Multi-limb arithmetic for runtime (#3743)

* First working version of all operations.

* New and improved version of everything.

* Minor cleanup.

* Fix build

* Finalize nignum

* Some final works on refactors and tests.

* fix build

* Some review comments

* Bench, better try into and nits

* mutify the API

* rename to big_uint

* unmutify.

* Remove resize

* Apply suggestions from code review

* Update core/sr-primitives/src/sr_arithmetic.rs

Co-Authored-By: thiolliere <gui.thiolliere@gmail.com>

* BEtter proof

* Fix panic doc.

* Bump.

substrate/core/phragmen/src/lib.rs

@@ -34,8 +34,8 @@
 #![cfg_attr(not(feature = "std"), no_std)]
 
 use rstd::{prelude::*, collections::btree_map::BTreeMap};
-use sr_primitives::{helpers_128bit::multiply_by_rational_best_effort, Perbill, Rational128};
-use sr_primitives::traits::{Zero, Convert, Member, SimpleArithmetic, Saturating};
+use sr_primitives::{helpers_128bit::multiply_by_rational, Perbill, Rational128};
+use sr_primitives::traits::{Zero, Convert, Member, SimpleArithmetic, Saturating, Bounded};
 
 mod mock;
 mod tests;
@@ -253,11 +253,11 @@ pub fn elect<AccountId, Balance, FS, C>(
 			for e in &n.edges {
 				let c = &mut candidates[e.candidate_index];
 				if !c.elected && !c.approval_stake.is_zero() {
-					let temp_n = multiply_by_rational_best_effort(
+					let temp_n = multiply_by_rational(
 						n.load.n(),
 						n.budget,
 						c.approval_stake,
-					);
+					).unwrap_or(Bounded::max_value());
 					let temp_d = n.load.d();
 					let temp = Rational128::from(temp_n, temp_d);
 					c.score = c.score.lazy_saturating_add(temp);
@@ -303,11 +303,11 @@ pub fn elect<AccountId, Balance, FS, C>(
 							if e.load.d() == n.load.d() {
 								// return e.load / n.load.
 								let desired_scale: u128 = Perbill::accuracy().into();
-								multiply_by_rational_best_effort(
+								multiply_by_rational(
 									desired_scale,
 									e.load.n(),
 									n.load.n(),
-								)
+								).unwrap_or(Bounded::max_value())
 							} else {
 								// defensive only. Both edge and nominator loads are built from
 								// scores, hence MUST have the same denominator.

substrate/core/sr-primitives/Cargo.toml

@@ -26,6 +26,7 @@ rand = "0.7.2"
 substrate-offchain = { path = "../offchain" }
 
 [features]
+bench = []
 default = ["std"]
 std = [
 	"num-traits/std",

substrate/core/sr-primitives/src/lib.rs

@@ -19,6 +19,10 @@
 #![warn(missing_docs)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
+// to allow benchmarking
+#![cfg_attr(feature = "bench", feature(test))]
+#[cfg(feature = "bench")] extern crate test;
+
 #[doc(hidden)]
 pub use codec;
 #[cfg(feature = "std")]
@@ -59,13 +63,15 @@ pub use generic::{DigestItem, Digest};
 pub use primitives::{TypeId, crypto::{key_types, KeyTypeId, CryptoType}};
 pub use app_crypto::RuntimeAppPublic;
 
-/// Re-export arithmetic stuff.
+/// Re-export top-level arithmetic stuff.
 pub use sr_arithmetic::{
 	Perquintill, Perbill, Permill, Percent,
 	Rational128, Fixed64
 };
-/// Re-export 128 bit helpers from sr_arithmetic
+/// Re-export 128 bit helpers.
 pub use sr_arithmetic::helpers_128bit;
+/// Re-export big_uint stiff.
+pub use sr_arithmetic::biguint;
 
 #[cfg(feature = "std")]
 pub use externalities::set_and_run_with_externalities;

substrate/node/runtime/src/lib.rs

@@ -84,8 +84,8 @@ pub const VERSION: RuntimeVersion = RuntimeVersion {
 	// and set impl_version to equal spec_version. If only runtime
 	// implementation changes and behavior does not, then leave spec_version as
 	// is and increment impl_version.
-	spec_version: 173,
-	impl_version: 173,
+	spec_version: 174,
+	impl_version: 174,
 	apis: RUNTIME_API_VERSIONS,
 };