Rename Palette to FRAME (#4182)

* palette -> frame * PALETTE, Palette -> FRAME * Move folder pallete -> frame * Update docs/Structure.adoc Co-Authored-By: Benjamin Kampmann <ben.kampmann@googlemail.com> * Update docs/README.adoc Co-Authored-By: Benjamin Kampmann <ben.kampmann@googlemail.com> * Update README.adoc
2026-05-30 04:41:03 +00:00 · 2019-11-22 19:21:25 +01:00
parent 68351da29b
commit c9175b59ff
206 changed files with 485 additions and 483 deletions
@@ -0,0 +1,425 @@
+extern crate proc_macro;
+
+mod log;
+
+use log::log2;
+use proc_macro::TokenStream;
+use proc_macro2::{TokenStream as TokenStream2, Span};
+use proc_macro_crate::crate_name;
+use quote::{quote, ToTokens};
+use std::convert::TryInto;
+use syn::parse::{Parse, ParseStream};
+
+/// Accepts a number of expressions to create a instance of PiecewiseLinear which represents the
+/// NPoS curve (as detailed
+/// [here](http://research.web3.foundation/en/latest/polkadot/Token%20Economics/#inflation-model))
+/// for those parameters. Parameters are:
+/// - `min_inflation`: the minimal amount to be rewarded between validators, expressed as a fraction
+///   of total issuance. Known as `I_0` in the literature.
+///   Expressed in millionth, must be between 0 and 1_000_000.
+///
+/// - `max_inflation`: the maximum amount to be rewarded between validators, expressed as a fraction
+///   of total issuance. This is attained only when `ideal_stake` is achieved.
+///   Expressed in millionth, must be between min_inflation and 1_000_000.
+///
+/// - `ideal_stake`: the fraction of total issued tokens that should be actively staked behind
+///   validators. Known as `x_ideal` in the literature.
+///   Expressed in millionth, must be between 0_100_000 and 0_900_000.
+///
+/// - `falloff`: Known as `decay_rate` in the literature. A co-efficient dictating the strength of
+///   the global incentivisation to get the `ideal_stake`. A higher number results in less typical
+///   inflation at the cost of greater volatility for validators.
+///   Expressed in millionth, must be between 0 and 1_000_000.
+///
+/// - `max_piece_count`: The maximum number of pieces in the curve. A greater number uses more
+///   resources but results in higher accuracy.
+///   Must be between 2 and 1_000.
+///
+/// - `test_precision`: The maximum error allowed in the generated test.
+///   Expressed in millionth, must be between 0 and 1_000_000.
+///
+/// # Example
+///
+/// ```
+/// # fn main() {}
+/// use sr_primitives::curve::PiecewiseLinear;
+///
+/// pallet_staking_reward_curve::build! {
+/// 	const I_NPOS: PiecewiseLinear<'static> = curve!(
+/// 		min_inflation: 0_025_000,
+/// 		max_inflation: 0_100_000,
+/// 		ideal_stake: 0_500_000,
+/// 		falloff: 0_050_000,
+/// 		max_piece_count: 40,
+/// 		test_precision: 0_005_000,
+/// 	);
+/// }
+/// ```
+#[proc_macro]
+pub fn build(input: TokenStream) -> TokenStream {
+	let input = syn::parse_macro_input!(input as INposInput);
+
+	let points = compute_points(&input);
+
+	let declaration = generate_piecewise_linear(points);
+	let test_module = generate_test_module(&input);
+
+	let imports = match crate_name("sr-primitives") {
+		Ok(sr_primitives) => {
+			let ident = syn::Ident::new(&sr_primitives, Span::call_site());
+			quote!( extern crate #ident as _sr_primitives; )
+		},
+		Err(e) => syn::Error::new(Span::call_site(), &e).to_compile_error(),
+	};
+
+	let const_name = input.ident;
+	let const_type = input.typ;
+
+	quote!(
+		const #const_name: #const_type = {
+			#imports
+			#declaration
+		};
+		#test_module
+	).into()
+}
+
+const MILLION: u32 = 1_000_000;
+
+mod keyword {
+	syn::custom_keyword!(curve);
+	syn::custom_keyword!(min_inflation);
+	syn::custom_keyword!(max_inflation);
+	syn::custom_keyword!(ideal_stake);
+	syn::custom_keyword!(falloff);
+	syn::custom_keyword!(max_piece_count);
+	syn::custom_keyword!(test_precision);
+}
+
+struct INposInput {
+	ident: syn::Ident,
+	typ: syn::Type,
+	min_inflation: u32,
+	ideal_stake: u32,
+	max_inflation: u32,
+	falloff: u32,
+	max_piece_count: u32,
+	test_precision: u32,
+}
+
+struct Bounds {
+	min: u32,
+	min_strict: bool,
+	max: u32,
+	max_strict: bool,
+}
+
+impl Bounds {
