optimization

问题 I have a very large structure, which I want to ensure is not copied needlessly. How can I make a copy-on-write container for it? 回答1: A copy-on-write is usually a struct wrapper over some backing object. public final class MutableHeapStore<T>: NonObjectiveCBase { public typealias Storage = T public private(set) var storage: Storage public init(storage: Storage) { self.storage = storage } } public struct COW<T> { public typealias Storage = MutableHeapStore<T> public typealias Value = T public

问题 Am using three.js How can I control the rendering order? Let's say I have three plane geometries, and want to render them in a specific order regardless of their spatial position. thanks 回答1: You can set renderer.sortObjects = false; and the objects will be rendered in the order they were added to the scene. Alternatively, you can leave sortObjects as true , the default, and specify for each object a value for object.renderOrder . For more detail, see Transparent objects in Threejs Another

问题 So my question is about variable accessing speed in Java. Today in my "CS" (if you can call it that) the teacher presented a similar example to the following of a List: public class ListExample<T> { private Node<T> head; private Node<T> tail; private class Node<T> { /* ... */ } public void append(T content) { if (!isEmpty()) { Node<T> dummy = new Node<T>(content); head = dummy; tail = dummy; head.setNext(head); // or this dummy.setNext(dummy); } else { /* ... */ } } // more methods // ... }

问题 So my question is about variable accessing speed in Java. Today in my "CS" (if you can call it that) the teacher presented a similar example to the following of a List: public class ListExample<T> { private Node<T> head; private Node<T> tail; private class Node<T> { /* ... */ } public void append(T content) { if (!isEmpty()) { Node<T> dummy = new Node<T>(content); head = dummy; tail = dummy; head.setNext(head); // or this dummy.setNext(dummy); } else { /* ... */ } } // more methods // ... }

问题 It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center. Closed 6 years ago . I have a piece of MySQL code that searches through a quite lengthy mysql database. When done multiple times, it takes a long time, although the only thing I need from the code is to check the existence of at

问题 This question already has answers here : How can I sort two vectors in the same way, with criteria that uses only one of the vectors? (8 answers) Closed 3 years ago . I have 2 vectors which store properties that are "linked". This is what I mean: std::vector<std::string> names; std::vector<int> ids; // Name of object with an ID of 5 auto name = names[std::find(ids.begin(), ids.end(), 5) - ids.begin()]; Each object has a name and an ID, and so the object at index n has a name of name[n] and an

问题 I'm trying to figure out what is the most efficient way to parse data from a file using Lua. For example lets say I have a file (example.txt) with something like this in it: 0, Data 74, Instance 4294967295, User 255, Time If I only want the numbers before the "," I could think of a few ways to get the information. I'd start out by getting the data with f = io.open(example.txt) and then use a for loop to parse each line of f . This leads to the heart of my question. What is the most efficient

问题 Although I'm using Rails, this question is more about database design. I have several entities in my database, with the schema a bit like this: http://fishwebby.posterous.com/40423840 If I want to get a list of people and order it by surname, that's no problem. However, if I want to get a list of people, ordered by surname, enrolled in a particular group, I have to use an SQL statement that includes several joins across four tables, something like this: SELECT group_enrolment.*, person.* FROM

问题 I have a React / Redux app that renders a grid of PureComponents. I want the components to only re-render when a prop value has changed, but in fact all components re-render on any update to store. The issue appears to be caused by an array property. I've reproduced the issue in this sandbox. In this minimal example, two instances of the Cell component are rendered. Each displays a value that is separately recorded in the store, and can be incremented or decremented separately with a button.

问题 I'm making a 3D game, where the player's back should always be facing the camera and he should move in that direction. I didn't come to the "back facing the camera" part yet, but I believe that it will be simple once I figure out how to move the player in the right direction... Though it is a 3D coordinate system, height can be ignored (z-axis) because no matter how high the camera is, the player should always be going in the same speed (the camera system is planned to function much like in