fifo

简单的java缓存实现

由 五迷三道 提交于 2021-02-17 17:07:11
提到缓存，不得不提就是缓存算法(淘汰算法)，常见算法有LRU、LFU和FIFO等算法，每种算法各有各的优势和缺点及适应环境。 1、LRU(Least Recently Used ，最近最少使用) 算法根据数据的最近访问记录来淘汰数据，其原理是如果数据最近被访问过，将来被访问的几概率相对比较高，最常见的实现是使用一个链表保存缓存数据，详细具体算法如下： 1. 新数据插入到链表头部； 2. 每当缓存数据命中，则将数据移到链表头部； 3. 当链表满的时候，将链表尾部的数据丢弃； 2、LFU(Least Frequently Used，最不经常使用) 算法根据数据的历史访问频率来淘汰数据，其原理是如果数据过去被访问次数越多，将来被访问的几概率相对比较高。LFU的每个数据块都有一个引用计数，所有数据块按照引用计数排序，具有相同引用计数的数据块则按照时间排序。 具体算法如下： 1. 新加入数据插入到队列尾部（因为引用计数为1）； 2. 队列中的数据被访问后，引用计数增加，队列重新排序； 3. 当需要淘汰数据时，将已经排序的列表最后的数据块删除； 3、FIFO(First In First Out ，先进先出) 算法是根据先进先出原理来淘汰数据的，实现上是最简单的一种,具体算法如下： 1. 新访问的数据插入FIFO队列尾部，数据在FIFO队列中顺序移动； 2. 淘汰FIFO队列头部的数据；

Teradata FIFO Script

由 大憨熊 提交于 2021-02-07 10:45:40
问题 There is an old stack post (First-in-first-out (FIFO) inventory costing) that contains the Set-based Speed Phreakery: The FIFO Stock Inventory SQL Problem: (https://www.simple-talk.com/sql/performance/set-based-speed-phreakery-the-fifo-stock-inventory-sql-problem/). I have been trying to adapt it from SQL Server to Teradata SQL but have discovered that: (a) Teradata can only handle one CTE with statement (b) You cannot use cross apply (c) You cannot use hint indexes? My questions are: Is

FIFO with one READER and multiple WRITER in BASH/SH

由 僤鯓⒐⒋嵵緔 提交于 2021-01-29 07:42:55
问题 I have one named pipe (FIFO) say : 'MY_FIFO' One process reads the fifo from multiple processes to get instructions. (1) reader bash script: while read LINE < 'MY_FIFO' do # process line done (many) writer bash script: while [ 1 ] do INSTRUCTION = # get an instruction echo $INSTRUCTION > 'MY_FIFO' done This works fine to pass instructions to the reader when we have 1 writer or that the writers don't write at the same time. But if we have many writers writing at the same time, the reader gets

How can I monitor a FIFO?

由 為{幸葍}努か 提交于 2021-01-28 09:28:25
问题 I want to debug an issue between two processes ideally by setting up a read-only terminal window of that traffic. Is this something I can simply use existing, standard linux utilities for? The FIFO lives at /run/myfifo and is created in one of the processes with: /* Create a FIFO if one doesn't already exist */ int createFifo(char *filepath) { if (access(path, F_OK) == -1) { return mkfifo(filepath, S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH); } return 0; } tail -F /run/myfifo ?

How can I monitor a FIFO?

由 匆匆过客 提交于 2021-01-28 09:24:23
问题 I want to debug an issue between two processes ideally by setting up a read-only terminal window of that traffic. Is this something I can simply use existing, standard linux utilities for? The FIFO lives at /run/myfifo and is created in one of the processes with: /* Create a FIFO if one doesn't already exist */ int createFifo(char *filepath) { if (access(path, F_OK) == -1) { return mkfifo(filepath, S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH); } return 0; } tail -F /run/myfifo ?

Create a column to calculate the portion of balance for every shipment according to FIFO

由 此生再无相见时 提交于 2021-01-05 12:36:14
问题 I have a query to get Stock-items with it's Balance and Its receiving Transactions cods with its quantity Ordered By date, And i Want to create a column which has only the proportion Balance of every RS Code according to First in First Out Principle. As An Example in the attached sample we have StockItemId = (2222,2262,2263). and the expected result will be AS: As in Pic the Balance of every row in RS_Portion is depending on the Quantity of the Code and the sum of RS_Portion of every item

LRU vs FIFO vs Random

由 假装没事ソ 提交于 2020-12-31 05:47:37
问题 When there is a page fault or a cache miss we can use either the Least Recently Used (LRU), First in Fist Out (FIFO) or Random replacement algorithms. I was wondering, which one provides the best performance aka the least possible future cache miss'/page faults? Architecture: Coldfire processor 回答1: No perfect caching policy exists because it would require knowledge of the future (how a program will access memory). But, some are measurably better than others in the common memory access

LRU vs FIFO vs Random

由 早过忘川 提交于 2020-12-31 05:41:47
问题 When there is a page fault or a cache miss we can use either the Least Recently Used (LRU), First in Fist Out (FIFO) or Random replacement algorithms. I was wondering, which one provides the best performance aka the least possible future cache miss'/page faults? Architecture: Coldfire processor 回答1: No perfect caching policy exists because it would require knowledge of the future (how a program will access memory). But, some are measurably better than others in the common memory access

LRU vs FIFO vs Random

由 梦想与她 提交于 2020-12-31 05:41:01
问题 When there is a page fault or a cache miss we can use either the Least Recently Used (LRU), First in Fist Out (FIFO) or Random replacement algorithms. I was wondering, which one provides the best performance aka the least possible future cache miss'/page faults? Architecture: Coldfire processor 回答1: No perfect caching policy exists because it would require knowledge of the future (how a program will access memory). But, some are measurably better than others in the common memory access

ARM11 S3C6410系列教程之二：串口

由 為{幸葍}努か 提交于 2020-12-26 04:26:16
对于一个微处理器，最常用也是最简单的接口就是串口，它不需要太多的管脚，也不需要太多的硬件电路，如果不放心，增加一个max232可以达到万无一失的境地，完成数据的传输。 本文引用地址： http://www.eepw.com.cn/article/203123.htm 　　S3C6410拥有187个复用功能的I/O端口，这些端口可以分为17组，具体如下： 　　S3C6410X UART 支持的比特率可达到 3Mbps。每个 UART 包含两个 64-byte FIFO ’s用于发送和接收数据。我们可以这样理解，当配置好 寄存器 后，我们可以从相应的缓存区读取或者发送相应的数据。通过上面的描述可以看出，S3C6410的GPA和GPB为串口。现在我以串口0为例介绍S3C6410的串口如何配置。对与串口0，通过设置GPACON为相应的数据完成串口设置。 　　串口0的硬件连接图如下： 　　串口0的配置 寄存器 意义如下： 　　通过配置GPACON 寄存器 ，将端口使能串口模式， 　　GPACON &= ~0xff;/*清除寄存器并设置为串口模式*/ 　　GPACON |= 0x22; 　　对于串口的功能设置，通过ULCON0来进行设置，该寄存器意义如下： 对于发送和接受的模式设置通过配置UCON0进行设置，该 寄存器 意义如下： 本文引用地址： http://www.eepw.com.cn
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