+	fn check(&self, value: u32) -> bool {
+		let wrong = (self.min_strict && value <= self.min)
+			|| (!self.min_strict && value < self.min)
+			|| (self.max_strict && value >= self.max)
+			|| (!self.max_strict && value > self.max);
+
+		!wrong
+	}
+}
+
+impl core::fmt::Display for Bounds {
+	fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+		write!(
+			f,
+			"{}{:07}; {:07}{}",
+			if self.min_strict { "]" } else { "[" },
+			self.min,
+			self.max,
+			if self.max_strict { "[" } else { "]" },
+		)
+	}
+}
+
+fn parse_field<Token: Parse + Default + ToTokens>(input: ParseStream, bounds: Bounds)
+	-> syn::Result<u32>
+{
+	<Token>::parse(&input)?;
+	<syn::Token![:]>::parse(&input)?;
+	let value_lit = syn::LitInt::parse(&input)?;
+	let value: u32 = value_lit.base10_parse()?;
+	if !bounds.check(value) {
+		return Err(syn::Error::new(value_lit.span(), format!(
+			"Invalid {}: {},  must be in {}", Token::default().to_token_stream(), value, bounds,
+		)));
+	}
+
+	Ok(value)
+}
+
+impl Parse for INposInput {
+	fn parse(input: ParseStream) -> syn::Result<Self> {
+		let args_input;
+
+		<syn::Token![const]>::parse(&input)?;
+		let ident = <syn::Ident>::parse(&input)?;
+		<syn::Token![:]>::parse(&input)?;
+		let typ = <syn::Type>::parse(&input)?;
+		<syn::Token![=]>::parse(&input)?;
+		<keyword::curve>::parse(&input)?;
+		<syn::Token![!]>::parse(&input)?;
+		syn::parenthesized!(args_input in input);
+		<syn::Token![;]>::parse(&input)?;
+
+		if !input.is_empty() {
+			return Err(input.error("expected end of input stream, no token expected"));
+		}
+
+		let min_inflation = parse_field::<keyword::min_inflation>(&args_input, Bounds {
+			min: 0,
+			min_strict: true,
+			max: 1_000_000,
+			max_strict: false,
+		})?;
+		<syn::Token![,]>::parse(&args_input)?;
+		let max_inflation = parse_field::<keyword::max_inflation>(&args_input, Bounds {
+			min: min_inflation,
+			min_strict: true,
+			max: 1_000_000,
+			max_strict: false,
+		})?;
+		<syn::Token![,]>::parse(&args_input)?;
+		let ideal_stake = parse_field::<keyword::ideal_stake>(&args_input, Bounds {
+			min: 0_100_000,
+			min_strict: false,
+			max: 0_900_000,
+			max_strict: false,
+		})?;
+		<syn::Token![,]>::parse(&args_input)?;
+		let falloff = parse_field::<keyword::falloff>(&args_input, Bounds {
+			min: 0_010_000,
+			min_strict: false,
+			max: 1_000_000,
+			max_strict: false,
+		})?;
+		<syn::Token![,]>::parse(&args_input)?;
+		let max_piece_count = parse_field::<keyword::max_piece_count>(&args_input, Bounds {
+			min: 2,
+			min_strict: false,
+			max: 1_000,
+			max_strict: false,
+		})?;
+		<syn::Token![,]>::parse(&args_input)?;
+		let test_precision = parse_field::<keyword::test_precision>(&args_input, Bounds {
+			min: 0,
+			min_strict: false,
+			max: 1_000_000,
+			max_strict: false,
+		})?;
+		<Option<syn::Token![,]>>::parse(&args_input)?;
+
+		if !args_input.is_empty() {
+			return Err(args_input.error("expected end of input stream, no token expected"));
+		}
+
+		Ok(Self {
+			ident,
+			typ,
+			min_inflation,
+			ideal_stake,
+			max_inflation,
+			falloff,
+			max_piece_count,
+			test_precision,
+		})
+	}
+}
+
+struct INPoS {
+	i_0: u32,
+	i_ideal_times_x_ideal: u32,
+	i_ideal: u32,
+	x_ideal: u32,
+	d: u32,
+}
+
+impl INPoS {
+	fn from_input(input: &INposInput) -> Self {
+		INPoS {
+			i_0: input.min_inflation,
+			i_ideal: (input.max_inflation as u64 * MILLION as u64 / input.ideal_stake as u64)
+				.try_into().unwrap(),
+			i_ideal_times_x_ideal: input.max_inflation,
+			x_ideal: input.ideal_stake,
+			d: input.falloff,
+		}
+	}
+
+	fn compute_opposite_after_x_ideal(&self, y: u32) -> u32 {
+		if y == self.i_0 {
+			return u32::max_value();
+		}
+		let log = log2(self.i_ideal_times_x_ideal - self.i_0, y - self.i_0);
+
+		let term: u32 = ((self.d as u64 * log as u64) / 1_000_000).try_into().unwrap();
+
+		self.x_ideal + term
+	}
+}
+
+fn compute_points(input: &INposInput) -> Vec<(u32, u32)> {
+	let inpos = INPoS::from_input(input);
+
+	let mut points = vec![];
+	points.push((0, inpos.i_0));
+	points.push((inpos.x_ideal, inpos.i_ideal_times_x_ideal));
+
+	// For each point p: (next_p.0 - p.0) < segment_lenght && (next_p.1 - p.1) < segment_lenght.
