add delegation logic to transition crate

beacon_chain/transition/src/delegation/block_hash.rs

@@ -0,0 +1,62 @@
+use super::utils::errors::ParameterError;
+use super::utils::types::Hash256;
+
+/*
+ * Work-in-progress function: not ready for review.
+ */
+
+pub fn get_block_hash(
+    active_state_recent_block_hashes: &[Hash256],
+    current_block_slot: u64,
+    slot: u64,
+    cycle_length: u64, // convert from standard u8
+) -> Result<Hash256, ParameterError> {
+    // active_state must have at 2*cycle_length hashes
+    assert_error!(
+        active_state_recent_block_hashes.len() as u64 == cycle_length * 2,
+        ParameterError::InvalidInput(String::from(
+            "active state has incorrect number of block hashes"
+        ))
+    );
+
+    let state_start_slot = (current_block_slot)
+        .checked_sub(cycle_length * 2)
+        .unwrap_or(0);
+
+    assert_error!(
+        (state_start_slot <= slot) && (slot < current_block_slot),
+        ParameterError::InvalidInput(String::from("incorrect slot number"))
+    );
+
+    let index = 2 * cycle_length + slot - current_block_slot; // should always be positive
+    Ok(active_state_recent_block_hashes[index as usize])
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_get_block_hash() {
+        let block_slot: u64 = 10;
+        let slot: u64 = 3;
+        let cycle_length: u64 = 8;
+
+        let mut block_hashes: Vec<Hash256> = Vec::new();
+        for _i in 0..2 * cycle_length {
+            block_hashes.push(Hash256::random());
+        }
+
+        let result = get_block_hash(
+            &block_hashes,
+            block_slot,
+            slot,
+            cycle_length)
+            .unwrap();
+
+        assert_eq!(
+            result,
+            block_hashes[(2 * cycle_length + slot - block_slot) as usize]
+        );
+    }
+}

beacon_chain/transition/src/delegation/mod.rs

@@ -0,0 +1,6 @@
+use super::types;
+use super::TransitionError;
+use super::shuffling::shuffle;
+
+// mod block_hash;
+pub mod validator;

