On 8/29/22 19:07, Jeff Law via Gcc-patches wrote:
One of the more interesting ones is to try to limit the range of the
input to the trigonometric functions - that way you could use ones
without any argument reduction phase ...
The difficult part is that most of the trig stuff is in libraries, so we
don't have visibility into the full range.
What we do sometimes have is knowledge that the special values are
already handled which allows us to do things like automatically
transform a division into estimation + NR correction steps (atan2).
I guess we could do specialization based on the input range. So rather
than calling "sin" we could call a special one that didn't have the
reduction step when we know the input value is in a sensible range.
Exactly. It's probably not that hard to have sin/cos/tan with a special
entry point that foregoes the whole argument reduction step.
In every weather forecast, you have to compute the local solar height
(to get the effects of solar radiation correct) every time step, in
every grid point.
You *know* that angle is between 0 and 90 degrees, as are all the angles
that go into that computation (latitude, longitude (and time [hour of
the day, day of the year]).
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