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Motion P1788/M0009.01_ExactDotProduct: NO



Reluctantly, after hearing the arguments of recent days, I change my vote to NO. The argument is finely balanced but my position on YES is now the same as Baker's, so I repeat that below.

A change that would make me vote YES:
I would vote "YES" if, instead of an exact dot product, we mandated
a dot product that is correctly rounded to the working precision.
In the case of point inputs, this would mean that round-down,
round-up, and round to nearest would be supported.  For instance,
in round to nearest, it would mean the nearest floating point
number to the exact dot product.

Note that this change would not preclude an implementer from supplying
an exact dot product, and that would be one way the requirement
could be achieved.  However, a correctly rounded dot product
both ensures cross-platform reproducibility and avoids certain
efficiency or difficulty issues in implementation.


John