• A brief introduction of single chip microcomputer and its working principle


    First of all, what is a single chip microcomputer? Single chip microcomputer (SCM) is an integrated circuit chip, which uses VLSI technology to integrate CPU, memory and various IO interfaces with data processing technology. Composition and function Main components: central processing unit (CPU), memory, IO The main function of CPU is operation (various mathematical calculation) […]

  • Use of Uber JVM profiler


    background uber jvm profilerIt is used to collect JVM related indicators in distributed monitoring, such as CPU / memory / Io / GC information install Make sure to install Maven and JDK > = 8, directly MVN clean package java application explain It can be used directly by Java agent deployment use java -javaagent:jvm-profiler-1.0.0.jar=reporter=com.uber.profiling.reporters.KafkaOutputReporter,brokerList=’kafka1:9092′,topicPrefix=demo_,tag=tag-demo,metricInterval=5000,sampleInterval=0 -cp […]

  • Two retrying mechanisms of httpclient


    This paper is based onHttpClient 4.5.13 When using HTTP to request external services, it is often necessary to try again because of the instability of the network or the service itself. Of course, retrying can be implemented by hand code, but a better way is to implement it through the existing mechanism.HttpClientTwo types of retries […]

  • Division without division


    preface At the beginning of July, we challenged leetcode‘s question 29 (medium difficulty, which seems nothing to boast about). The problem requires that the function of integer division be realized without division, multiplication and modular operation. Since the divisor and divisor are integers, subtraction can be used to achieve division (what a naive idea). A […]

  • Android power consumption (1) — Android power analysis method and optimization


    1. Bottom current optimization The bottom current is debugged in the mobile phone flight mode. The bottom current data of each platform may be different. For details, please refer to the current consumption data document or release note from the release. In general, the upper limit of bottom current reference data is: The bottom current […]

  • Implementation of moving average filter in hand to hand teaching series


    [guide]: the previous article about IIR design, or some friends click to read. Although I don’t know how the viewers feel, but I think there is always a favor to read, so I decided to continue this series. This article talks about the average filter, this topic at first glance is very easy. However, some […]

  • Python sequence (3) list element access and counting


    1. Use the subscript to access the list elements directly. If the specified subscript does not exist, an exception will be thrown. >>> alist[3] 1 >>> alist[3]=5.5 >>> alist [1, 3, 5, 5.5, 3, 5, 1, 3, 5] >>> >>> alist[15] Traceback (most recent call last): File “”, line 1, in alist[15] IndexError: list index […]

  • Playing two tigers on the buzzer with Hongmeng OS


    This paper introduces how to use PWM interface of harmony OS IOT hardware subsystem to drive buzzer to play music on hispark Wi Fi IOT suite. API of square wave output with PWM The IOT hardware subsystem of Hongmeng system provides PWM related interface, and the interface header file is WiFi IOT_ PWM. H, in […]

  • Common i2i algorithm based on CF


    I2i (item to item) algorithm based on collaborative filtering is the most widely used recall algorithm in recommendation system. The base model, which is usually used as the start-up stage, is the benchmark of the subsequent algorithm iteration. It has the characteristics of convenient development and fast training speed, and the general effect is not […]

  • Linux kernel learning notes (6) — timer and time management


    timers and time management Time can be divided into relative and absolute time. When a process runs after 5 seconds, the current time of day (i.e. wall time) is absolute time. The absolute time is usually used when interacting with users. The system timer goes off (often called hitting or popping) at a preprogrammed frequency, […]

  • 09. Account locking when the number of password errors reaches the limit (spring, springmvc, JPA, Shiro)


    Requirement: lock the account when the number of wrong password entries reaches 3 times 1. Thinking analysis: 1.1. When can we know that the user‘s password is wrong?1.2. If the number of user password errors is recorded?1.3. How to realize account locking function?First of all, we can get the password error of the user. We […]

  • Android power optimization (7) — how to analyze the problem of wakeup source lock


    How to analyze wakelock (wakeup source) lock problem Locks are generally divided into: app holding locks through PowerManager and kernel wakelock The problem of upper locking is analyzed At present, the log of powermanagerservice will not be opened by default. You can modify the following: frameworks/base/services/core/java/com/android/server/power/PowerManagerService.java private static final boolean DEBUG = true; Through syslog: […]