What Process is using all of my disk IO [closed]
You’re looking for iotop (assuming you’ve got kernel >2.6.20 and Python 2.5). Failing that, you’re looking into hooking into the filesystem. I recommend the former.
performance
HashSet versus Dictionary w.r.t searching time to find if an item exists
HashSet vs List vs Dictionary performance test, taken from here. Add 1000000 objects (without checking duplicates) Contains check for half the objects of a collection of 10000 Remove half the objects of a collection of 10000
How to overload std::swap()
The right way to overload std::swap‘s implemention (aka specializing it), is to write it in the same namespace as what you’re swapping, so that it can be found via argument-dependent lookup (ADL). One particularly easy thing to do is: class X { // … friend void swap(X& a, X& b) { using std::swap; // bring … Read more
Is there any benefit to upgrading Java 7 compiled code to Java 8?
If I understand the question correctly, you want to know if the bytecode produced by javac will be “better” in Java 8 than in Java 7. The answer is probably not, they constantly fix bugs in the compiler and that sometimes leads to more efficient bytecode. But you will not see any significant speedup from … Read more
Efficient evaluation of a function at every cell of a NumPy array
You could just vectorize the function and then apply it directly to a Numpy array each time you need it: import numpy as np def f(x): return x * x + 3 * x – 2 if x > 0 else x * 5 + 8 f = np.vectorize(f) # or use a different name … Read more
Is the ternary operator faster than an “if” condition in Java [duplicate]
Does it matter which I use? Yes! The second is vastly more readable. You are trading one line which concisely expresses what you want against nine lines of effectively clutter. Which is faster? Neither. Is it a better practice to use the shortest code whenever possible? Not “whenever possible” but certainly whenever possible without detriment … Read more
Why is this F# code so slow?
The problem is that the min3 function is compiled as a generic function that uses generic comparison (I thought this uses just IComparable, but it is actually more complicated – it would use structural comparison for F# types and it’s fairly complex logic). > let min3(a, b, c) = min a (min b c);; val … Read more
Favourite performance tuning tricks [closed]
Here is the handy-dandy list of things I always give to someone asking me about optimisation. We mainly use Sybase, but most of the advice will apply across the board. SQL Server, for example, comes with a host of performance monitoring / tuning bits, but if you don’t have anything like that (and maybe even … Read more
How is pattern matching in Scala implemented at the bytecode level?
The low level can be explored with a disassembler but the short answer is that it’s a bunch of if/elses where the predicate depends on the pattern case Sum(l,r) // instance of check followed by fetching the two arguments and assigning to two variables l and r but see below about custom extractors case “hello” … Read more
Xcode 4 – slow performance
If you purge the workspace file it helps speed it up. First, make sure Xcode isn’t open. Now find your project file. Right-click on it, and select Show Package Contents. Next, delete project.xcworkspace. Open Xcode and enjoy faster performance! Thanks to: http://meachware.blogspot.com/2011/06/speed-up-xcode-4.html Edit: I’ve gotten several comments about this noting that for some projects this … Read more