@Test
public void itShouldDecompressLists() throws IOException {
final Input input =
getInput(
"1 1 01101 00101 0101 01100 1"
+ "0100 1 1 1 01101 00001 1 1 00100011"
+ "0101 1 1 1 1"
+ "1 0100 00001 001000111"
+ "0101 1 1 1 1"
+ "01101 0101 0 0101 01100 1 1");
final PebbleOffsetsStore offsetsStore =
new LongListPebbleOffsetsStore(new long[] {0L, 22L, 49L, 57L, 76L, 84L});
final PebbleBytesStore bytesStore = new BytesArrayPebbleBytesStore(input.buffer, offsetsStore);
final int valueBitSize = 5;
final LongList[] expectedLists =
new LongList[] {
new LongArrayList(new long[] {5L, 8L, 12L, 13L}),
new LongArrayList(new long[] {1L, 2L, 3L, 5L, 8L, 12L, 13L, 14L}),
new LongArrayList(new long[] {5L, 8L, 12L, 13L}),
new LongArrayList(
new long[] {1L, 2L, 3L, 4L, 5L, 6L, 7L, 8L, 9L, 10L, 11L, 12L, 13L, 14L}),
new LongArrayList(new long[] {5L, 8L, 12L, 13L}),
new LongArrayList(new long[] {5L, 8L, 12L, 13L})
};
final LongList[] lists = new LongList[expectedLists.length];
LongList list;
LongIterator iterator;
for (int i = 0; i < lists.length; i++) {
iterator = StrictlyIncrementalListIterator.build(i, valueBitSize, bytesStore);
lists[i] = list = new LongArrayList();
while (iterator.hasNext()) {
list.add(iterator.nextLong());
}
}
assertEquals(
Helper.<Long, LongList>translateToUtilsCollection(expectedLists),
Helper.<Long, LongList>translateToUtilsCollection(lists));
}
public double measureUser(
TestUser user, MeanAccumulator context, List<ScoredId> recommendations, int listSize) {
if (recommendations.size() > listSize) {
recommendations = new ArrayList<ScoredId>(recommendations.subList(0, listSize));
}
SparseVector ratings = user.getTestRatings();
LongList ideal = ratings.keysByValue(true);
if (ideal.size() > listSize) {
ideal = ideal.subList(0, listSize);
}
double idealGain = computeDCG(ideal, ratings);
LongList actual = new LongArrayList(recommendations.size());
for (ScoredId id : recommendations) {
actual.add(id.getId());
}
double gain = computeDCG(actual, ratings);
double score = gain / idealGain;
context.add(score);
return score;
}
/** Compute the DCG of a list of items with respect to a value vector. */
static double computeDCG(LongList items, SparseVector values) {
final double lg2 = log(2);
double gain = 0;
int rank = 0;
LongIterator iit = items.iterator();
while (iit.hasNext()) {
final long item = iit.nextLong();
final double v = values.get(item, 0);
rank++;
if (rank < 2) {
gain += v;
} else {
gain += v * lg2 / log(rank);
}
}
return gain;
}
private static void doSwap(LongList longs, int i, int j) {
longs.set(i, longs.set(j, longs.get(i)));
}