not add up to 100%. Granted, the errors may sometimes cause >>> inaccurate results, but they would not add the imbalance line to the >>> transaction. >>>> The current equations are three evaluations called pmt(numbers), >>> ppmt(numbers) and ipmt(numbers) with no clue how they are actually >>> evaluated. >>>> Apparently pmt is not always the sum of ppmt and ipmt. when rounding >>> happens. If ipmt were expressed as pmt-ppmt, there would be no imbalance, >>> but one of the other two ways to express all three may be less likely to >>> generate inaccurate results. >>>> David C >>>> >>>> On Mon, Jan 7, 2019 at 10:19 PM John Ralls <jra...@ceridwen.us> wrote: >>>> >>>> >>>>> On Jan 7, 2019, at 3:14 PM, David Carlson <david.carlson....@gmail.com> >>> wrote: >>>>> I just had a scheduled transaction that was set up by the loan/mortgage >>>>> repayment assistant appear with 0.01 Imbalance-USD. >>>>> >>>>> I would think that GnuCash should have an accuracy method that would >>>>> prevent this from happening. Is this a bug? >>>>> >>>>> I am using GnuCash 2.6.17 in Ubuntu 16.04 today. >>>> The accuracy method is what created the imbalance entry. ;-) >>>> >>>> There’s nothing in the SX system to pre-instantiate future scheduled >>> transactions and ensure that they’re balanced. What would you have the >>> check function do if it found an imbalanced case? How would you handle >>> variables whose values are set by the user in the SLR dialog? >>>> Regards, >>>> John Ralls >>>> >>> >> _______________________________________________ >> gnucash-user mailing list >> gnucash-user@gnucash.org >> To update your subscription preferences or to unsubscribe: >> https://lists.gnucash.org/mailman/listinfo/gnucash-user >> If you are using Nabble or Gmane, please see >> https://wiki.gnucash.org/wiki/Mailing_Lists for more information. >> ----- >> Please remember to CC this list on all your replies. >> You can do this by using Reply-To-List or Reply-All. > _______________________________________________ > gnucash-user mailing list > gnucash-user@gnucash.org > To update your subscription preferences or to unsubscribe: > https://lists.gnucash.org/mailman/listinfo/gnucash-user > If you are using Nabble or Gmane, please see > https://wiki.gnucash.org/wiki/Mailing_Lists for more information. > ----- > Please remember to CC this list on all your replies. > You can do this by using Reply-To-List or Reply-All. _______________________________________________ gnucash-user mailing list gnucash-user@gnucash.org To update your subscription preferences or to unsubscribe: https://lists.gnucash.org/mailman/listinfo/gnucash-user If you are using Nabble or Gmane, please see https://wiki.gnucash.org/wiki/Mailing_Lists for more information. ----- Please remember to CC this list on all your replies. You can do this by using Reply-To-List or Reply-All.
