Add benches, examples to fork_choice

eth2/fork_choice/examples/example.rs

@@ -0,0 +1,40 @@
+use fork_choice::{test_utils::TestingForkChoiceBuilder, ForkChoice, OptimizedLMDGhost};
+use std::sync::Arc;
+use store::{MemoryStore, Store};
+use types::{BeaconBlock, ChainSpec, EthSpec, FoundationEthSpec, Hash256};
+
+fn main() {
+    let validator_count = 16;
+    let chain_length = 100;
+    let repetitions = 50;
+
+    let store = MemoryStore::open();
+    let builder: TestingForkChoiceBuilder<MemoryStore, FoundationEthSpec> =
+        TestingForkChoiceBuilder::new(validator_count, chain_length, Arc::new(store));
+
+    let fork_choosers: Vec<OptimizedLMDGhost<MemoryStore, FoundationEthSpec>> = (0..repetitions)
+        .into_iter()
+        .map(|_| builder.build())
+        .collect();
+
+    let spec = &FoundationEthSpec::spec();
+
+    println!("Running {} times...", repetitions);
+    for fc in fork_choosers {
+        do_thing(fc, &builder.chain, builder.genesis_root(), spec);
+    }
+}
+
+#[inline(never)]
+fn do_thing<F: ForkChoice<S>, S: Store>(
+    mut fc: F,
+    chain: &[(Hash256, BeaconBlock)],
+    genesis_root: Hash256,
+    spec: &ChainSpec,
+) {
+    for (root, block) in chain.iter().skip(1) {
+        fc.add_block(block, root, spec).unwrap();
+    }
+
+    let _head = fc.find_head(&genesis_root, spec).unwrap();
+}