On 3/19/15 10:40 AM, weaselcat wrote:
On Thursday, 19 March 2015 at 16:59:36 UTC, Ola Fosheim Grøstad wrote:
On Thursday, 19 March 2015 at 00:42:51 UTC, weaselcat wrote:
On Wednesday, 18 March 2015 at 12:59:17 UTC, bearophile wrote:
High level constructs in D are often slower than low-level code, so
in some cases you don't want to use them.
I actually found that LDC does an _amazing_ job of optimizing high
level constructs and converting "low level" code to higher level
functional code resulted in minor speedups in a lot of cases.
(Other performance benefits include the algorithm primitives being
extensively optimized in phobos.)
If the code/compiler generates suboptimal code in the first place then
improvements can be somewhat random. But if you write code with good
cache locality, filling the pipeline properly then there is no
alternative to going low level.
Btw, take a look at this:
http://stackoverflow.com/questions/28922323/improving-line-wise-i-o-operations-in-d
That's really bad marketing...
python:
time python2 wc.py enwiki-latest-pages-articles1.xml-p000000010p000010000
There are 1245473 lines
python2 wc.py enwiki-latest-pages-articles1.xml-p000000010p000010000
0.21s user 0.08s system 99% cpu 0.294 total
wc -l:
time wc -l enwiki-latest-pages-articles1.xml-p000000010p000010000
1245472 enwiki-latest-pages-articles1.xml-p000000010p000010000
wc -l enwiki-latest-pages-articles1.xml-p000000010p000010000 0.05s user
0.02s system 96% cpu 0.072 total
iterative version:
ldc -O5 -inline -release -boundscheck=off wc.d
time ./wc
There are 1245473 lines.
./wc enwiki-latest-pages-articles1.xml-p000000010p000010000 0.59s user
0.07s system 99% cpu 0.661 total
functional version:
writeln("There are ",
(cast(string)read(args[1])).splitter('\n').array.length, " lines.");
ldc -O5 -inline -release -boundscheck=off wc.d
time ./wc enwiki-latest-pages-articles1.xml-p000000010p000010000
There are 1245473 lines.
./wc enwiki-latest-pages-articles1.xml-p000000010p000010000 0.04s user
0.08s system 98% cpu 0.125 total
You may want to answer there, not here. I've also posted a response.
Andrei
