Re: [PATCH] utils: Reduce chance of rounding inaccuracy in qemu_strtosz.

[Richard Henderson]

On 3/11/21 2:07 PM, Eric Blake wrote:
> +        /*
> +         * Add in a fudge-factor (2^53 when double is IEEE format) for
> +         * all scales less than P (2^50), so that things like
> +         * 12.345M with unit 1000 produce 12345000 instead of
> +         * 12344999.
> +         */
> +        if (mul > 1e49) {

The comment says less than, the code says greater than.


> An alternative patch might be writing (uint64_t)(fraction * mul + 0.5)
> (that is, introduce the fudge factor after the multiplication instead
> of before).  Preferences?

I think I would prefer this, or for further rounding error reduction, 
fma(fraction, mul, 0.5).


r~