Am 21.03.2010 17:23, schrieb Martin Buchholz:
On Sun, Mar 21, 2010 at 04:28, Ulf Zibis<[email protected]> wrote:
On Sat, Mar 20, 2010 at 17:13, Ulf Zibis<[email protected]> wrote:
I don't think it's a performance problem in the real world.
Hm, if someone uses:
if (Character.isBMPCodePoint(codePoint))
...;
else if (Character.isSupplementaryCodePoint(codePoint)) // instead
isValidCodepoint()
...;
else
...;
he will loose up to 50 % performance as you can see on my benchmark on
isSuppCPAlaMartin().
Only if their data is full of supplementary characters.
Yes, but we dont't know anything about the purpose of code written there
in the world, so why not provide best performance or at least give a
hint in the docs, if it doesn't cost anything.
We don't usually put such performance information in the javadoc.
In class StringBuilder:
"Where possible, it is recommended that this class be used in preference to
StringBuffer as it will be faster under most implementations."
java.util.List:
Note that these operations may execute in time proportional to the index
value for some implementations (the LinkedList class, for example).
ByteBuffer#get(byte[],int,int):
In other words, an invocation of this method of the form
src.get(dst, off, len) has exactly the same effect as the loop
for (int i = off; i< off + len; i++)
dst[i] = src.get();
except that it first checks that there are sufficient bytes in this buffer
and it is potentially much more efficient.
In the above, the performance is a Raison d'être of the API,
that real users should consider when choosing API.
Oh, on parle français. Je l'aime beaucoup.
Anyway, even if isSupplementaryCodePoint() is used isolated, my code will
help JIT to use 2-byte shifted adressing and shorter 2-byte immediate value
for the compare, but yes, JIT should be able to catch that without this
help. But for that case, we could stay on the old implementations too for
isBMPCodePoint and is ValidCodePoint.
Again, performance with BMP characters is infinitely more important
than performance with supplementary characters.
You are right. But I can't see any reason, why the fast supplementary
version would harm the BMP performance.
-Ulf
