Obviously you can't accumulate cent by cent. You can't even safely accumulate by quarter. Epsilon is too large to do that. I calculate cumulative pnl using std::fma, then multiply AUM with that and round to cents. It's good enough for backtesting, and it shaves a bunch of seconds off the clock.
I see - I guess it's a financial modelling program or similar where the quantities don't represent precise values of money. I was imagining some kind of accounting-like app that would need to be reconciled with real-world balances.
