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use hashbrown::hash_map::Entry;
use polars_utils::hashing::{DirtyHash, hash_to_partition};
use polars_utils::idx_vec::IdxVec;
use polars_utils::itertools::Itertools;
use polars_utils::sync::SyncPtr;
use polars_utils::total_ord::{ToTotalOrd, TotalHash, TotalOrdWrap};
use polars_utils::unitvec;
use rayon::prelude::*;
use crate::POOL;
use crate::hashing::*;
use crate::prelude::*;
use crate::utils::flatten;
fn get_init_size() -> usize {
// we check if this is executed from the main thread
// we don't want to pre-allocate this much if executed
// group_tuples in a parallel iterator as that explodes allocation
if POOL.current_thread_index().is_none() {
_HASHMAP_INIT_SIZE
} else {
0
}
}
fn finish_group_order(mut out: Vec<Vec<IdxItem>>, sorted: bool) -> GroupsType {
if sorted {
// we can just take the first value, no need to flatten
let mut out = if out.len() == 1 {
out.pop().unwrap()
} else {
let (cap, offsets) = flatten::cap_and_offsets(&out);
// we write (first, all) tuple because of sorting
let mut items = Vec::with_capacity(cap);
let items_ptr = unsafe { SyncPtr::new(items.as_mut_ptr()) };
POOL.install(|| {
out.into_par_iter()
.zip(offsets)
.for_each(|(mut g, offset)| {
// pre-sort every array
// this will make the final single threaded sort much faster
g.sort_unstable_by_key(|g| g.0);
unsafe {
let mut items_ptr: *mut (IdxSize, IdxVec) = items_ptr.get();
items_ptr = items_ptr.add(offset);
for (i, g) in g.into_iter().enumerate() {
std::ptr::write(items_ptr.add(i), g)
}
}
});
});
unsafe {
items.set_len(cap);
}
items
};
out.sort_unstable_by_key(|g| g.0);
let mut idx = GroupsIdx::from_iter(out);
idx.sorted = true;
GroupsType::Idx(idx)
} else {
// we can just take the first value, no need to flatten
if out.len() == 1 {
GroupsType::Idx(GroupsIdx::from(out.pop().unwrap()))
} else {
// flattens
GroupsType::Idx(GroupsIdx::from(out))
}
}
}
pub(crate) fn group_by<K>(keys: impl Iterator<Item = K>, sorted: bool) -> GroupsType
where
K: TotalHash + TotalEq,
{
let init_size = get_init_size();
let (mut first, mut groups);
if sorted {
groups = Vec::with_capacity(get_init_size());
first = Vec::with_capacity(get_init_size());
let mut hash_tbl = PlHashMap::with_capacity(init_size);
for (idx, k) in keys.enumerate_idx() {
match hash_tbl.entry(TotalOrdWrap(k)) {
Entry::Vacant(entry) => {
let group_idx = groups.len() as IdxSize;
entry.insert(group_idx);
groups.push(unitvec![idx]);
first.push(idx);
},
Entry::Occupied(entry) => unsafe {
groups.get_unchecked_mut(*entry.get() as usize).push(idx)
},
}
}
} else {
let mut hash_tbl = PlHashMap::with_capacity(init_size);
for (idx, k) in keys.enumerate_idx() {
match hash_tbl.entry(TotalOrdWrap(k)) {
Entry::Vacant(entry) => {
entry.insert((idx, unitvec![idx]));
},
Entry::Occupied(mut entry) => entry.get_mut().1.push(idx),
}
}
(first, groups) = hash_tbl.into_values().unzip();
}
GroupsType::Idx(GroupsIdx::new(first, groups, sorted))
}
// giving the slice info to the compiler is much
// faster than the using an iterator, that's why we
// have the code duplication
pub(crate) fn group_by_threaded_slice<T, IntoSlice>(
keys: Vec<IntoSlice>,
n_partitions: usize,
sorted: bool,
) -> GroupsType
where
T: ToTotalOrd,
<T as ToTotalOrd>::TotalOrdItem: Send + Sync + Copy + DirtyHash,
IntoSlice: AsRef<[T]> + Send + Sync,
{
let init_size = get_init_size();
// We will create a hashtable in every thread.
// We use the hash to partition the keys to the matching hashtable.
// Every thread traverses all keys/hashes and ignores the ones that doesn't fall in that partition.
let out = POOL.install(|| {
(0..n_partitions)
.into_par_iter()
.map(|thread_no| {
let mut hash_tbl = PlHashMap::with_capacity(init_size);
let mut offset = 0;
for keys in &keys {
let keys = keys.as_ref();
let len = keys.len() as IdxSize;
for (key_idx, k) in keys.iter().enumerate_idx() {
let k = k.to_total_ord();
let idx = key_idx + offset;
if thread_no == hash_to_partition(k.dirty_hash(), n_partitions) {
match hash_tbl.entry(k) {
Entry::Vacant(entry) => {
entry.insert((idx, unitvec![idx]));
},
Entry::Occupied(mut entry) => {
entry.get_mut().1.push(idx);
},
}
}
}
offset += len;
}
hash_tbl
.into_iter()
.map(|(_k, v)| v)
.collect_trusted::<Vec<_>>()
})
.collect::<Vec<_>>()
});
finish_group_order(out, sorted)
}
pub(crate) fn group_by_threaded_iter<T, I>(
keys: &[I],
n_partitions: usize,
sorted: bool,
) -> GroupsType
where
I: IntoIterator<Item = T> + Send + Sync + Clone,
I::IntoIter: ExactSizeIterator,
T: ToTotalOrd,
<T as ToTotalOrd>::TotalOrdItem: Send + Sync + Copy + DirtyHash,
{
let init_size = get_init_size();
// We will create a hashtable in every thread.
// We use the hash to partition the keys to the matching hashtable.
// Every thread traverses all keys/hashes and ignores the ones that doesn't fall in that partition.
let out = POOL.install(|| {
(0..n_partitions)
.into_par_iter()
.map(|thread_no| {
let mut hash_tbl: PlHashMap<T::TotalOrdItem, IdxVec> =
PlHashMap::with_capacity(init_size);
let mut offset = 0;
for keys in keys {
let keys = keys.clone().into_iter();
let len = keys.len() as IdxSize;
for (key_idx, k) in keys.into_iter().enumerate_idx() {
let k = k.to_total_ord();
let idx = key_idx + offset;
if thread_no == hash_to_partition(k.dirty_hash(), n_partitions) {
match hash_tbl.entry(k) {
Entry::Vacant(entry) => {
entry.insert(unitvec![idx]);
},
Entry::Occupied(mut entry) => {
entry.get_mut().push(idx);
},
}
}
}
offset += len;
}
// iterating the hash tables locally
// was faster than iterating in the materialization phase directly
// the proper end vec. I believe this is because the hash-table
// currently is local to the thread so in hot cache
// So we first collect into a tight vec and then do a second
// materialization run
// this is also faster than the index-map approach where we
// directly locally store to a vec at the cost of an extra
// indirection
hash_tbl
.into_iter()
.map(|(_k, v)| (unsafe { *v.first().unwrap_unchecked() }, v))
.collect_trusted::<Vec<_>>()
})
.collect::<Vec<_>>()
});
finish_group_order(out, sorted)
}