On Tue, 2019-12-10 at 15:50 -0700, Jim Finnerty wrote: > As a proof of concept, I hacked around a bit today to re-purpose one of the > bits of the Cost structure to mean "is_disabled" so that we can distinguish > 'disabled' from 'non-disabled' paths without making the Cost structure any > bigger. In fact, it's still a valid double. The obvious choice would have > been to re-purpose the sign bit, but I've had occasion to exploit negative > costs before so for this POC I used the high-order bit of the fractional > bits of the double. (see Wikipedia for double precision floating point for > the layout). > > The idea is to set a special bit when disable_cost is added to a cost. > Dedicating multiple bits instead of just 1 would be easily done, but as it > is we can accumulate many disable_costs without overflowing, so just > comparing the cost suffices.
Doesn't that rely on a specific implementation of double precision (IEEE)? I thought that we don't want to limit ourselves to platforms with IEEE floats. Yours, Laurenz Albe
