Dear Zhan, Thanks very much for your kind reply! You may just refer to my another letter with title : [Beg for help] spark job with very low efficiency
I just need to apply spark to mathematica optimization by genetic algorithm , and theoretically the algorithm would iterate for lots of times.Then I lost into the problem:1) spark job will only have limited number of map successive calling before it meets one action ;2) action Function as collect / reduce will increase run time VERY MUCH ;3) if for parallelism, I understand rdd only with one partition will lose all the parallelism provided by spark , is it ... if it is with many partitions then it is difficult to randomly combine all its rows to generate another rdd. Thank you,Zhiliang On Tuesday, December 22, 2015 2:24 AM, Zhan Zhang <zzh...@hortonworks.com> wrote: In what situation, you have such cases? If there is no shuffle, you can collapse all these functions into one, right? In the meantime, it is not recommended to collectall data to driver. Thanks. Zhan Zhang On Dec 21, 2015, at 3:44 AM, Zhiliang Zhu <zchl.j...@yahoo.com.INVALID> wrote: Dear All, I need to iterator some job / rdd quite a lot of times, but just lost in the problem of spark only accept to call around 350 number of map before it meets one action Function , besides, dozens of action will obviously increase the run time.Is there any proper way ... As tested, there is piece of codes as follows: ...... 83 int count = 0; 84 JavaRDD<Integer> dataSet = jsc.parallelize(list, 1).cache(); //with only 1 partition 85 int m = 350; 86 JavaRDD<Integer> r = dataSet.cache(); 87 JavaRDD<Integer> t = null; 88 89 for(int j=0; j < m; ++j) { //outer loop to temporarily convert the rdd r to t 90 if(null != t) { 91 r = t; 92 } //inner loop to call map 350 times , if m is much more than 350 (for instance, around 400), then the job will throw exception message "15/12/21 19:36:17 ERROR yarn.ApplicationMaster: User class threw exception: java.lang.StackOverflowError java.lang.StackOverflowError") 93 for(int i=0; i < m; ++i) { 94 r = r.map(new Function<Integer, Integer>() { 95 @Override 96 public Integer call(Integer integer) { 97 double x = Math.random() * 2 - 1; 98 double y = Math.random() * 2 - 1; 99 return (x * x + y * y < 1) ? 1 : 0;100 }101 }); 104 }105106 List<Integer> lt = r.collect(); //then collect this rdd to get another rdd, however, dozens of action Function as collect is VERY MUCH COST107 t = jsc.parallelize(lt, 1).cache();108109 }110...... Thanks very much in advance!Zhiliang