I can reproduce your results on my machine with those options you write in your post. However, if I also enable link time optimization (I also pass the -flto flag to gcc 4.7.2), the results are identical: (I am compiling your original code, with container.push_back(Item());) $ g++ -std=c++11 -O3 -flto regr.cpp && perf stat -r … Read more
From the FxCop rule page on this: After you mark the methods as static, the compiler will emit non-virtual call sites to these members. Emitting non-virtual call sites will prevent a check at runtime for each call that ensures that the current object pointer is non-null. This can result in a measurable performance gain for … Read more
Using the following: g++ -O3 Time.cpp -I <MyBoost> ./a.out UseArray completed in 2.196 seconds UseVector completed in 4.412 seconds UseVectorPushBack completed in 8.017 seconds The whole thing completed in 14.626 seconds So array is twice as quick as vector. But after looking at the code in more detail this is expected; as you run across … Read more
First, always use the latest version of PostgreSQL. Performance improvements are always coming, so you’re probably wasting your time if you’re tuning an old version. For example, PostgreSQL 9.2 significantly improves the speed of TRUNCATE and of course adds index-only scans. Even minor releases should always be followed; see the version policy. Don’ts Do NOT … Read more
auto can aid performance by avoiding silent implicit conversions. An example I find compelling is the following. std::map<Key, Val> m; // … for (std::pair<Key, Val> const& item : m) { // do stuff } See the bug? Here we are, thinking we’re elegantly taking every item in the map by const reference and using the … Read more
Very easy to measure… In a small number of tight-loop processing code where I know the length is fixed I use arrays for that extra tiny bit of micro-optimisation; arrays can be marginally faster if you use the indexer / for form – but IIRC believe it depends on the type of data in the … Read more
The pattern that you need to follow depends on your use case. First: You might have a situation where you need to add event listener during the initial mount and clean them up at unmount and another case where a particular listener needs to be cleaned up and re-added on a prop change. In such … Read more
I took hhafez code and added a memory test: private static void test() { Runtime runtime = Runtime.getRuntime(); long memory; … memory = runtime.freeMemory(); // for loop code memory = memory-runtime.freeMemory(); I run this separately for each approach, the ‘+’ operator, String.format and StringBuilder (calling toString()), so the memory used will not be affected by … Read more
There’s no extra Intermediate language (IL) code for the var keyword: the resulting IL should be identical for non-anonymous types. If the compiler can’t create that IL because it can’t figure out what type you intended to use, you’ll get a compiler error. The only trick is that var will infer an exact type where … Read more
this may not be accurate but its close enough for me long size = 0; object o = new object(); using (Stream s = new MemoryStream()) { BinaryFormatter formatter = new BinaryFormatter(); formatter.Serialize(s, o); size = s.Length; }