On Friday, 20 March 2015 at 05:17:11 UTC, Walter Bright wrote:
On 3/19/2015 9:59 AM, "Ola Fosheim =?UTF-8?B?R3LDuHN0YWQi?=
<[email protected]>" 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...
Sigh. The Python version:
-----------
import sys
if __name__ == "__main__":
if (len(sys.argv) < 2):
sys.exit()
infile = open(sys.argv[1])
linect = 0
for line in infile:
linect += 1
print "There are %d lines" % linect
----------
does not allocate memory. The splitLines() version:
[...] cutted
Of course it does allocate memory.
Python's "for...in" makes use of iterators and generators,
already there you have some allocations going around.
Not only that, there is one string being allocated for each line
in the file being read, even if it isn't used.
Not counting the whole minor allocations going on.
--
Paulo
