QA Official

Basic Concept of Cross Entropy

https://qaofficial.com/post/2019/05/21/68872-basic-concept-of-cross-entropy.html 2019-05-21
language model performance is usually measured by cross entropy and perplexity.The meaning of cross entropy is the difficulty of text recognition with this model, or from the point of view of compression, each word needs to be encoded with several bits on average.The meaning of complexity is to use the model to represent the average number of branches of this text, and its reciprocal can be regarded as the average probability of each word.

Is it possible to steal fingerprints stored in Android phones?

https://qaofficial.com/post/2019/05/21/68884-is-it-possible-to-steal-fingerprints-stored-in-android-phones.html 2019-05-21
ARM inside has Normal World and Secure World, app can only access Normal World data, Normal World cannot access Secure World, and can only call the interface provided by Secure World to process data. This hardware for fingerprint acquisition is in Secure World. After fingerprint acquisition, it is encrypted and signed in Secure World, and then the result is transferred to Normal World to be saved, so the processed fingerprint data is saved.

Java Implementation of Selective Sorting Algorithm

https://qaofficial.com/post/2019/05/21/69763-java-implementation-of-selective-sorting-algorithm.html 2019-05-21
The basic idea of selecting and sorting is to first find the smallest element in the array, and then exchange the position of that element with the first element in the array. Find the smallest element among the remaining elements, and then exchange the position of that element with the second element in the array. This loop finally realizes the sorting of arrays code is as follows: public class Selection

Kodi (software)-Set up Video Cache (Solve the Catton Problem of LAN Video Playback)

https://qaofficial.com/post/2019/05/21/71043-kodi-software-set-up-video-cache-solve-the-catton-problem-of-lan-video-playback.html 2019-05-21
Kodi (software)-Set up Video Cache (Solve the Catton Problem of LAN Video Playback) The original text comes from: www.hangge.comreprint please keep the original link: http://www.hangge.com/blog/cache/detail_1705.html

MD5 digital signature encryption of character strings

https://qaofficial.com/post/2019/05/21/68881-md5-digital-signature-encryption-of-character-strings.html 2019-05-21
The specified string is encrypted by MD5, which is used to "compress" large-capacity information into a confidential format (that is, to convert a byte string of any length into a hexadecimal digit string of a certain length) before signing the private key with digital signature software.In addition to MD5, sha-1, RIPEMD and Haval are more famous among them. import java.io.UnsupportedEncodingException; import java.security.MessageDigest; import java.security.NoSuchAlgorithmException; public class MD5Tool { /** *

Mediator

https://qaofficial.com/post/2019/05/21/70999-mediator.html 2019-05-21
mediation mode Mediator, a kind of design mode that has been bothering me for many years, is that the mediation mode may be used to solve problems between classes that you have been using all the time. today, I also encountered such problems without specifying them. after pondering for a long time, I still want to find out why. Discuss whether this mode is What? or not

Message Digest, Digital Fingerprint, Digital Signature, digital time-stamp Technology

https://qaofficial.com/post/2019/05/21/68900-message-digest-digital-fingerprint-digital-signature-digital-time-stamp-technology.html 2019-05-21
Message Digest Algorithm and Digital Fingerprint hash algorithmHASH algorithm inputs a string of variable length and returns a string of fixed length, called HASH value. One-way HASH algorithm is used to generate information summary.MD2, MD4 and MD5(MD stands for information digest) are widely used HASH functions. HASH algorithm mainly solves two problems: in a specific time, it is impossible to find the original message that generates a specific HASH value after HASH operation, nor can it find two different messages that generate the same HASH value after HASH operation.

One of Machine Learning Algorithms: 5 Minutes Hands-on KNN

https://qaofficial.com/post/2019/05/21/68910-one-of-machine-learning-algorithms-5-minutes-hands-on-knn.html 2019-05-21
1. Case: This data uses the number of fights and kisses to define the movie type. Kisses are mostly Romance type, while fights are mostly action movies. 2. Question: Now there is a movie with an unknown name, with 18 fights and 90 kisses. What kind of movie does it belong to? 3.Sampe code: import numpy as np from sklearn import neighbors from sklearn.externals import joblib

RF Training Model Process in Mobile Recommendation Algorithm

https://qaofficial.com/post/2019/05/21/70886-rf-training-model-process-in-mobile-recommendation-algorithm.html 2019-05-21
First is the function: function: generation and splitting to training set & validset def valid_train_set_construct(valid_ratio = 0.5, valid_sub_ratio = 0.5, train_np_ratio = 1, train_sub_ratio = 0.5): # generation of train set @param valid_ratio: float ~ [0~1], the valid set ratio in total set and the rest is train set @param valid_sub_ratio: float ~ (0~1), random sample ratio of valid set @param train_np_ratio: (1~1200), the sub-sample ratio of training set for

Selected Sorting Examples and Analysis

https://qaofficial.com/post/2019/05/21/69757-selected-sorting-examples-and-analysis.html 2019-05-21
This article introduces an example of Selection Sort and a brief analysis. The sample code is as follows: #include <stdio.h> #include <stdlib.h> int main() { /* 选择排序法函数声明 */ int sort(int array[], int n); int num[5] = {0}; int i = 0; /* 接收用户输入的5个整型数 */ printf("please input 5 integer numbers: \n"); for