There are several reasons you should never (never ever) use SELECT * in production code: since you’re not giving your database any hints as to what you want, it will first need to check the table’s definition in order to determine the columns on that table. That lookup will cost some time – not much … Read more
Generally, iterrows should only be used in very, very specific cases. This is the general order of precedence for performance of various operations: vectorization using a custom Cython routine apply reductions that can be performed in Cython iteration in Python space itertuples iterrows updating an empty frame (e.g., using loc one-row-at-a-time) Using a custom Cython … Read more
I will start by saying that the power of Pandas and NumPy arrays is derived from high-performance vectorised calculations on numeric arrays.1 The entire point of vectorised calculations is to avoid Python-level loops by moving calculations to highly optimised C code and utilising contiguous memory blocks.2 Python-level loops Now we can look at some timings. … Read more
Why don’t you measure it using the timeit module? That way you can see whether it’s relevant to your application. OK, so I’ve just tried the following: import timeit statements=[“””\ try: b = 10/a except ZeroDivisionError: pass”””, “””\ if a: b = 10/a”””, “b = 10/a”] for a in (1,0): for s in statements: t … Read more
To enable all optimizations and disable all safety checks, compile your D program with the following DMD flags: -O -inline -release -noboundscheck EDIT: I’ve tried your programs with g++, dmd and gdc. dmd does lag behind, but gdc achieves performance very close to g++. The commandline I used was gdmd -O -release -inline (gdmd is … Read more
You can do this with ‘taskkill‘. With the /IM parameter, you can specify image names. Example: taskkill /im somecorporateprocess.exe You can also do this to ‘force‘ kill: Example: taskkill /f /im somecorporateprocess.exe Just add one line per process you want to kill, save it as a .bat file, and add in your startup directory. Problem … Read more
You’re actually doing pretty well to have a 51ms pause time with over 200Mb of live data. The system I work on has a larger max pause time with half that amount of live data. Your assumption is correct, the major GC pause time is directly proportional to the amount of live data, and unfortunately … Read more
I was able to mimic your results so I decompiled your program and there is a difference between Find and FirstOrDefault. First off here is the decompiled program. I made your data object an anonmyous data item just for compilation List<\u003C\u003Ef__AnonymousType0<string>> source = Enumerable.ToList(Enumerable.Select(Enumerable.Range(0, 1000000), i => { var local_0 = new { Name = … Read more
Your question made me curious, so I went ahead and ran some timings on the 3GHz in-order PowerPC CPU we work with. The test I ran was to make a simple 4d vector class with get/set functions class TestVec { float x,y,z,w; public: float GetX() { return x; } float SetX(float to) { return x=to; … Read more
I would EXPECT the first query to be quicker, mainly because you have an equivalence and an explicit JOIN. In my experience IN is a very slow operator, since SQL normally evaluates it as a series of WHERE clauses separated by “OR” (WHERE x=Y OR x=Z OR…). As with ALL THINGS SQL though, your mileage … Read more