On Sun, Jul 26, 2015 at 5:36 PM, Andrei Alexandrescu via Digitalmars-d <digitalmars-d@puremagic.com> wrote:

On 7/26/15 10:35 AM, Johan Holmberg via Digitalmars-d wrote:

On Sat, Jul 25, 2015 at 10:12 PM, Andrei Alexandrescu via Digitalmars-d
<digitalmars-d@puremagic.com <mailto:digitalmars-d@puremagic.com>> wrote:

On 7/25/15 1:53 PM, Johan Holmberg via Digitalmars-d wrote:
[...]
I download a dmd 2.068 beta, and re-tried with my input file:
now the D
program takes 1.6s (a 10x improvement).

Great, though it still seems to be behind the C++ version, which is
a bummer. -- Andrei
[... linux numbers removed ...]

I think we should investigate this and bring performance to par. Anyone interested? -- Andrei

Back on MacOS again, I thought I should try to run "Instruments" on my program. I'm not familiar with the DMD source code, but I did the following:

- downloaded the DMD source from Github + built it

- rebuilt my program with this dmd

- used Instruments (the MacOS profiler) on my program

Two things showed up in Instruments that seemed suspicious, both in "stdio.d":

1) calls to "__tls_get_addr" inside readlnImpl" (taking 0.25s out of the total 1.69s according to Instruments). I added "__gshared" to the static variables "lineptr" and "n" to see if it had any effect (see below for results).

2) calls to "std.algorithm.endsWith" inside File.ByLine.Impl.popFront (taking 0.10s according to Intruments). I replaced it with a simpler test using inline code.

The timings running my program normally (not using Instruments now), became as follows with the different versions of dmd:

dmd unmodified: 1.59s

dmd with change 1): 1.33s

dmd with change 1+2): 1.22s

C++ using <stdio.h>: 1.13s (for comparison)

My changes to dmd are of course not correct, but my program still works as before at least. If 1) and 2) could be changed "the right way" the difference to the C++ program would be much smaller on MacOS (I haven't looked further into the Linux results).

Does this help getting forward?

/johan