private final DoubleBigArray sums;
public DoubleSumGroupedAccumulator(int valueChannel, Optional<Integer> maskChannel, Optional<Integer> sampleWeightChannel)
{
super(valueChannel, SINGLE_DOUBLE, SINGLE_DOUBLE, maskChannel, sampleWeightChannel);
this.notNull = new BooleanBigArray();
this.sums = new DoubleBigArray();
}