[GNC] Decimal Precision Entering Mutual Fund Transactions

[John Ralls]

> On Oct 24, 2021, at 2:24 PM, Robin Chattopadhyay <robinraymn at gmail.com> wrote:
> 
> Hi all-
> 
> SETUP:
> Version 4.8 (plus the commit to fix Bug 798327)
> OS: Ubuntu 20.04 LTS
> 
> SCENARIO:
> My wife recently started a new job where the 401k provider maintains the
> mutual fund positions at nine decimal places (and the price is two decimal
> places precision). I set up the security with the fraction traded set to
> 1*10^9, I set up the account's fraction traded to 'Use Commodity Value'
> 
> When entering a transaction into the register directly with the full nine
> decimal places, GnuCash cuts off the last digit and appears to only save up
> to the 8th significant digit thus introducing a small (but annoying)
> position difference between my books and the recordkeeper.
> 
> However, if I import the transactions from the OFX file downloaded from the
> recordkeeper's website, the full nine digits are imported and displayed in
> the register.
> 
> Another related item is that the share amount displayed changes from 9
> digits to 8 digits back to 9 when moving between transactions. For example,
> a transaction with 4.008105604 shares shows 4.0081056 as long as that
> transaction has the focus.
> 
> The workaround for now appears to only import transactions from the OFX
> file, which is fine but it does seem weird to have this inconsistent
> experience.
> 
> I glanced through Register-related bugs but I didn't see anything that
> jumped out at me as an open existing bug that would explain this behavior.
> (I'll concede that my search may have been lacking because previous
> discussion on this list related to precision and integer math have gone
> over my head)

I can replicate that. The truncation happens when one tabs out of the field, suggesting an off-by-one clamp the register somewhere.

Regards,
John Ralls