Compute transfers.

This commit is contained in:
chriseth 2022-09-11 17:44:15 +02:00
parent fbe6183e57
commit 0191fb463a
3 changed files with 104 additions and 16 deletions

View file

@ -1,5 +1,5 @@
use crate::flow::adjacencies::Adjacencies; use crate::flow::adjacencies::Adjacencies;
use crate::flow::Node; use crate::flow::{node_as_address, node_as_token_edge, Node};
use crate::types::{Address, Edge, U256}; use crate::types::{Address, Edge, U256};
use std::cmp::min; use std::cmp::min;
use std::collections::HashMap; use std::collections::HashMap;
@ -43,6 +43,8 @@ pub fn compute_flow(
} }
} }
println!("Max flow: {flow}"); println!("Max flow: {flow}");
let transfers = extract_transfers(source, sink, &flow, used_edges);
println!("Num transfers: {}", transfers.len());
flow.to_string() flow.to_string()
} }
@ -87,3 +89,88 @@ fn trace(parent: HashMap<Node, Node>, source: &Node, sink: &Node) -> Vec<Node> {
} }
t t
} }
fn extract_transfers(
source: &Address,
sink: &Address,
amount: &U256,
mut used_edges: HashMap<Node, HashMap<Node, U256>>,
) -> Vec<Edge> {
let mut transfers: Vec<Edge> = Vec::new();
let mut account_balances: HashMap<Address, U256> = HashMap::new();
account_balances.insert(*source, amount.clone());
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());
}
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(
used_edges: &HashMap<Node, HashMap<Node, U256>>,
account_balances: &HashMap<Address, U256>,
first_edge: bool,
) -> Option<Edge> {
for (account, balance) in account_balances {
for (intermediate, _) in &used_edges[&Node::Node(*account)] {
let (from, token) = node_as_token_edge(intermediate);
for (to_node, capacity) in &used_edges[intermediate] {
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 {
from: *from,
to: *to,
token: *token,
capacity: *capacity,
});
}
}
}
}
None
}

View file

@ -10,6 +10,22 @@ pub enum Node {
TokenEdge(Address, Address), TokenEdge(Address, Address),
} }
pub fn node_as_address(node: &Node) -> &Address {
if let Node::Node(address) = node {
address
} else {
panic!()
}
}
pub fn node_as_token_edge(node: &Node) -> (&Address, &Address) {
if let Node::TokenEdge(from, token) = node {
(from, token)
} else {
panic!()
}
}
impl Display for Node { impl Display for Node {
fn fmt(&self, f: &mut Formatter) -> std::fmt::Result { fn fmt(&self, f: &mut Formatter) -> std::fmt::Result {
match self { match self {

View file

@ -83,21 +83,6 @@ impl Server {
} }
fn read_request(socket: &mut TcpStream) -> Result<JsonRpcRequest, Box<dyn Error>> { fn read_request(socket: &mut TcpStream) -> Result<JsonRpcRequest, Box<dyn Error>> {
// let mut buf_reader = BufReader::new(&mut socket);
// let http_request: Vec<_> = buf_reader
// .by_ref()
// .lines()
// .map(|result| result.unwrap())
// .take_while(|line| !line.is_empty())
// .collect();
// println!("{http_request:?}");
// let mut buf = [0; 74];
// buf_reader.read_exact(&mut buf)?;
// println!("payload: {buf:?}");
// let response = "HTTP/1.1 200 OK\r\n\r\n";
// socket.write_all(response.as_bytes()).unwrap();
let payload = read_payload(socket)?; let payload = read_payload(socket)?;
let mut request = json::parse(&String::from_utf8(payload)?)?; let mut request = json::parse(&String::from_utf8(payload)?)?;
println!("Request: {request}"); println!("Request: {request}");