[dahart]

Did the article use the wrong link? I used the link in the article. The C++ code from your link looks the same as what I saw.

Your bottom link shows the same data I see using the link in the article: the C++ is ~50% slower on spectral-norm.

I expect that the 12x outlier is because someone did something very non-optimal in C++.

[igouy]

Yes, the link grabbing seo claims the benchmarks game has something to say about Java and energy-efficient — in fact the benchmarks game does not measure energy use.

No, the link grabbing seo provides the correct source for Table 4 — "Source: Energy Efficiency across Programming Languages, SLE’17" — and google finds the article:

https://greenlab.di.uminho.pt/wp-content/uploads/2017/09/pap...

> looks the same

Please look again.

> the 12x outlier

    #include <pcre.h>
    vs
    #include <boost/regex.hpp>

[dahart]

Yeah so the 12x gap in regex-redux is measuring the speed of two completely different libraries, and obviously boost is what’s slow. It’s not a language difference, nor even primarily an issue with means vs medians. The issue with regex-redux is slightly more of comparing apples to oranges.

I assume you’re referring to regex-redux, but I was confused for a minute there because you linked directly to the C++ code for spectral-norm, not regex-redux, and spectral-norm doesn’t include a regex lib. I had to go looking around for the includes you’re talking about, and the Benchmarks-Game version has multiple C++ entries. There are C++ entries that use pcre, re2, and boost/regex. The C entries all use pcre except the winner, who uses pcre2.

> For a single outlier (regex-redux) there's a 12x difference between the measured times of the selected C and C++ programs.

BTW, I dont know exactly what they’re referring to there. The time ratio of the Benchmarks Game fastest C version to the slowest C++ version is over 16x. The ratios in the SLE paper of energy and run time are a bit lower than 12 but they also have only one sample, and it uses boost, so I don’t see why regex-redux with boost is useful in any perf or energy comparison other than to serve as a mild warning about using boost.

There happens to be a ratio of almost exactly 12x between the slowest C++ version (g++#3 boost) and the fastest C++ version (g++#6 - pcre2). That’s C++ vs C++. Maybe that’s what they were talking about, or maybe the perf numbers have changed out from under the commentary.

The ratio of times of the fastest C to the fastest C++ time with regex-redux is 1.4x and they both use pcre2. That seems like a more reasonable place to start.

[igouy]

> … not … primarily an issue with means vs medians

We're comparing averages, why would we bother so much about the cause of an outlier.

> you linked directly to the C++ code for spectral-norm

You had linked to the wrong C and C++ code for spectral-norm, I linked to the code that was actually used.

> The time ratio of the Benchmarks Game fastest C version to the slowest C++ version is over 16x.

Again, you seem to be looking at the wrong repo.

The authors of "Energy Efficiency across Programming Languages, SLE’17" provided this repo —

https://sites.google.com/view/energy-efficiency-languages

https://github.com/greensoftwarelab/Energy-Languages

[dahart]

I was talking about the Benchmarks game repo code. (But it doesn’t even matter because the SLE is equally bad.) And I was not comparing any averages, I was pointing out that use of boost is the entire reason the average is skewed and misleading. You seem to be misunderstanding my comments.

[igouy]

> I was talking about the benchmarks game repo code

Why? The benchmarks game doesn't show energy use of programs.

> use of boost is the entire reason

As you know, the fastest C++ program shown on the benchmarks game website uses pcre2.h.

[dahart]

In case you didn’t read the thread above or the comment I replied to, the subject had already veered away from energy use, with the comment by @tasubotadas, and my top comment was responding to that. I wasn’t ever commenting specifically on energy use per-se, I was commenting on the reason for the outlier, and responding to a specific comment about C++. That said, this just so happens to be completely relevant to both runtime and energy use. The benchmarks game and the SLE data both agree that using boost causes approximately an order of magnitude slowdown/energy increase to the regex-redux sample. I looked at both, and at your insistence I responded with SLE specific remarks. The lesson here is consider not using boost if you care about energy use, or about runtime. Is there a point you’re trying to make here?