💊 CI failures summary and remediations

As of commit 4b15a86 (more details on the Dr. CI page):

• 2/2 failures possibly* introduced in this PR
  • 2/2 non-CircleCI failure(s)

Extra GitHub checks: 1 failed

• Failed: GitHub Actions - clang-tidy

ci.pytorch.org: 1 failed

• Failed: pr/pytorch-linux-xenial-rocm3.3-py3.6

@nikitaved can you review this? Also I'm getting a failure for XLA is that OK?

@ngimel @rgommers do have a look at the latest commit.

Dispatch needlessly compiles for all the dtypes, not just for floating point types. Fixing it however would require large copypaste, so in the interest of code clarity (but not binary size :-) ) I'm inclined to let it go as is, after you try @nikitaved's suggestion. Thoughts? If you come up with a clever way to avoid extra dispatch without copy paste, that would be awesome to, but if not, that's not a blocker.

I have introduced constexpr, but I don't think reintroducing unordered map will make things any faster. If you look at the following MWE, optimizations do not kick in even when the functors are declared constexpr when using the functor inside an unordered map:

#include <unordered_map>
#include <functional>
#include <iostream>
#include <chrono>

class F {
public:
  constexpr void operator() (int & a, int & b) const {
    a += b;
  }
};

int main(int argc, char* argv[]) {
  F fun;
  
  int a = atoi(argv[1]);
  int b = atoi(argv[2]);
  std::chrono::time_point<std::chrono::system_clock> start, stop;
  auto time = 0.0;
  using binary_t = std::function<void(int&, int&)>;
  std::unordered_map<int, binary_t> funcs;
  
  funcs[0] = fun;
  start = std::chrono::system_clock::now();
  for (long long i = 0; i < 10000000; ++i) {
    funcs[0](a, b);
  }
  stop = std::chrono::system_clock::now();
  
  std::cout << "time with unordered_map: " << std::chrono::duration_cast<std::chrono::nanoseconds>(stop - start).count() << std::endl;
  std::cout << "a: " << a << std::endl;
  a = 1;

  start = std::chrono::system_clock::now();
  for (long long i = 0; i < 10000000; ++i) {
    fun(a, b);
  }
  stop = std::chrono::system_clock::now();
  
  std::cout << "time without map: " << std::chrono::duration_cast<std::chrono::nanoseconds>(stop - start).count() << std::endl;
  std::cout << "a: " << a << std::endl;
}

Results:

time with unordered_map: 50887068
a: 30000001
time without map: 44
a: 30000001

New benchmark:
scatter-regression.py.csv.pdf

Is this ready? If so, can you please rebase so that we can get signal from CI, right now too many tests are failing.

CI errors are real.

@ngimel errors are fixed. Could you please have a look? The windows failures seem unrelated.

YEah, windows failures are unrelated, but can you please rebase so that we can get a signal from windows builds?

@ngimel updated and ready to merge.

@ngimel merged this pull request in 9ca4a46.