On Sun, 3 Nov 2013 10:30:40 +0000, Sean Owen wrote:
On Sun, Nov 3, 2013 at 4:17 AM, Ted Dunning <ted.dunn...@gmail.com>
wrote:
Does this actually matter after the JIT takes hold? And if the JIT
doesn't
care to optimize this away, does it even matter?
Unclear. There aren't hard guarantees about what the JIT does, but
transformations like this should be easy and local. Doesn't optimize
!= doesn't matter though. The 2D load/store is harder to match, and
there's one place it matters a bit in EigenDecomposition. I always
figure it helps to write an increment/decrement as what it is -- all
the better that it can't hurt speed.
These are all fairly trivial. The motivation was more from
consistency
in most cases, with an occasional small runtime benefit. I was more
wondering if, it were just a matter of pressing a button, it would be
desirable to zap a lot like this. I think the right approach is
indeed
to propose a couple targeted changes and move on.
Standardization is the key concept. A worthy goal even it brings zero
performance improvement.
Others that might be of interest, as food for thought:
- Standardizing literals? like saying "0.3" instead of ".3" or ".3d",
If the number is like 0.3, it probably has to be declared as a
"private static final" field with a telling name.
A case that occurs often is "zero" (as "double").
I prefer "0d".
and writing "2L" not "2l" since the latter looks like "21"
Same here.
For zero as long, I'm for "0L".
- Using log1p() for computing log(1+p) with a tiny bit more accuracy
in a few places
Certainly.
Best,
Gilles
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