void VariableWindowDataSet::Pop() {
auto& transaction = Front();
if (first_chunk_start_offset + 1 < chunk_size) {
// Update the inverted index to clear the bits set corresponding to
// the items in this transaction.
auto offset = transaction.id - first_chunk_start_tid;
ASSERT(offset == first_chunk_start_offset);
ASSERT((offset / chunk_size) == 0); // Should be first chunk.
auto bit_num = offset % chunk_size;
for (uint32_t i = 0; i < transaction.items.size(); i++) {
Item item = transaction.items[i];
// Assert that the bit was actually set first!
ASSERT(index[item.GetIndex()][0][bit_num] == true);
index[item.GetIndex()][0].set(bit_num, false);
}
first_chunk_start_offset++;
} else {
// We're removing the last transaction in the first chunk/bitset. We
// must drop every tidlist's first chunk.
for (uint32_t i = 0; i < index.size(); i++) {
TidList& tidlist = index[i];
if (tidlist.size() > 0) {
// Some tid lists can be empty if the corresponding item only appeared
// in blocks that have already been purged.
tidlist.erase(tidlist.begin(), tidlist.begin() + 1);
}
}
first_chunk_start_offset = 0;
first_chunk_start_tid += chunk_size;
}
transactions.pop_front();
}
int VariableWindowDataSet::Count(const ItemSet& aItemSet) const {
auto& items = aItemSet.mItems;
// Find item with the shortest tidlist.
auto itr = items.begin();
Item smallest_item = *itr;
// Note: We do not increment iterator, so we do the existence in the
// loop check below.
for (; itr != items.end(); itr++) {
Item item = *itr;
if (item.GetIndex() >= index.size()) {
// Item does not exist in itemset, so it will have 0 count.
return 0;
}
if (index[item.GetIndex()].size() < index[smallest_item.GetIndex()].size()) {
smallest_item = item;
}
}
// AND the shortest tidlist with all other item's tidlists, and count that.
size_t count = 0;
const TidList& shortest = index[smallest_item.GetIndex()];
for (uint32_t i = 0; i < shortest.size(); i++) {
bitset<chunk_size> b(shortest[i]);
if (b.none()) {
// No bits set in this chunk, no point iterating over other chunks, as
// the result will be 0 when we AND with them.
continue;
}
for (auto itr = items.begin(); itr != items.end(); itr++) {
if (*itr == smallest_item) {
continue;
}
const TidList& other = index[itr->GetIndex()];
if (i < other.size()) {
b &= other[i];
}
}
count += b.count();
}
return (int)count;
}
int VariableWindowDataSet::Count(const Item& aItem) const {
auto item_idx = aItem.GetIndex();
if (item_idx >= index.size()) {
return 0;
}
const TidList& tidlist = index.at(item_idx);
size_t count = 0;
for (auto i = 0; i < tidlist.size(); i++) {
const std::bitset<chunk_size>& b = tidlist[i];
count += b.count();
}
return (int)count;
}