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Try new way to do it.

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This commit is contained in:
chriseth 2022-09-12 17:47:52 +02:00
parent 1e29a170de
commit 6ef58f70c1
1 changed files with 36 additions and 49 deletions
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85
src/flow/flow.rs
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@ -46,7 +46,11 @@ pub fn compute_flow(
// TODO prune
println!("Max flow: {flow}");
let transfers = extract_transfers(source, sink, &flow, used_edges);
let transfers = if flow == U256::from(0) {
vec![]
} else {
extract_transfers(source, sink, &flow, used_edges)
};
println!("Num transfers: {}", transfers.len());
flow.to_string()
}
@ -106,74 +110,57 @@ fn extract_transfers(
while !account_balances.is_empty()
&& (account_balances.len() > 1 || *account_balances.iter().nth(0).unwrap().0 != *sink)
{
let next = extract_next_transfers(&mut used_edges, &mut account_balances);
assert!(!next.is_empty());
transfers.extend(next.into_iter());
println!(
"Finding next transfers. Number of non-zero-balance accounts: {}",
account_balances.len()
);
let edge = next_full_capacity_edge(&mut used_edges, &mut account_balances);
account_balances
.entry(edge.from)
.and_modify(|balance| *balance -= edge.capacity);
account_balances
.entry(edge.to)
.and_modify(|balance| *balance += edge.capacity);
account_balances.retain(|_account, balance| balance > &mut U256::from(0));
used_edges
.entry(Node::Node(edge.from))
.and_modify(|outgoing| {
outgoing.remove(&Node::TokenEdge(edge.from, edge.token));
});
transfers.push(edge);
}
transfers
}
/// Extract the next list of transfers until we get to a situation where
/// we cannot transfer the full balance and start over.
fn extract_next_transfers(
used_edges: &mut HashMap<Node, HashMap<Node, U256>>,
account_balances: &mut HashMap<Address, U256>,
) -> Vec<Edge> {
let mut transfers = Vec::new();
loop {
let first_edge = transfers.is_empty();
if let Some(edge) = next_nonzero_edge(used_edges, account_balances, first_edge) {
account_balances
.entry(edge.from)
.and_modify(|balance| *balance -= edge.capacity);
account_balances
.entry(edge.to)
.and_modify(|balance| *balance += edge.capacity);
account_balances.retain(|_account, balance| balance > &mut U256::from(0));
used_edges
.entry(Node::Node(edge.from))
.and_modify(|outgoing| {
outgoing.remove(&Node::TokenEdge(edge.from, edge.token));
});
transfers.push(edge);
} else {
return transfers;
}
}
}
fn next_nonzero_edge(
fn next_full_capacity_edge(
used_edges: &HashMap<Node, HashMap<Node, U256>>,
account_balances: &HashMap<Address, U256>,
first_edge: bool,
) -> Option<Edge> {
) -> Edge {
for (account, balance) in account_balances {
for (intermediate, _) in &used_edges[&Node::Node(*account)] {
println!("Account: {account} - balance: {balance}");
for (intermediate, _) in used_edges
.get(&Node::Node(*account))
.unwrap_or(&HashMap::default())
{
let (from, token) = node_as_token_edge(intermediate);
for (to_node, capacity) in &used_edges[intermediate] {
println!(" - used edge to {to_node} with capacity {capacity}");
let to = node_as_address(to_node);
if *capacity == U256::from(0) {
continue;
}
if *balance < *capacity {
// We do not have enough balance yet, there will be another transfer along this edge.
if first_edge {
continue;
} else {
return None;
}
} else {
return Some(Edge {
if *balance >= *capacity {
println!("Found an edge: {from} -> {to} [{token}] {capacity}");
return Edge {
from: *from,
to: *to,
token: *token,
capacity: *capacity,
});
};
}
}
}
}
None
panic!();
}