Here is a pull request that demonstrates a "better" handling of the exchange. Basically, conversion to the report currency should happen *after* the balance change has been computed, not before. If it happens before, it makes the historical, cumulative total's exchange-rate fluctuation during the budget period part of the result.
In the language of my last e-mail, this pull request computes "ES_12*X_1" (but perhaps it should be "ES_12*X_2"... to be discussed). https://github.com/Gnucash/gnucash/pull/1497 On Sun, Jan 8, 2023 at 9:34 AM ml enquirer <ml.hnel.227...@gmail.com> wrote: > Yes, it's cumulative, which is a problem I think. > > Let: > 0 indicate the opening of the book > 1 indicate the start of the budget period in question > 2 indicate the end of that period > S_i indicates the sum of transactions since 0 at marker i, in the currency > of the sub-account > P_i indicates the sum of transactions since 0 at marker i, in the currency > of the parent account > ES_ij indicates the sum of transactions during a period bounded by i and > j, in sub-account currency > X_i gives the exchange rate between sub-account and parent-account > > The trouble is that the report prints out: > > P_2 - P_1 > = S_2*X_2 - S_1*X_1 > = (S_1+ES_12) * X_2 - S_1 * X_1 > = ES_12 * X_2 + S_1( X_2 - X_1) > > My problem is that I only really care about the first term, that contains > ES_12. But as the years go by, S_1 >> ES_12, so the second term > increasingly dominates. This becomes particularly visible when X_2-X_1 is > significant, which has certainly been the case looking at GBP and EUR in > recent years ;) > > By the way, I agree that "ES_12*X_2" is a bit trivial, and it would be > nice to account for the variation of exchange rates during the year, but > that's a second-order effect compared to this bug. > > > > > To show this in the code: > > The "Actual" column in the budget report is populated by > "gnc:get-account-periodlist-actual-value" > > https://github.com/Gnucash/gnucash/blob/master/gnucash/report/reports/standard/budget.scm#L404 > > which just calls "gnc-budget-get-account-period-actual-value budget acct > period" > > https://github.com/Gnucash/gnucash/blob/master/gnucash/report/reports/standard/budget.scm#L313 > > which calls "gnc_budget_get_account_period_actual_value" > > https://github.com/Gnucash/gnucash/blob/master/libgnucash/engine/gnc-budget.cpp#L671gnc_budget_get_account_period_actual_value > > which calls "recurrenceGetAccountPeriodValue" > > https://github.com/Gnucash/gnucash/blob/master/libgnucash/engine/Recurrence.c#L421 > where the documentation says "@return the amount that an Account's value > changed between the beginning and end of the nth instance of the > Recurrence." > > The problem is that this does: > > https://github.com/Gnucash/gnucash/blob/master/libgnucash/engine/Account.cpp#L3992 > gnc_numeric b1, b2; > b1 = xaccAccountGetNoclosingBalanceAsOfDateInCurrency(acc, t1, NULL, > recurse); > b2 = xaccAccountGetNoclosingBalanceAsOfDateInCurrency(acc, t2, NULL, > recurse); > return gnc_numeric_sub(b2, b1, GNC_DENOM_AUTO, GNC_HOW_DENOM_FIXED); > _______________________________________________ gnucash-user mailing list gnucash-user@gnucash.org To update your subscription preferences or to unsubscribe: https://lists.gnucash.org/mailman/listinfo/gnucash-user ----- Please remember to CC this list on all your replies. You can do this by using Reply-To-List or Reply-All.
