From MS Partition I, section 12.1 (Supported data types): The signed integer types (int8, int16, int32, int64, and native int) and their corresponding unsigned integer types (unsigned int8, unsigned int16, unsigned int32, unsigned int64, and native unsigned int) differ only in how the bits of the integer are interpreted. For those operations in which an … Read more
using 1 char array could work a bit better int length = s.length(); char[] oldChars = new char[length]; s.getChars(0, length, oldChars, 0); int newLen = 0; for (int j = 0; j < length; j++) { char ch = oldChars[j]; if (ch >= ‘ ‘) { oldChars[newLen] = ch; newLen++; } } s = new … Read more
If you “fix” the alignment, all give the same assembly language output (with GCC): struct alignas(std::int64_t) Point { std::int32_t x, y; }; Demo As a note, some correct/legal ways to do some stuff (as type punning) is to use memcpy, so having specific optimization (or be more aggressive) when using that function seems logical.
Yes, many CPUs can perform multiplication in 1 or 2 clock cycles but division always takes longer (although FP division is sometimes faster than integer division). If you look at this answer you will see that division can exceed 24 cycles. Why does division take so much longer than multiplication? If you remember back to … Read more
Loop unrolling makes sense if you can break dependency chains. This gives a out of order or super-scalar CPU the possibility to schedule things better and thus run faster. A simple example: for (int i=0; i<n; i++) { sum += data[i]; } Here the dependency chain of the arguments is very short. If you get … Read more
The tree is massive By far the most expensive thing a processor ever does is not executing instructions, it is accessing memory. The execution core of a modern CPU is many times faster than the memory bus. A problem related to distance, the further an electrical signal has to travel, the harder it gets to … Read more
The answers so far are spot-on. Using isset in this case is faster because It uses an O(1) hash search on the key whereas in_array must check every value until it finds a match. Being an opcode, it has less overhead than calling the in_array built-in function. These can be demonstrated by using an array … 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
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