ImmutableMap.Builder<Symbol, DoubleList> cbld = ImmutableMap.builder();
for (ChannelStorage chan: channels.values()) {
DoubleArrayList built;
if (reuse) {
built = chan.values;
built.trim();
} else {
built = new DoubleArrayList(chan.values);
}
cbld.put(chan.symbol, built);
}