20140427 parallel programming_zlobin_lecture11

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20140427 parallel programming_zlobin_lecture11

  1. 1. Map/Reduce Обзор решений Алексей Злобин alexey.zlobin@gmail.com
  2. 2. Sample job: driver public static void main(String[] a) throws Exception { Configuration conf = new Configuration(); job.setOutputKeyClass(Text.class); job.setOutputValueClass(IntWritable.class); job.setReducerClass(Reduce.class); job.setInputFormatClass(TextInputFormat.class); job.setOutputFormatClass(TextOutputFormat.class); FileInputFormat.addInputPath(job, new Path(a[0])); FileOutputFormat.setOutputPath(job, new Path(a[1])); job.waitForCompletion(true); }
  3. 3. Sample job: mapper class M extends Mapper<LongWritable, Text, Text, IntWritable> { private final static IntWritable one = new IntWritable(1); private Text word = new Text(); public void map(LongWritable k, Text v, Context ctx) { String line = v.toString(); StringTokenizer tokenizer = new StringTokenizer(line); while (tokenizer.hasMoreTokens()) { word.set(tokenizer.nextToken()); ctx.write(word, one); } } }
  4. 4. Sample job: reducer class R extends Reducer<Text, IntWritable, Text, IntWritable> { public void reduce(Text k, Iterable<IntWritable> v, Context ctx) { int sum = 0; for (IntWritable val : v) sum += val.get(); context.write(k, new IntWritable(sum)); } }
  5. 5. Pig snippet raw = LOAD 'excite.log' USING PigStorage('t') AS (user, time, qry); clean1 = FILTER raw BY org.apache.pig.tutorial.NonURLDetector(qry); clean2 = FOREACH clean1 GENERATE user, time, org.apache.pig.tutorial.ToLower(qr) as query;
  6. 6. Hive snippet CREATE TABLE invites (foo INT, bar STRING) PARTITIONED BY (ds STRING); LOAD DATA LOCAL INPATH './examples/files/kv2.txt' OVERWRITE INTO TABLE invites PARTITION (ds='2008-08-15'); SELECT a.foo FROM invites a WHERE a.ds='2008-08-15'; INSERT OVERWRITE DIRECTORY '/tmp/reg_5' SELECT a.foo, a.bar FROM invites a;
  7. 7. Spark: example val counts = lines.flatMap(line => line.split(“ “)) .map(word => (word, 1)) .reduceByKey(_ + _)
  8. 8. Shark example CREATE TABLE src(key INT, value STRING); LOAD DATA LOCAL INPATH '${env:HIVE_HOME}/examples/files/kv1.txt' INTO TABLE src; SELECT COUNT(1) FROM src; CREATE TABLE src_cached AS SELECT * FROM SRC; SELECT COUNT(1) FROM src_cached;
  9. 9. Disco example def fun_map(line, params): for word in line.split(): yield word, 1 def fun_reduce(iter, params): for word, counts in kvgroup(sorted(iter)): yield word, sum(counts)
  10. 10. Disco driver job = Job().run( input=["http://discoproject.org/media/text/chekhov. txt"], map=map, reduce=reduce) for word, count in result_iterator(job.wait(show=True)): print(word, count)
  11. 11. References I ● “MapReduce: Simplified Data Processing on Large Clusters” Dean, Jeffrey and Ghemawat, Sanjay ● “A Comparison of Join Algorithms for Log Processing in MapReduce” S. Blanas, J. Patel, V. Ercegovac, J. Rao, E. Shekita, Y. Tian ● “Resilient Distributed Datasets: A Fault-Tolerant Abstraction for In-Memory Cluster Computing” Matei Zaharia, Mosharaf Chowdhury, Tathagata Das, Ankur Dave, Justin Ma, Murphy McCauley, Michael J. Franklin, Scott Shenker, Ion Stoica ● “Discretized Streams: An Efficient and Fault-Tolerant Model for Stream Processing on Large Clusters” Matei Zaharia, Tathagata Das, Haoyuan Li, Scott Shenker, Ion Stoica ● “Shark: Fast Data Analysis Using Coarse-grained Distributed Memory” Cliff Engle, Antonio Lupher, Reynold Xin, Matei Zaharia, Haoyuan Li, Scott Shenker, Ion Stoica
  12. 12. References II ● Disco Technical Overview http://disco.readthedocs.org/en/latest/overview.html ● Disco Distributed Filesystem http://disco.readthedocs.org/en/latest/howto/ddfs.html ● An efficient, immutable, persistent mapping object http://discodb.readthedocs. org/en/latest/
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