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new layout: use deterministic randomness for reproducible results

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Alex 2023-09-21 11:21:35 +02:00
parent 013b026d56
commit 3ecc17f8c5
1 changed files with 6 additions and 2 deletions
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8
src/rpc/graph_algo.rs
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@ -1,7 +1,7 @@
//! This module deals with graph algorithms.
//! It is used in layout.rs to build the partition to node assignment.
use rand::prelude::SliceRandom;
use rand::prelude::{SeedableRng, SliceRandom};
use std::cmp::{max, min};
use std::collections::HashMap;
use std::collections::VecDeque;
@ -143,7 +143,11 @@ impl Graph<FlowEdge> {
/// This function shuffles the order of the edge lists. It keeps the ids of the
/// reversed edges consistent.
fn shuffle_edges(&mut self) {
let mut rng = rand::thread_rng();
// We use deterministic randomness so that the layout calculation algorihtm
// will output the same thing every time it is run. This way, the results
// pre-calculated in `garage layout show` will match exactly those used
// in practice with `garage layout apply`
let mut rng = rand::rngs::StdRng::from_seed([0x12u8; 32]);
for i in 0..self.graph.len() {
self.graph[i].shuffle(&mut rng);
// We need to update the ids of the reverse edges.