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You can write C in C++ but it won't be idiomatic C++. I've seen plenty of experienced "C++" developers that have no idea what is "shared_ptr".

dahart 3y ago
True partly because shared_ptr is a relatively new language feature; I’ve been locked to a ~decade-old C++ compiler for most of my professional career, and so has everyone I know, just because support for a current compiler across platforms at any given time has been historically so spotty. It seems to be improving at the moment. > it won’t be idiomatic I just looked at the first example: C: https://benchmarksgame-team.pages.debian.net/benchmarksgame/program/spectralnorm-gcc-3.html https://benchmarksgame-team.pages.debian.net/benchmarksgame/... C++: https://benchmarksgame-team.pages.debian.net/benchmarksgame/program/spectralnorm-gpp-8.html https://benchmarksgame-team.pages.debian.net/benchmarksgame/... The C++ doesn’t use shared_ptr or STL or anything, and isn’t that far from the C code, but it isn’t that close either. I wonder if it’s OMP configuration that’s causing it to be slower, or maybe just instruction cache or something since the C++ is larger. The results say this one has C++ going 50% slower. I’m a little skeptical it’s the compiler’s or the language’s fault. I’d speculate it might have more to do with how the program is written.
- dahart 3y ago
  Oh it does too use STL, guess I’m blind. That could be part of the reason it’s slower.
- igouy 3y ago
  You seem to be looking at the wrong source code. The "Energy Efficiency across Programming Languages, SLE’17"authors provided this repo — https://github.com/greensoftwarelab/Energy-Languages/blob/master/C/spectral-norm/spectralnorm.gcc-4.c https://github.com/greensoftwarelab/Energy-Languages/blob/ma... https://github.com/greensoftwarelab/Energy-Languages/tree/master/C%2B%2B/spectral-norm https://github.com/greensoftwarelab/Energy-Languages/tree/ma... For a single outlier (regex-redux) there's a 12x difference between the measured times of the selected C and C++ programs. Even so, that mostly messes up the results because the arithmetic mean is used rather than the median. https://benchmarksgame-team.pages.debian.net/benchmarksgame/sometimes-people-just-make-up-stuff.html#averages https://benchmarksgame-team.pages.debian.net/benchmarksgame/...
  - dahart 3y ago
    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 3y ago
      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/paperSLE.pdf 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 3y ago
        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.

dahart 3y ago

True partly because shared_ptr is a relatively new language feature; I’ve been locked to a ~decade-old C++ compiler for most of my professional career, and so has everyone I know, just because support for a current compiler across platforms at any given time has been historically so spotty. It seems to be improving at the moment. > it won’t be idiomatic I just looked at the first example: C: https://benchmarksgame-team.pages.debian.net/benchmarksgame/program/spectralnorm-gcc-3.html https://benchmarksgame-team.pages.debian.net/benchmarksgame/... C++: https://benchmarksgame-team.pages.debian.net/benchmarksgame/program/spectralnorm-gpp-8.html https://benchmarksgame-team.pages.debian.net/benchmarksgame/... The C++ doesn’t use shared_ptr or STL or anything, and isn’t that far from the C code, but it isn’t that close either. I wonder if it’s OMP configuration that’s causing it to be slower, or maybe just instruction cache or something since the C++ is larger. The results say this one has C++ going 50% slower. I’m a little skeptical it’s the compiler’s or the language’s fault. I’d speculate it might have more to do with how the program is written.

dahart 3y ago
Oh it does too use STL, guess I’m blind. That could be part of the reason it’s slower.
igouy 3y ago
You seem to be looking at the wrong source code. The "Energy Efficiency across Programming Languages, SLE’17"authors provided this repo — https://github.com/greensoftwarelab/Energy-Languages/blob/master/C/spectral-norm/spectralnorm.gcc-4.c https://github.com/greensoftwarelab/Energy-Languages/blob/ma... https://github.com/greensoftwarelab/Energy-Languages/tree/master/C%2B%2B/spectral-norm https://github.com/greensoftwarelab/Energy-Languages/tree/ma... For a single outlier (regex-redux) there's a 12x difference between the measured times of the selected C and C++ programs. Even so, that mostly messes up the results because the arithmetic mean is used rather than the median. https://benchmarksgame-team.pages.debian.net/benchmarksgame/sometimes-people-just-make-up-stuff.html#averages https://benchmarksgame-team.pages.debian.net/benchmarksgame/...
- dahart 3y ago
  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 3y ago
    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/paperSLE.pdf 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 3y ago
      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.