与Par集群

Question

我想使用matlab中的Par集群来并行地执行一些步骤。如果我在matlab交互模式下做下面的行，它将正确工作。但是，如果我将它放入一个函数中并执行它，那么它将产生下面的错误。

Par群集在函数中不工作吗？我犯了什么错？

代码：

function []=test()
  clust = parcluster();
  clust.NumWorkers = 4;

  job = createJob(clust);

  createTask(job,@(a,b)sum([a,b]),1,{1,2});
  %submit(job);
end

错误：

[Warning: Objects of class 'parallel.cluster.Local' cannot be saved to MAT    files.] 
[> In CustomGetSet>CustomGetSet.saveobj at 48
In distcomp.fileserializer.pPutFields>iSaveMat at 84
In distcomp.fileserializer.pPutFields at 62
In distcomp.fileserializer.createFields at 9
In CJSSupport>CJSSupport.initProperties at 224
In CJSSupport>CJSSupport.buildTasks at 531
In CJSJobMethods>CJSJobMethods.createTask at 113
In CJSIndependentJob>CJSIndependentJob.createTaskOnOneJob at 70
In Job.Job>Job.createTask at 269
In test at 7] 
[Warning: Objects of class 'parallel.job.CJSIndependentJob' cannot be saved to   MAT files.] 
[> In CustomGetSet>CustomGetSet.saveobj at 48
In distcomp.fileserializer.pPutFields>iSaveMat at 84
In distcomp.fileserializer.pPutFields at 62
In distcomp.fileserializer.createFields at 9
In CJSSupport>CJSSupport.initProperties at 224
In CJSSupport>CJSSupport.buildTasks at 531
In CJSJobMethods>CJSJobMethods.createTask at 113
In CJSIndependentJob>CJSIndependentJob.createTaskOnOneJob at 70
In Job.Job>Job.createTask at 269
In test at 7] 
[Warning: Objects of class 'parallel.cluster.Local' cannot be saved to MAT files.] 
[> In CustomGetSet>CustomGetSet.saveobj at 48
In distcomp.fileserializer.pPutFields>iSaveMat at 84
In distcomp.fileserializer.pPutFields at 62
In distcomp.fileserializer.createFields at 9
In CJSSupport>CJSSupport.initProperties at 224
In CJSSupport>CJSSupport.buildTasks at 531
In CJSJobMethods>CJSJobMethods.createTask at 113
In CJSIndependentJob>CJSIndependentJob.createTaskOnOneJob at 70
In Job.Job>Job.createTask at 269
In test at 7] 
[Warning: Objects of class 'parallel.job.CJSIndependentJob' cannot be saved to MAT files.] 
[> In CustomGetSet>CustomGetSet.saveobj at 48
In distcomp.fileserializer.pPutFields>iSaveMat at 84
In distcomp.fileserializer.pPutFields at 62
In distcomp.fileserializer.createFields at 9
In CJSSupport>CJSSupport.initProperties at 224
In CJSSupport>CJSSupport.buildTasks at 531
In CJSJobMethods>CJSJobMethods.createTask at 113
In CJSIndependentJob>CJSIndependentJob.createTaskOnOneJob at 70
In Job.Job>Job.createTask at 269
In test at 7] 

Answer 1

这里的问题实际上与parcluster和您使用它的方式无关。如果您在您的功能中提交了该职务，我怀疑它会像预期的那样工作，尽管发出了警告。

这些警告的原因相当模糊--正如警告所指出的那样，集群对象和作业对象无法以正常方式保存和加载。然而，你并没有(明确地)要求--那么为什么要警告呢？实际上，当您创建一个匿名函数时，工作空间中的所有变量都会附加到匿名函数中，以防它需要它们。(这是目前匿名函数的一个限制--它们捕获的上下文太多了)。然后，当函数存储在任务中时，将其保存到磁盘，并发出警告。

您可以通过两种方法中的一种避免此警告:如果您不感兴趣，可以禁用它，或者使用匿名函数以外的其他东西作为您的任务函数。

% Option 1: suppress warning
warning off 'parallel:cluster:CannotSaveCorrectly'

% Option 2: use an internal function
function []=test()
  clust = parcluster();
  clust.NumWorkers = 4;

  job = createJob(clust);

  createTask(job,@iSum,1,{1,2});
  submit(job);
end
function x = iSum(a, b)
  x = sum([a,b]);
end

编辑:从MATLAB R2015b开始，匿名函数工作区不再捕获太多的上下文，因此这个问题不应该再以同样的方式发生。