beacon_chain/transition/src/delegation/validator.rs

@@ -0,0 +1,232 @@
+use super::types::{ShardAndCommittee, ValidatorRecord, ChainConfig};
+use super::TransitionError;
+use super::shuffle;
+
+type DelegatedSlot = Vec<ShardAndCommittee>;
+type DelegatedCycle = Vec<DelegatedSlot>;
+
+
+/* Produce a vector of validators indicies where those validators start and end
+ * dynasties are within the supplied `dynasty`.
+*/
+fn active_validator_indicies(
+    dynasty: &u64,
+    validators: &Vec<ValidatorRecord>)
+    -> Vec<usize>
+{
+    validators.iter()
+        .enumerate()
+        .filter_map(|(i, validator)| {
+            if (validator.start_dynasty >= *dynasty) &
+                (validator.end_dynasty < *dynasty)
+            {
+                Some(i)
+            } else {
+                None
+            }
+        })
+        .collect()
+}
+
+
+/*
+ * Delegates active validators into slots for a given cycle, given a random seed.
+ * Returns a vector or ShardAndComitte vectors representing the shards and committiees for
+ * each slot.
+ * References get_new_shuffling (ethereum 2.1 specification)
+ */
+pub fn delegate_validators(
+    seed: &[u8],
+    validators: &Vec<ValidatorRecord>,
+    dynasty: &u64,
+    crosslinking_shard_start: &u16,
+    config: &ChainConfig)
+    -> Result<DelegatedCycle, TransitionError>
+{
+    let shuffled_validator_indices = {
+        let mut validator_indices = active_validator_indicies(dynasty, validators);
+        match shuffle(seed, validator_indices) {
+            Ok(shuffled) => shuffled,
+            _ => return Err(TransitionError::InvalidInput(
+                    String::from("Shuffle list length exceed.")))
+        }
+    };
+    let shard_indices = (0_usize..config.shard_count as usize).into_iter().collect();
+    let crosslinking_shard_start = *crosslinking_shard_start as usize;
+    let cycle_length = config.cycle_length as usize;
+    let min_committee_size = config.min_committee_size as usize;
+    generate_cycle(
+        &shuffled_validator_indices,
+        &shard_indices,
+        &crosslinking_shard_start,
+        &cycle_length,
+        &min_committee_size)
+}
+
+/*
+ * Given the validator list, delegates the validators into slots and comittees for a given cycle.
+ */
+fn generate_cycle(
+    validator_indices: &Vec<usize>,
+    shard_indices: &Vec<usize>,
+    crosslinking_shard_start: &usize,
+    cycle_length: &usize,
+    min_committee_size: &usize)
+    -> Result<DelegatedCycle, TransitionError>
+{
+    let validator_count = validator_indices.len();
+    let shard_count = shard_indices.len();
+
+    let (committees_per_slot, slots_per_committee) = {
+        if validator_count >= cycle_length * min_committee_size {
+            let committees_per_slot = validator_count / cycle_length / (min_committee_size * 2) + 1;
+            let slots_per_committee = 1;
+            (committees_per_slot, slots_per_committee)
+        } else {
+            let committees_per_slot = 1;
+            let mut slots_per_committee = 1;
+            while (validator_count * slots_per_committee < cycle_length * min_committee_size) &
+                (slots_per_committee < *cycle_length) {
+                slots_per_committee = slots_per_committee * 2;
+            }
+            (committees_per_slot, slots_per_committee)
+        }
+    };
+
+    let cycle = validator_indices
+        .chunks(validator_indices.len() / *cycle_length)
+        .enumerate()
+        .map(|(i, slot_indices)| {
+            let shard_id_start = crosslinking_shard_start + i * committees_per_slot / slots_per_committee;
+            return slot_indices
+                .chunks(slot_indices.len() / committees_per_slot)
+                .enumerate()
+                .map(|(j, shard_indices)| {
+                    return ShardAndCommittee{
+                        shard_id: ((shard_id_start + j) % shard_count) as u16,
+                        committee: shard_indices.to_vec(),
+                    }
+                })
+                .collect()
+        })
+        .collect();
+    Ok(cycle)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn generate_cycle_helper(
+        validator_count: &usize,
+        shard_count: &usize,
+        crosslinking_shard_start: &usize,
+        cycle_length: &usize,
+        min_committee_size: &usize)
+        -> (Vec<usize>, Vec<usize>, Result<DelegatedCycle, TransitionError>)
+    {
+        let validator_indices = (0_usize..*validator_count).into_iter().collect();
+        let shard_indices = (0_usize..*shard_count).into_iter().collect();
+        let result = generate_cycle(
+            &validator_indices,
+            &shard_indices,
+            &crosslinking_shard_start,
+            &cycle_length,
+            &min_committee_size);
+        (validator_indices, shard_indices, result)
+    }
+
+    #[allow(dead_code)]
+    fn print_cycle(cycle: &DelegatedCycle) {
+        cycle.iter()
+            .enumerate()
+            .for_each(|(i, slot)| {
+                println!("slot {:?}", &i);
+                slot.iter()
+                    .enumerate()
+                    .for_each(|(i, sac)| {
+                        println!("#{:?}\tshard_id={}\tcommittee.len()={}",
+                            &i, &sac.shard_id, &sac.committee.len())
+                    })
+            });
+    }
+
+    fn flatten_validators(cycle: &DelegatedCycle)
+        -> Vec<usize>
+    {
+        let mut flattened = vec![];
+        for slot in cycle.iter() {
+            for sac in slot.iter() {
+                for validator in sac.committee.iter() {
+                    flattened.push(*validator);
+                }
+            }
+        }
+        flattened
+    }
+
+    fn flatten_and_dedup_shards(cycle: &DelegatedCycle)
+        -> Vec<usize>
+    {
+        let mut flattened = vec![];
+        for slot in cycle.iter() {
+            for sac in slot.iter() {
+                flattened.push(sac.shard_id as usize);
+            }
+        }
+        flattened.dedup();
+        flattened
+    }
+
+    fn flatten_shards_in_slots(cycle: &DelegatedCycle)
+        -> Vec<Vec<usize>>
+    {
+        let mut shards_in_slots: Vec<Vec<usize>> = vec![];
+        for slot in cycle.iter() {
+            let mut shards: Vec<usize> = vec![];
+            for sac in slot.iter() {
+                shards.push(sac.shard_id as usize);
+            }
+            shards_in_slots.push(shards);
+        }
+        shards_in_slots
+    }
+
+
+    #[test]
+    fn test_generate_cycle() {
+        let validator_count: usize = 100;
+        let shard_count: usize = 10;
+        let crosslinking_shard_start: usize = 0;
+        let cycle_length: usize = 20;
+        let min_committee_size: usize = 10;
+        let (validators, shards, result) = generate_cycle_helper(
+            &validator_count,
+            &shard_count,
+            &crosslinking_shard_start,
+            &cycle_length,
+            &min_committee_size);
+        let cycle = result.unwrap();
+
+        let assigned_validators = flatten_validators(&cycle);
+        let assigned_shards = flatten_and_dedup_shards(&cycle);
+        let shards_in_slots = flatten_shards_in_slots(&cycle);
+        assert_eq!(assigned_validators, validators, "Validator assignment incorrect");
+        assert_eq!(assigned_shards, shards, "Shard assignment incorrect");
+
+        let expected_shards_in_slots: Vec<Vec<usize>> = vec![
+            vec![0], vec![0],   // Each line is 2 slots..
+            vec![1], vec![1],
+            vec![2], vec![2],
+            vec![3], vec![3],
+            vec![4], vec![4],
+            vec![5], vec![5],
+            vec![6], vec![6],
+            vec![7], vec![7],
+            vec![8], vec![8],
+            vec![9], vec![9],
+        ];
+        // assert!(compare_shards_in_slots(&cycle, &expected_shards_in_slots));
+        assert_eq!(expected_shards_in_slots, shards_in_slots, "Shard assignment incorrect.")
+    }
+}