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par_sort_graph: Simplify using Rayon #150

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75 changes: 32 additions & 43 deletions webgraph/src/utils/par_sort_graph.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -12,7 +12,6 @@
use std::marker::PhantomData;
use std::num::NonZeroUsize;
use std::path::Path;
use std::sync::Mutex;

use anyhow::{ensure, Context, Result};
use dsi_bitstream::traits::NE;
Expand Down Expand Up @@ -281,30 +280,27 @@ impl<L> ParSortGraph<L> {
let presort_tmp_dir =
tempfile::tempdir().context("Could not create temporary directory")?;

let unsorted_pairs = unsorted_pairs.into_iter();
let num_blocks = unsorted_pairs.len();
let presort_tmp_dir = &presort_tmp_dir;

let partitioned_presorted_pairs = Mutex::new(vec![Vec::new(); num_blocks]);

std::thread::scope(|s| {
let partitioned_presorted_pairs = &partitioned_presorted_pairs;
let presort_tmp_dir = &presort_tmp_dir;
for (block_id, pair) in unsorted_pairs.enumerate() {
let deserializer = deserializer.clone();
let mut pl = pl.clone();
s.spawn(move || {
let partitioned_presorted_pairs = unsorted_pairs
.into_iter()
.enumerate()
.par_bridge()
.map_init(
|| (deserializer.clone(), pl.clone()),
|(deserializer, pl), (block_id, pair)| {
let mut unsorted_buffers = (0..num_partitions)
.map(|_| Vec::with_capacity(batch_size))
.collect::<Vec<_>>();
let mut sorted_pairs =
(0..num_partitions).map(|_| Vec::new()).collect::<Vec<_>>();

for (src, dst, label) in pair {
/* ensure!(
ensure!(
src < self.num_nodes,
"Expected {}, but got {src}",
self.num_nodes
); */
);
let partition_id = src / num_nodes_per_partition;

let sorted_pairs = &mut sorted_pairs[partition_id];
Expand All @@ -320,8 +316,7 @@ impl<L> ParSortGraph<L> {
sorted_pairs,
buf,
)
.context("Could not flush buffer")
.unwrap();
.context("Could not flush buffer")?;
assert!(buf.is_empty(), "flush_buffer did not empty the buffer");
pl.update_with_count(buf_len);
}
Expand All @@ -347,43 +342,37 @@ impl<L> ParSortGraph<L> {
&mut pairs,
&mut buf,
)
.context("Could not flush buffer at the end")
.unwrap();
.context("Could not flush buffer at the end")?;
assert!(buf.is_empty(), "flush_buffer did not empty the buffer");
pl.update_with_count(buf_len);
}

// TODO: ugly
partitioned_presorted_pairs.lock().unwrap()[block_id] = sorted_pairs;
});
}
});
Ok(sorted_pairs)
},
)
.collect::<Result<Vec<_>>>()?;

// At this point, the iterator could be collected into
// {worker_id -> {partition_id -> [iterators]}}
// ie. Vec<Vec<Vec<BatchIterator>>>>.
//
// Let's merge the {partition_id -> [iterators]} maps of each worker
let partitioned_presorted_pairs = partitioned_presorted_pairs
.into_inner()
.unwrap()
.into_par_iter()
.reduce(
|| (0..num_partitions).map(|_| Vec::new()).collect(),
|mut pair_partitions1: Vec<Vec<BatchIterator<D>>>,
pair_partitions2: Vec<Vec<BatchIterator<D>>>|
-> Vec<Vec<BatchIterator<D>>> {
assert_eq!(pair_partitions1.len(), num_partitions);
assert_eq!(pair_partitions2.len(), num_partitions);
for (partition1, partition2) in pair_partitions1
.iter_mut()
.zip(pair_partitions2.into_iter())
{
partition1.extend(partition2.into_iter());
}
pair_partitions1
},
);
let partitioned_presorted_pairs = partitioned_presorted_pairs.into_par_iter().reduce(
|| (0..num_partitions).map(|_| Vec::new()).collect(),
|mut pair_partitions1: Vec<Vec<BatchIterator<D>>>,
pair_partitions2: Vec<Vec<BatchIterator<D>>>|
-> Vec<Vec<BatchIterator<D>>> {
assert_eq!(pair_partitions1.len(), num_partitions);
assert_eq!(pair_partitions2.len(), num_partitions);
for (partition1, partition2) in pair_partitions1
.iter_mut()
.zip(pair_partitions2.into_iter())
{
partition1.extend(partition2.into_iter());
}
pair_partitions1
},
);
// At this point, the iterator was turned into
// {partition_id -> [iterators]}
// ie. Vec<Vec<BatchIterator>>>.
Expand Down
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