On 7/25/15 8:19 AM, Johan Holmberg via Digitalmars-d wrote:
Hi!
I am trying to port a program I have written earlier to D. My previous
versions are in C++ and Python. I was hoping that a D version would be
similar in speed to the C++ version, rather than similar to the Python
version. But currently it isn't.
Part of the problem may be that I haven't learned the idiomatic way to
do things in D. One such thing is perhaps: how do I read large text
files in an efficient manner in D?
Currently I have created a little test-program that does the same job as
the UNIX-command "wc -lc", i.e. counting the number of lines and
characters in a file. The timings I get in different languages are:
D: 15s
C++: 1.1s
Python: 3.7s
Perl: 2.9s
I think this harkens back to the problem discussed here:
http://stackoverflow.com/questions/28922323/improving-line-wise-i-o-operations-in-d/29153508
As I discuss there, the performance bug has been fixed for 2.068. With
your code:
$ time wc -l <(repeat 1000000 echo hello)
1000000 /dev/fd/11
wc -l <(repeat 1000000 echo hello) 0.11s user 2.35s system 54% cpu
4.529 total
$ time ./test.d <(repeat 1000000 echo hello)
1000000 6000000 /dev/fd/11
./test.d <(repeat 1000000 echo hello) 0.73s user 1.76s system 64% cpu
3.870 total
The compilation was flag free (no -O -inline -release etc).
Andrei
