That depends entirely on the ISA you’re compiling for, and the quality of your compiler’s optimizer. Don’t optimize prematurely: profile first to find your bottlenecks. That said, in x86, you’ll find that both are equally fast in most cases. In both cases, you’ll have a comparison (cmp) and a conditional jump (jCC) instructions. However, for … Read more
I worked up a similar example that fails the same way: using System; using System.Runtime.CompilerServices; public class Program { static void Main() { Console.Write(Verify(Test.Create())); Console.ReadLine(); } //[MethodImpl(MethodImplOptions.NoInlining)] static bool Verify(IDisposable item) { return item is Test; } struct Test : IDisposable { public void Dispose() { } public static Test Create() { return new Test(); … Read more
Seems to be all 64-bit processors has SSE2. Since compiler option always switched on by default no need to switch it on manually. From Wikipedia: SSE instructions: The original AMD64 architecture adopted Intel’s SSE and SSE2 as core instructions. SSE3 instructions were added in April 2005. SSE2 replaces the x87 instruction set’s IEEE 80-bit precision … Read more
You can usually bring all the data in two or three big queries instead of on twenty small ones. Minimizing the amount of queries is as important as, if not most important than, writing optimal queries to maximize performace. Of course you should always analyze the query plans and aim towards optimal queries, be them … Read more
This constraint t[0] + t[1] = 1 would be an equality (type=”eq”) constraint, where you make a function that must equal zero: def con(t): return t[0] + t[1] – 1 Then you make a dict of your constraint (list of dicts if more than one): cons = {‘type’:’eq’, ‘fun’: con} I’ve never tried it, but … Read more
In this situation changing while() to for() is not an optimization. There is simply no way to know from bytecode which one was used in a source code. There are many situations when: while(x) is the same as: for(;x;) Suppose we have a three similar java applications – one with while() statement, and two with … Read more
Optimization in Java is mostly done by the JIT compiler at runtime. Hence there is no point trying to instruct it to optimize a certain way at compile time (when it is creating only bytecode anyway). The JIT will almost surely make better decisions on the spot, knowing the exact environment and observing the actual … Read more
Courtesy of William Chan and Google. 30-70% faster than memcpy in Microsoft Visual Studio 2005. void X_aligned_memcpy_sse2(void* dest, const void* src, const unsigned long size) { __asm { mov esi, src; //src pointer mov edi, dest; //dest pointer mov ebx, size; //ebx is our counter shr ebx, 7; //divide by 128 (8 * 128bit registers) … Read more
There is a huge difference. The __len__() method is a hook method. The len() function will use the __len__ method if present to query your object for it’s length. The normal API people expect to use is the len() method, using a .len attribute instead would deviate from that norm. If the length of self.data … Read more
The whole point of a websocket connection is that you don’t ever have to ping the app for changes. Instead, the client just connects once and then the server can just directly send the client changes whenever they are available. The client never has to ask. The server just sends data when it’s available. For … Read more