shuffle | 易学教程

join shuffle

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什么是宽窄依赖，及特殊join算子，join时何时产生shuffle，何时不产生shuffle 转载从0到1哦发布于2018-11-11 15:39:18 阅读数 696 收藏展开 1、什么是宽窄依赖，宽依赖：发生shuffle时，一定会产生宽依赖，宽依赖是一个RDD中的一个Partition被多个子Partition所依赖（一个父亲多有儿子），也就是说每一个父RDD的Partition中的数据，都可能传输一部分到下一个RDD的多个partition中，此时一定会发生shuffle 窄依赖：一个RDD中的一个 Partition最多被一个子 Partition所依赖（一个父亲有一个儿子） 2、 Spark中产生宽窄依赖的依据是shuffle，当发生shuffle时，会产生宽依赖，基本上shuffle算子都会产生宽依赖，但是join除外，在执行join算子之前如果先执行groupByKey，执行groupByKey之后，会把相同的key分到同一个分区，再执行join算子，join算子是把key相同的进行join（只是对于k v形式的数据可以使用），不一定会产生shuffle ，有可能发生shuffle，也有可能不发生最后返回的结果是（Key,(rdd1的v,rdd2的v)）,如下平行化创建，两个RDD，对其进行Join。这中情况下就不一定会产生shuffle

Collections.shuffle()

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Collections.shuffle() 洗牌方法应用于简易发扑克牌程序顾名思义，shuffle是洗牌的意思，所以这个方法的作用是将list中的循序打乱，参数放入List 函数源代码一个简单的例子： @Test private void test1 ( ) { ArrayList < String > num = new ArrayList < String > ( ) ; num . add ( "A" ) ; num . add ( "2" ) ; num . add ( "3" ) ; num . add ( "4" ) ; num . add ( "5" ) ; num . add ( "6" ) ; num . add ( "7" ) ; num . add ( "8" ) ; num . add ( "9" ) ; num . add ( "10" ) ; num . add ( "J" ) ; num . add ( "Q" ) ; num . add ( "K" ) ; System.out.println<span class=

Shuffling an Array in Android

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问题 I am very new to Programming and am trying to make a program that takes a number from an EditText then generates and Array which is then shuffled and the shuffled numbers come out on toast. This is what my code looks like. I have tried reading through a number of other posts on shuffling arrays but I haven't been able to get this to work. public class Home extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R

Workaround for suhosin.mt_srand.ignore to consistently shuffle an array in PHP?

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问题 I have a PHP script which needs to randomise an array with consistent results, so it can present the first few items to the user and they can then pull in more results from the same shuffled set if they want to. What I'm currently using is this (based on the Fisher Yates algorithm I believe): function shuffle(&$array, $seed) { mt_srand($seed); for ($a=count($array)-1; $a>0; $a--) { $b = mt_rand(0, $a); $temp = $array[$a]; $array[$a] = $array[$b]; $array[$b] = $temp; } } Which works fine on my

Shuffle instruction in CUDA not working

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问题 I have got problem with shuffle instruction in CUDA 5.0. This is snippet of my kernel. It is inside the loop. Print is there only for debug purpose because I can't use ordinary debugger: ... tex_val = tex2D(srcTexRef, threadIdx.x + w, y_pos); if (threadIdx.x == 0) { left = left_value[y_pos]; } else { printf("thread %d; shfl value: %f \n", threadIdx.x, __shfl_up(value, 1)); left = __shfl_up(value, 1); } printf("thread %d; value: %f; tex_val: %f; left: %f \n", threadIdx.x, value, tex_val, left)

Use and utility of std::shuffle?

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问题 If you look to the specifications of random shuffle in C++11, there are 3 functions. My question is what is the typical use and advantage of : template< class RandomIt, class URNG > void shuffle( RandomIt first, RandomIt last, URNG&& g ); compared to: template< class RandomIt > void random_shuffle( RandomIt first, RandomIt last ); I mean, it seems that whatever URNG is (a uniform distribution), the result will be the same (from a statistical point of view). The only point I see, is that std:

php shuffle a pack of cards

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问题 I would like to use php to create a collection of random bridge hands. I thought that I could encode an ordered pack of cards as the string $deal below (I like it that there are 52 letters when considering both upper and lower case). I discovered the php function str_shuffle . So I thought that I could do the following: $pack = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'; $shuffledPack = str_shuffle($pack); This gives me the desired output. My question is: does str_shuffle give

random.shuffle Randomness

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问题 I am trying to write a genetic algorithm for homework to solve the travelling salesman problem. One of the mutation functions that I'm trying is to use random.shuffle on the tour. When I read the documentation for random.shuffle , I see: shuffle(self, x, random=None, int=<type 'int'>) method of random.Random instance x, random=random.random -> shuffle list x in place; return None. Optional arg random is a 0-argument function returning a random float in [0.0, 1.0); by default, the standard

How do I randomly jumble sections of a URL seperated by “/”?

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问题 I’m wondering how to jumble sections of this URL as / as the separator: http://fujifilm.in/en/products/consumer_products/digital_cameras/x/fujifilm_x_t1/ I’m looking for all combinations of results, like http://fujifilm.in/en/products/consumer_products/digital_cameras/x/fujifilm_x_t1/ http://fujifilm.in/en/products/consumer_products/digital_cameras/x http://fujifilm.in/en/products/consumer_products/digital_cameras http://fujifilm.in/en/products/consumer_products http://fujifilm.in/en/products

Jquery if else colour shuffle (passing a variable)

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问题 This is regarding this question i asked on this link:PHP CSS Colour Shuffle array? I have changed and added more code and have a different question hence why i've opened a new thread. I am using php and jQuery to shuffle colours every time the page is refreshed. At the moment this works fine. But i have a jQuery function where i grab some elements and on a hoverstate show the shuffle colour. Now this does work but it's showing css standard default red,blue,green ect and not even displaying