• How to measure Linux performance and avoid the most typical error: disk


    In this series, we will discuss Linux performance measurement and how to measure it correctly. Linux performance is a very broad topic, so we will focus on the four main resources that usually improve system performance — CPU, memory, disk storage and network.As far as disks are concerned, there are actually two things you need […]

  • The lecture of Statistical Science


    01. Preface We talked about multiple linear regression. In this article, let’s talk about gradual regression. What is stepwise regression? It’s literally a step-by-step return. We know that the element in multiple regression refers to the independent variable, and multiple variables are multiple independent variables, namely multiple X. One of the questions we need to […]

  • A case of using union index


    In practice, full table scanning is always avoided, so slow table scanning is avoidedsqlIndex on some fields in. The significance of index building is that the original operation of scanning and operation in the table is executed in the index to reduce the number of scanning rows in the table, so the query speed is […]

  • Hypothesis testing in statistics series


    Last time I wrote the confidence level and confidence interval in statistics, the article has a good response. This time I’ll try to write the hypothesis test in statistics. The core of hypothesis testing is actually the method of disprovement. Proof to the contrary is a concept in mathematics, that is, if you want to […]

  • Hypothesis test: use the p value to accept or reject your hypothesis


    AuthorCompile | VKSource | analytics vidhya introduce Test is one of the most basic concepts in statistics. Not only in data science, hypothesis testing is very important in various fields. Want to know how to do it? Let’s take an example. Now there’s a lifebuoy shower gel. Shower Gel manufacturers claim it kills 99.9% of […]

  • How to do a perfect abtest?


    This article starts with WeChat official account of vivo Internet technology.Link: https://mp.weixin.qq.com/s/mO5MdwG7apD6RzDhFwZhogAuthor: duzhimin More and more companies are trying abtest, either building their own systems or relying on third-party systems. So what are the necessary basic knowledge when we conduct abtest? How to carry out AB experiment step by step? In this paper, we will […]

  • Regular


    PHP common checks #Android or not function is_android() { return stripos($_SERVER[‘HTTP_USER_AGENT’], “Android”); } #IPhone function is_iphone() { return stripos($_SERVER[‘HTTP_USER_AGENT’], “iPhone”); } //Determine whether Ajax request function isAjax() { return (isset($_SERVER[‘HTTP_X_REQUESTED_WITH’]) && ($_SERVER[‘HTTP_X_REQUESTED_WITH’] == ‘XMLHttpRequest’)); } Regular rules in PHP #ID card verification $preg = ‘/^(\d{15}$|^\d{18}$|^\d{17}(\d|X|x))$/’; if (!preg_match($preg, $idNumber)) { return false; } #Mobile phone number […]

  • Preliminary exploration of ES6


    I’ve been watching react for two days. Exposure to ES6. Talk about some superficial views. ES6 is actually an abbreviation. Its scientific name is ECMAScript 2015, or ES 2015. Is a new version of the JavaScript language. Of course, the new version has new features. ES6 basically irons out the unique things in JavaScript. I […]

  • Kafka-0-outline


    Kafka- introduction Definition Basic concepts Characteristic Application scenario Kafka cluster deployment Preparation Zookeeper single machine cluster Kafka single machine cluster Common configuration description Kafka partial principle topic & partition & segment Definition Physical storage structure of partition Significance of zoning The significance of segmentation The meaning of timeindex message format Leader & cluster discovery mechanism […]

  • Cleancode [1]: meaningful naming


    Why meaningful naming: We’ve all said that one day we’ll go back and clean up the bad code, but in the end we’ll leave it behind. Later is equal to never, we need to act immediately, write elegant code. In the process of writing code, reading accounts for a large proportion, so first of all, […]

  • What is the meaning of introducing internal classes in Java?


    Preface This is a good question, because it reminds me of the “impulse to use” when I first learned internal classes. As a result, my code is full of layers of nested inner classes. Not only do static domain errors often occur (internal classes are not allowed to have static member fields), but for some […]