/**
* Load preferences from an input stream.
*
* <p>Each line is a different preference, with tab-separated fields indicating user, item, weight
* and other information.
*
* @param <U> type of the users
* @param <I> type of the items
* @param in input stream to read from
* @param uParser user type parser
* @param iParser item type parser
* @param dp double parse
* @param uIndex user index
* @param iIndex item index
* @return a simple list-of-lists FastPreferenceData with the information read
* @throws IOException when path does not exists of IO error
*/
public static <U, I> SimpleFastPreferenceData<U, I> load(
InputStream in,
Parser<U> uParser,
Parser<I> iParser,
DoubleParser dp,
FastUserIndex<U> uIndex,
FastItemIndex<I> iIndex)
throws IOException {
AtomicInteger numPreferences = new AtomicInteger();
List<List<IdxPref>> uidxList = new ArrayList<>();
for (int uidx = 0; uidx < uIndex.numUsers(); uidx++) {
uidxList.add(null);
}
List<List<IdxPref>> iidxList = new ArrayList<>();
for (int iidx = 0; iidx < iIndex.numItems(); iidx++) {
iidxList.add(null);
}
try (BufferedReader reader = new BufferedReader(new InputStreamReader(in))) {
reader
.lines()
.forEach(
l -> {
CharSequence[] tokens = split(l, '\t', 4);
U user = uParser.parse(tokens[0]);
I item = iParser.parse(tokens[1]);
double value;
if (tokens.length >= 3) {
value = dp.parse(tokens[2]);
} else {
value = dp.parse(null);
}
int uidx = uIndex.user2uidx(user);
int iidx = iIndex.item2iidx(item);
numPreferences.incrementAndGet();
List<IdxPref> uList = uidxList.get(uidx);
if (uList == null) {
uList = new ArrayList<>();
uidxList.set(uidx, uList);
}
uList.add(new IdxPref(iidx, value));
List<IdxPref> iList = iidxList.get(iidx);
if (iList == null) {
iList = new ArrayList<>();
iidxList.set(iidx, iList);
}
iList.add(new IdxPref(uidx, value));
});
}
return new SimpleFastPreferenceData<>(
numPreferences.intValue(), uidxList, iidxList, uIndex, iIndex);
}
@Override
public int item2iidx(I i) {
return iIndex.item2iidx(i);
}