closeables.addFirst(rhatInput);
outputs = new MultipleOutputs(new JobConf(context.getConfiguration()));
closeables.addFirst(new IOUtils.MultipleOutputsCloseableAdapter(outputs));
qr = new QRLastStep(qhatInput, rhatInput, blockNum);
closeables.addFirst(qr);
/*
* it's so happens that current QRLastStep's implementation preloads R
* sequence into memory in the constructor so it's ok to close rhat input
* now.