title: relation between number of input splits and number of mappers in mapreduce hadoop
body: <p>I am a newbie to hadoop and map reduce model and trying to get the concepts right.</p>
  
  <p>I would first like to get concept of input splits and number of mappers correct.</p>
  
  <p>I am running mapreduce wordcount program and following are my questions.</p>
  
  <p>1) How is the input splits determined?
  I ran same program on same cluster with 2 different sized input.</p>
  
  <pre><code>file 1 : size 48mb. =&gt; i got number of splits:1 in log.
  file 2: size 126mb =&gt; number of splits : 1 
  file 2 : size 126mb ( executed in eclipse IDE) =&gt; number of splits: 4
  </code></pre>
  
  <p>should not be the number of splits equal to 2 for the 126 mb file? Becuase I have read that the block size is 64 MB. so it would have to create 2 splits.</p>
  
  <p>2) How is number of mappers determined? I am trying to get number of mappers to understand the workflow of mapreduce through following line.</p>
  
  <pre><code>conf.get("mapred.map.tasks")
  </code></pre>
  
  <p>It returns 2 everytime . </p>
  
  <p>3) is there any relation between number of splits and number of mappers?</p>
  
  <p>4) do above things depends on the cluster ? is it same for pseudo distributed mode and other cluster or different?</p>
  
  <p>Thank you.</p>