> On Sep 1, 2015, at 6:29 PM, David Carlson <david.carlson....@gmail.com> wrote: > > On 9/1/2015 5:13 PM, John Ralls wrote: >>> On Aug 28, 2015, at 8:17 PM, John Ralls <jra...@ceridwen.us> wrote: >>> >>> >>>> On Aug 28, 2015, at 6:43 AM, Geert Janssens <geert.gnuc...@kobaltwit.be> >>>> wrote: >>>> >>>> On Friday 28 August 2015 08:55:53 John Ralls wrote: >>>>> I’ve pushed a feature branch, single-price, to my Github repo >>>>> (https://github.com/jralls/gnucash <https://github.com/jralls/gnucash>) >>>>> which covers most of what we’ve >>>>> discussed here. I’m still wrestling with the math of how to sensibly >>>>> handle rounding itself, so what’s there still uses the hard-coded >>>>> 10^6 denom. The branch is from maint because I’d like to put these >>>>> changes in 2.6.8. >>>>> >>>>> The actual changes are explained in the commit notes. In my limited >>>>> testing it appears to work and to provide stability when doing >>>>> multiple transactions with the same exchange rate. Please test some >>>>> more; I’m sure I didn’t think of every possible variation. >>>>> >>>> Hi John, >>>> >>>> Thanks for your work on this. >>>> >>>> From my first tests and reading the code I have the following observations: >>>> >>>> - Let me start with a nit-pick: while reading through the commits I got >>>> confused by the return values of check_account and check_edit. They return >>>> TRUE if the check fails (that is when anything is not ok to continue with >>>> a transfer). From a distance that seems backwards. I usually expect a >>>> check function to return TRUE if all checks pass correctly. >>>> >>>> - Next I created a vendor bill, posted it and then paid it in a foreign >>>> currency. This also pops up the transfer dialog. I entered a price and >>>> continued. This added the price to the db (as expected). Next I remove the >>>> payment transaction (from the bank account in the foreign currency) and >>>> issue a new payment via the payment dialog, again in the same foreign >>>> currency. This time however, I enter a to amount directly (ensuring it >>>> would result in a completely different price). Check the price db and note >>>> the existing price hasn't changed. >>>> >>>> - The currencies I was playing with are € (from currency) and HKD (to >>>> currency). Before your changes my price db listed a HKD security EUR >>>> currency. On your branch the code now adds a EUR security in HKD currency. >>>> That change is fine in itself. I prefer your normalized way to store >>>> (currency) exchange rates in the db. The issue with this however is that >>>> F::Q won't return an exchange rate for the new price, while it did (and >>>> still does) for the old one. >>>> >>>>> As for the math, here’s the conundrum: I proposed earlier to base the >>>>> rounding on what would make a 1 scu change in the “to” commodity. The >>>>> problems with that idea are that it depends entirely on the amount in >>>>> the “from” commodity and that prices are often quoted in fractions of >>>>> a scu. For example, the Wall Street Journal website quotes the Yen at >>>>> 120.98 to the USD. The Yen’s scu is 1, and the change in the rate to >>>>> make a 1¥ change in the value is different if the USD amount is $10 >>>>> from what it would be if the amount was $1000. Carry that to its >>>>> illogical conclusion and we need infinite precision, and that’s >>>>> ignoring the fact that we need infinite precision to exactly >>>>> represent a lot of rational fractions, but since all the real money >>>>> systems use decimal math nowadays that’s not really germane. >>>>> >>>>> So I have a new proposal: If the commodities are both currencies, >>>>> store exchange rates in the direction where the rate > 1, set the >>>>> denominator to 1000, and round-half-up. The price retrieval code >>>>> already checks in both directions. If only one of the commodities is >>>>> a currency then it’s a price and we store it in the currency with the >>>>> denominator = the currency’s scu * 10000. >>>>> >>>> See above: the check in both directions is not reliable/borked. >>>> >>>>> That leaves commodity-commodity prices. The most common example in >>>>> modern life is stock-for-stock exchanges resulting from mergers or >>>>> spin-offs. These tend to be one-offs, so no rounding required. Barter >>>>> exchange, where one exchanges one commodity for another (e.g. two >>>>> bushels of corn for a cow), is similarly fractional rather than >>>>> decimal, so again not rounding is appropriate. The third case is the >>>>> problem: Bitcoin and similar pseudo-currencies. For maint I think >>>>> we’re going to have to leave those prices unrounded as well, but >>>>> perhaps for master we should consider creating a separate commodity >>>>> category so that users can create commodities that GnuCash treats as >>>>> currencies. >>>>> >>>> That looks like a very sensible proposal to me. >>> Geert, >>> >>> Thanks for testing. I agree that the check_foo() semantics are clumsy. I >>> did it that way to avoid negating the return value in the if conditional, >>> but in retrospect that would be clearer, so I’ll flip it. >>> >>> Roger that the checks aren’t reliably bidirectional. I’ll dig into that. I >>> hadn’t yet changed anything with regards to which direction prices are >>> recorded, at least not on purpose, so I’ll have to track that down too. >>> >>> I coded up the price-rounding algorithm on the flight back today and played >>> with it a little. I think it may need some adjustment. >> I’ve pushed more changes to single-price which I think address Geert’s >> comments and some tweaks to maximize significant digit preservation while >> keeping denominators <= 10E6 in most cases. Please test some more! >> >> Regards, >> John Ralls >> _______________________________________________ >> gnucash-devel mailing list >> gnucash-devel@gnucash.org >> https://lists.gnucash.org/mailman/listinfo/gnucash-devel > > I kind of lost track of how it is supposed to work for the user. If I > am slow to enter a buy or sell for a certain date, will GnuCash > overwrite a price that was downloaded earlier for the same security and > date or possibly manually entered earlier for that date? Sometimes I > create a buy or sell by duplicating a transaction that has the wrong > information then do several transaction saves as I am changing to the > correct accounts, amounts and date.
David, Quotes from F::Q are supposed to overwrite user entries for the day, but although F::Q is quite capable of retrieving historical quotes, GnuCash doesn’t use that facility. So if you create a transaction with a date_posted in the past and there isn’t already an F::Q quote for that day then the price generated from that transaction won’t get overwritten later on. On the other hand, if you do have an F::Q quote already on that day then the user price won’t get written to the price db. Umm, are you able to build from git? This code is currently on a feature branch so it isn’t going to get into the nightlies for you to test with otherwise. I think I understand the first test-case well enough to run tests myself, but I need more detail on the second (the duplicate-and-modify) one to test it. Regards, John Ralls _______________________________________________ gnucash-devel mailing list gnucash-devel@gnucash.org https://lists.gnucash.org/mailman/listinfo/gnucash-devel
