如何在Spark中使用DenseVector作为键将groupByKey组为RDD？(How to groupByKey a RDD, with DenseVector as key, in Spark?)

 我想你可能会在这里混淆“异步”。 创建元组的过程将始终阻止。 因此，您可能想要做的是创建一个算法，该算法仅在需要时根据某些参数生成元组，然后将其缓存以供日后使用。 
 
 既然你已将其标记为node.js，我将假设这是感兴趣的编程语言。 基于这个假设，以及您实际上不希望阻塞的假设，您最好的选择是生成多个进程并管理创建这些元组的过程。 这是一个非常粗略的示例脚本（强调粗略 ）： 
 
var cluster = require('cluster');
var names = ['Jon', 'Stewart', 'Oliver'];

if (cluster.isWorker) {
  var count = +process.env.tupple_count;
  var tuples = [];

  // Process tuple here, then return it.

  process.send(JSON.stringify(tuples));
  return;
}

cluster.fork({ tupple_count: 2 }).on('message', function(msg) {
  // Receive tuple here:
  var tuple = JSON.parse(msg);
  console.log(tuple);
});

// Go about my life.
 
 然后你可以写一个通用算法来返回这些。 以下是关于如何执行此操作的良好链接： 从n返回k个元素的所有组合的算法 

I think you might be confusing "asynchronous" here. The process of creating the tuples will always block. So possibly what you'll want to do is create an algorithm that only generates a tuple when it's required, based on some parameters, then cache it for later.
 
Since you've tagged this as node.js I'm going to assume that's the programming language of interest. Based on that assumption, and the assumption that you actually don't want this to be blocking, your best bet is to spawn multiple processes and pipe out the process creating these tuples. Here's a very rough example script (emphasis on rough):
 
var cluster = require('cluster');
var names = ['Jon', 'Stewart', 'Oliver'];

if (cluster.isWorker) {
  var count = +process.env.tupple_count;
  var tuples = [];

  // Process tuple here, then return it.

  process.send(JSON.stringify(tuples));
  return;
}

cluster.fork({ tupple_count: 2 }).on('message', function(msg) {
  // Receive tuple here:
  var tuple = JSON.parse(msg);
  console.log(tuple);
});

// Go about my life.
 
Then you could write a general algorithm to return these. Here's a good link on how to do this: Algorithm to return all combinations of k elements from n