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If you follow the previous example, Each bsp processor will send a bundle of thousand Integer messages to a masterTask. Instead, you could use a Combiners in your BSP program to perform a sum Integer messages and to write more concise and maintainable as below, that is what the Combiners are usefulwhy you use Combiners.
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public static class SumCombiner extends Combiner { @Override public BSPMessageBundle combine(Iterable<BSPMessage> messages) { BSPMessageBundle bundle = new BSPMessageBundle(); int sum = 0; Iterator<BSPMessage> it = messages.iterator(); while (it.hasNext()) { sum += ((IntegerMessage) it.next()).getData(); } bundle.addMessage(new IntegerMessage("Sum", sum)); return bundle; } } |