final Map<SNPCallPair, TreeMap<Integer, Long>> calltable_validation = new HashMap<SNPCallPair, TreeMap<Integer, Long>>();
ReferenceSequence reference = null;
while ((reference = reference_file.nextSequence()) != null) {
for (SamPositionIterator position_iterator : positionIterators) {
position_iterator.nextSequence();
String ref_name = reference.getName();
if (!position_iterator.getCurrentSequence().equals(ref_name))