SAMFileReader r1 = new SAMFileReader(params.file1);
SAMFileReader r2 = new SAMFileReader(params.file2);
SAMRecordIterator it1, it2;
if (params.location != null) {
AlignmentSliceQuery query = new AlignmentSliceQuery(params.location);
if (SAMRecord.NO_ALIGNMENT_REFERENCE_NAME.equals(query.sequence)) {
it1 = r1.queryUnmapped();
it2 = r2.queryUnmapped();
} else {
it1 = r1.queryContained(query.sequence, query.start, query.end);