How can I pass additional data to the Mapper?
<p>Since some data are shared among all the <code>map()</code> functions, I can't generate them in the setup(), since each <code>setup()</code> corresponds to each <code>map()</code> function, and what I want to do is to pre-produce some data and store it somewhere achievable, then use it in each <code>map()</code>.</p>

<p>How can I possibly do it? Say I am doing KNN with Mapreduce, and I want to use all of the test data by each <code>map()</code>. Where should I store those test data and then use them in the mapper?</p>

<p>Thank you so much.</p>