Generic Normalize impl for arithmetic and npos-elections (#6374)

* add normalize

* better api for normalize

* Some grumbles

* Update primitives/arithmetic/src/lib.rs

Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com>

* More great review grumbles

* Way better doc for everything.

* Some improvement

* Update primitives/arithmetic/src/lib.rs

Co-authored-by: Bernhard Schuster <bernhard@ahoi.io>

Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com>
Co-authored-by: Bernhard Schuster <bernhard@ahoi.io>

substrate/frame/staking/fuzzer/src/submit_solution.rs

@@ -44,7 +44,9 @@ enum Mode {
 }
 
 pub fn new_test_ext(iterations: u32) -> sp_io::TestExternalities {
-	let mut ext: sp_io::TestExternalities = frame_system::GenesisConfig::default().build_storage::<mock::Test>().map(Into::into)
+	let mut ext: sp_io::TestExternalities = frame_system::GenesisConfig::default()
+		.build_storage::<mock::Test>()
+		.map(Into::into)
 		.expect("Failed to create test externalities.");
 
 	let (offchain, offchain_state) = TestOffchainExt::new();
@@ -70,26 +72,29 @@ fn main() {
 	loop {
 		fuzz!(|data: (u32, u32, u32, u32, u32)| {
 			let (mut num_validators, mut num_nominators, mut edge_per_voter, mut to_elect, mode_u32) = data;
+			// always run with 5 iterations.
 			let mut ext = new_test_ext(5);
 			let mode: Mode = unsafe { std::mem::transmute(mode_u32) };
 			num_validators = to_range(num_validators, 50, 1000);
 			num_nominators = to_range(num_nominators, 50, 2000);
 			edge_per_voter = to_range(edge_per_voter, 1, 16);
 			to_elect = to_range(to_elect, 20, num_validators);
+
 			let do_reduce = true;
 
-			println!("+++ instance with params {} / {} / {} / {:?}({}) / {}",
+			println!("+++ instance with params {} / {} / {} / {} / {:?}({})",
 				num_nominators,
 				num_validators,
 				edge_per_voter,
+				to_elect,
 				mode,
 				mode_u32,
-				to_elect,
 			);
 
 			ext.execute_with(|| {
 				// initial setup
 				init_active_era();
+
 				assert_ok!(create_validators_with_nominators_for_era::<Test>(
 					num_validators,
 					num_nominators,
@@ -97,11 +102,11 @@ fn main() {
 					true,
 					None,
 				));
+
 				<EraElectionStatus<Test>>::put(ElectionStatus::Open(1));
 				assert!(<Staking<Test>>::create_stakers_snapshot().0);
-				let origin = RawOrigin::Signed(create_funded_user::<Test>("fuzzer", 0, 100));
 
-				println!("++ Chain setup done.");
+				let origin = RawOrigin::Signed(create_funded_user::<Test>("fuzzer", 0, 100));
 
 				// stuff to submit
 				let (winners, compact, score, size) = match mode {
@@ -141,8 +146,6 @@ fn main() {
 					}
 				};
 
-				println!("++ Submission ready. Score = {:?}", score);
-
 				// must have chosen correct number of winners.
 				assert_eq!(winners.len() as u32, <Staking<Test>>::validator_count());
 

substrate/frame/staking/src/offchain_election.rs

@@ -203,7 +203,8 @@ pub fn prepare_submission<T: Trait>(
 	}
 
 	// Convert back to ratio assignment. This takes less space.
-	let low_accuracy_assignment = sp_npos_elections::assignment_staked_to_ratio(staked);
+	let low_accuracy_assignment = sp_npos_elections::assignment_staked_to_ratio_normalized(staked)
+		.map_err(|e| OffchainElectionError::from(e))?;
 
 	// convert back to staked to compute the score in the receiver's accuracy. This can be done
 	// nicer, for now we do it as such since this code is not time-critical. This ensure that the

substrate/frame/staking/src/testing_utils.rs

@@ -201,11 +201,8 @@ pub fn get_weak_solution<T: Trait>(
 	};
 
 	// convert back to ratio assignment. This takes less space.
-	let low_accuracy_assignment: Vec<Assignment<T::AccountId, OffchainAccuracy>> =
-		staked_assignments
-			.into_iter()
-			.map(|sa| sa.into_assignment(true))
-			.collect();
+	let low_accuracy_assignment = assignment_staked_to_ratio_normalized(staked_assignments)
+		.expect("Failed to normalize");
 
 	// re-calculate score based on what the chain will decode.
 	let score = {