hash

Hash default value not being used [duplicate]

由 岁酱吖の 提交于 2019-12-24 00:01:09
问题 This question already has answers here : Strange, unexpected behavior (disappearing/changing values) when using Hash default value, e.g. Hash.new([]) (4 answers) Closed 4 years ago . Today I tried the following snippets of code and I don't understand why I get different results between them. As far as I can understand they are the same. One uses the default value off Hash and the other snippet creates an empty array for the key before it'll be accessed. Anyone who understands what's going on?

hash link reloads page

由 一个人想着一个人 提交于 2019-12-23 23:46:06
问题 I have a code snippet that is installed on third party websites. I can't get into the details, but it loads HTML, CSS and JS onto the page through the use of a <script> tag. Part of the code is a JS function that executes when this link is clicked: <a href="#">?</a> If there are JS errors on the page that prevent the function from executing, clicking the link obviously just adds the hash to the URL and takes the user to the top of the page. This is the expected fallback behavior. However, on

How can I override the []= method when subclassing a Ruby hash?

由 不打扰是莪最后的温柔 提交于 2019-12-23 22:42:10
问题 I have a class that extends Hash, and I want to track when a hash key is modified. What's the right syntax to override the [key]= syntactic method to accomplish this? I want to insert my code, then call the parent method. Is this possible with the C methods? I see from the docs that the underlying method is rb_hash_aset(VALUE hash, VALUE key, VALUE val) How does that get assigned to the bracket syntax? 回答1: The method signature is def []=(key, val) , and super to call the parent method. Here

How would a sdbm hash function be implemented in C#?

由 时光毁灭记忆、已成空白 提交于 2019-12-23 22:01:33
问题 How can a sdbm hash function (such as this) be implemented in C# ? 回答1: You can take the C code almost without changes: uint sdbm( string str ) { uint hash = 0; foreach( char ch in str ) { hash = ch + (hash << 6) + (hash << 16) - hash; } return hash; } Or did you think of something more sophisticated? 回答2: I don't have a C compiler set up so I can't test to see if it performs the same, but I think the following is correct: private static ulong SBDM(string str) { ulong hash = 0; foreach (char

Mysql优化思路

由 不打扰是莪最后的温柔 提交于 2019-12-23 21:41:29
一、总体优化思路 首先构建脚本观察查询数，连接数等数据，确定环境原因以及内部SQL执行原因，然后根据具体原因做具体处理。 二、构建脚本观察状态 mysqladmin -uroot -p ext \G 该命令可获取当前查询数量等信息，定时轮询并将结果重定向到文本中，然后处理成图表。 三、处理对策 1.若是规律性出现查询慢，考虑缓存雪崩问题。 对于该问题只需将缓存的失效时间处理成不要相近时间同时失效，失效时间尽量离散化，或者集中到午夜失效。 2.若非规律性查询缓慢，考虑设计缺乏优化 处理方法： a：开启profiling记录查询操作，并获取语句执行详细信息 show variables like '%profiling%'; set profiling=on; select count(*) from user; show profiles; show profile for query 1; >>> +--------------------------------+----------+ | Status | Duration | +--------------------------------+----------+ | starting | 0.000060 | | Executing hook on transaction | 0.000004 | | starting |

负载均衡算法

由 北城以北 提交于 2019-12-23 21:36:28
负载均衡算法可以分为下面几类： 任务平分类：可以按照平均分配或者加权平均分配的算法。 负载均衡类：按照服务器的负载，比如CPU负载，IO负载等进行分配（站在服务器的角度）。 性能最优类：客户端按照服务器的响应时间来分配请求（站在客户端的角度）。 Hash类：按照特定的信息进行hash值，然后分配给特定的服务器，比如按照IP hash算法，Session ID Hash算法，或者按照用户的ID hash等等。 一、任务平分类 轮询算法 该算法实现简单，即轮询每个服务器，分别将强求发送到不同的服务器中，不过对于某些场景，比如购物车业务会造成分布式session一致性问题。 而且该算法对于服务器的新旧，好坏程度无感知，如64核和32核的服务器的负载应当不同。 加权轮询 该算法解决上面的问题，可以按照服务器的核数等情况分配不同数量的请求 ，比如64核的服务器请求数应当多于32核的服务器。 但是该算也不能避免分布式session一致性的问题，也无法感知服务器的运行状态。（运行状态即服务器正在运行时的CPU负载以及IO负载）。 二、负载均衡类 负载最低优先算法 该算法解决了轮询无法感知服务器的运行状态的问题。 对于LVS负载均衡设备，可以通过“连接数”来衡量服务器的负载，连接数越多，负载越高。 对于Nginx负载均衡设备，可以通过“HTTP请求数”来衡量服务器负载等。 缺点：

How do I replace all the values in a hash with a new value?

由 最后都变了- 提交于 2019-12-23 20:37:10
问题 Let's say I have an arbitrarily deep nested Hash h : h = { :foo => { :bar => 1 }, :baz => 10, :quux => { :swozz => {:muux => 1000}, :grimel => 200 } # ... } And let's say I have a class C defined as: class C attr_accessor :dict end How do I replace all nested values in h so that they are now C instances with the dict attribute set to that value? For instance, in the above example, I'd expect to have something like: h = { :foo => <C @dict={:bar => 1}>, :baz => 10, :quux => <C @dict={:swozz =>

Order preserving minimal perfect hash functions

由 感情迁移 提交于 2019-12-23 20:33:03
问题 I want to implement an OPMPH function for the words in a dictionary in C++. How do I do it? Thanks! 回答1: Have you looked at these papers? http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.84.4018&rep=rep1&type=pdf http://dx.doi.org/10.1016/0020-0190(92)90220-P (the short form link that leads to a very long link at http://www.sciencedirect.com/) http://eprints.cs.vt.edu/archive/00000248/01/TR-91-01.pdf 回答2: Limit your word length to 6 letters or less and you might be able to make it

Playing with Hashes from a FTP flow in Perl

由 时光怂恿深爱的人放手 提交于 2019-12-23 20:15:15
问题 Ok, so I'm obviously having some issues understanding how to work with hashes. Long story short, I'm attempting to parse through an ftp log and find the relevant flows for a specific search criteria. Basically what I'm trying to make it do is, say I have an IP address or a user name, it first does a pretty simple grep to try to minimize any data I don't need and send the output to an external file. If I'm searching for username testing1, then it does a grep on testing1 and sends the output to

Using hash to check if page with $_POST values was refreshed

由 a 夏天 提交于 2019-12-23 19:53:16
问题 When posting a form to the same PHP page, what is the correct method to find if the page was accidentally refreshed instead of submitted again? Here's what I'm using right now: $tmp = implode('',$_POST); $myHash = md5($tmp); if(isset($_SESSION["myHash"]) && $_SESSION["myHash"] == $myHash) { header("Location: index.php"); // page refreshed, send user somewhere else die(); } else { $_SESSION["myHash"] = $myHash; } // continue processing... Is there anything wrong with this solution? UPDATE: An
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