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Fix segment reconstruction #1850

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merged 3 commits into from
Aug 21, 2023
Merged

Fix segment reconstruction #1850

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a2d0d0b
Fix segment/piece reconstruction when all source pieces are present
nazar-pc Aug 20, 2023
129883a
Remove unnecessary preference of source pieces
nazar-pc Aug 20, 2023
b6b467c
Move the check for piece index to earlier
nazar-pc Aug 20, 2023
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100 changes: 36 additions & 64 deletions crates/subspace-archiving/src/piece_reconstructor.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -77,73 +77,45 @@ impl PiecesReconstructor {
) -> Result<(ArchivedHistorySegment, Polynomial), ReconstructorError> {
let mut reconstructed_pieces = ArchivedHistorySegment::default();

if !input_pieces
.iter()
// Take each source shards here
.step_by(2)
.zip(
reconstructed_pieces
.iter_mut()
.map(|piece| piece.record_mut().iter_mut()),
)
.all(|(maybe_piece, raw_record)| {
if let Some(piece) = maybe_piece {
piece
.record()
.iter()
.zip(raw_record)
.for_each(|(source, target)| {
*target = *source;
});
true
} else {
false
}
})
{
// If not all data pieces are available, need to reconstruct data shards using erasure
// coding.

// Scratch buffer to avoid re-allocation
let mut tmp_shards_scalars =
Vec::<Option<Scalar>>::with_capacity(ArchivedHistorySegment::NUM_PIECES);
// Iterate over the chunks of `Scalar::SAFE_BYTES` bytes of all records
for record_offset in 0..RawRecord::SIZE / Scalar::SAFE_BYTES {
// Collect chunks of each record at the same offset
for maybe_piece in input_pieces.iter() {
let maybe_scalar = maybe_piece
.as_ref()
.map(|piece| {
piece
.record()
.iter()
.nth(record_offset)
.expect("Statically guaranteed to exist in a piece; qed")
})
.map(Scalar::try_from)
.transpose()
.map_err(ReconstructorError::DataShardsReconstruction)?;

tmp_shards_scalars.push(maybe_scalar);
}

self.erasure_coding
.recover(&tmp_shards_scalars)
.map_err(ReconstructorError::DataShardsReconstruction)?
.into_iter()
.zip(reconstructed_pieces.iter_mut().map(|piece| {
// Scratch buffer to avoid re-allocation
let mut tmp_shards_scalars =
Vec::<Option<Scalar>>::with_capacity(ArchivedHistorySegment::NUM_PIECES);
// Iterate over the chunks of `Scalar::SAFE_BYTES` bytes of all records
for record_offset in 0..RawRecord::SIZE / Scalar::SAFE_BYTES {
// Collect chunks of each record at the same offset
for maybe_piece in input_pieces.iter() {
let maybe_scalar = maybe_piece
.as_ref()
.map(|piece| {
piece
.record_mut()
.iter_mut()
.record()
.iter()
.nth(record_offset)
.expect("Statically guaranteed to exist in a piece; qed")
}))
.for_each(|(source_scalar, segment_data)| {
segment_data.copy_from_slice(&source_scalar.to_bytes());
});
})
.map(Scalar::try_from)
.transpose()
.map_err(ReconstructorError::DataShardsReconstruction)?;

tmp_shards_scalars.clear();
tmp_shards_scalars.push(maybe_scalar);
}

self.erasure_coding
.recover(&tmp_shards_scalars)
.map_err(ReconstructorError::DataShardsReconstruction)?
.into_iter()
.zip(reconstructed_pieces.iter_mut().map(|piece| {
piece
.record_mut()
.iter_mut()
.nth(record_offset)
.expect("Statically guaranteed to exist in a piece; qed")
}))
.for_each(|(source_scalar, segment_data)| {
segment_data.copy_from_slice(&source_scalar.to_bytes());
});

tmp_shards_scalars.clear();
}

let source_record_commitments = {
Expand Down Expand Up @@ -257,12 +229,12 @@ impl PiecesReconstructor {
segment_pieces: &[Option<Piece>],
piece_position: usize,
) -> Result<Piece, ReconstructorError> {
let (reconstructed_records, polynomial) = self.reconstruct_shards(segment_pieces)?;

if piece_position >= ArchivedHistorySegment::NUM_PIECES {
return Err(ReconstructorError::IncorrectPiecePosition);
}

let (reconstructed_records, polynomial) = self.reconstruct_shards(segment_pieces)?;

let mut piece = Piece::from(&reconstructed_records[piece_position]);

piece.witness_mut().copy_from_slice(
Expand Down
4 changes: 2 additions & 2 deletions crates/subspace-archiving/tests/integration/piece_reconstruction.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -78,8 +78,8 @@ fn piece_reconstruction_works() {
let missing_pieces = maybe_pieces
.iter_mut()
.enumerate()
.skip(100)
.take(40)
.skip(120)
.take(10)
.map(|(piece_position, piece)| (piece_position, piece.take().unwrap()))
.collect::<Vec<_>>();

Expand Down
2 changes: 1 addition & 1 deletion crates/subspace-farmer-components/src/segment_reconstruction.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -37,7 +37,7 @@ pub(crate) async fn recover_missing_piece<PG: PieceGetter>(
let required_pieces_number = RecordedHistorySegment::NUM_RAW_RECORDS;

let mut received_segment_pieces = segment_index
.segment_piece_indexes_source_first()
.segment_piece_indexes()
.map(|piece_index| async move {
let _permit = match semaphore.acquire().await {
Ok(permit) => permit,
Expand Down