+	// This ensures that the total number of segment doesn't overflow max_piece_count.
+	let max_length = (input.max_inflation - input.min_inflation + 1_000_000 - inpos.x_ideal)
+		/ (input.max_piece_count - 1);
+
+	let mut delta_y = max_length;
+	let mut y = input.max_inflation;
+
+	// The algorithm divide the curve in segment with vertical len and horizontal len less
+	// than `max_length`. This is not very accurate in case of very consequent steep.
+	while delta_y != 0 {
+		let next_y = y - delta_y;
+
+		if next_y <= input.min_inflation {
+			delta_y = delta_y.saturating_sub(1);
+			continue
+		}
+
+		let next_x = inpos.compute_opposite_after_x_ideal(next_y);
+
+		if (next_x - points.last().unwrap().0) > max_length {
+			delta_y = delta_y.saturating_sub(1);
+			continue
+		}
+
+		if next_x >= 1_000_000 {
+			let prev = points.last().unwrap();
+			// Compute the y corresponding to x=1_000_000 using the this point and the previous one.
+
+			let delta_y: u32 = (
+				(next_x - 1_000_000) as u64
+				* (prev.1 - next_y) as u64
+				/ (next_x - prev.0) as u64
+			).try_into().unwrap();
+
+			let y = next_y + delta_y;
+
+			points.push((1_000_000, y));
+			return points;
+		}
+		points.push((next_x, next_y));
+		y = next_y;
+	}
+
+	points.push((1_000_000, inpos.i_0));
+
+	points
+}
+
+fn generate_piecewise_linear(points: Vec<(u32, u32)>) -> TokenStream2 {
+	let mut points_tokens = quote!();
+
+	let max = points.iter()
+		.map(|&(_, x)| x)
+		.max()
+		.unwrap_or(0)
+		.checked_mul(1_000)
+		// clip at 1.0 for sanity only since it'll panic later if too high.
+		.unwrap_or(1_000_000_000);
+
+	for (x, y) in points {
+		let error = || panic!(format!(
+			"Generated reward curve approximation doesn't fit into [0, 1] -> [0, 1] \
+			because of point:
+			x = {:07} per million
+			y = {:07} per million",
+			x, y
+		));
+
+		let x_perbill = x.checked_mul(1_000).unwrap_or_else(error);
+		let y_perbill = y.checked_mul(1_000).unwrap_or_else(error);
+
+		points_tokens.extend(quote!(
+			(
+				_sr_primitives::Perbill::from_parts(#x_perbill),
+				_sr_primitives::Perbill::from_parts(#y_perbill),
+			),
+		));
+	}
+
+	quote!(
+		_sr_primitives::curve::PiecewiseLinear::<'static> {
+			points: & [ #points_tokens ],
+			maximum: _sr_primitives::Perbill::from_parts(#max),
+		}
+	)
+}
+
+fn generate_test_module(input: &INposInput) -> TokenStream2 {
+	let inpos = INPoS::from_input(input);
+
+	let ident = &input.ident;
+	let precision = input.test_precision;
+	let i_0 = inpos.i_0 as f64/ MILLION as f64;
+	let i_ideal_times_x_ideal = inpos.i_ideal_times_x_ideal as f64 / MILLION as f64;
+	let i_ideal = inpos.i_ideal as f64 / MILLION as f64;
+	let x_ideal = inpos.x_ideal as f64 / MILLION as f64;
+	let d = inpos.d as f64 / MILLION as f64;
+	let max_piece_count = input.max_piece_count;
+
+	quote!(
+		#[cfg(test)]
+		mod __pallet_staking_reward_curve_test_module {
+			fn i_npos(x: f64) -> f64 {
+				if x <= #x_ideal {
+					#i_0 + x * (#i_ideal - #i_0 / #x_ideal)
+				} else {
+					#i_0 + (#i_ideal_times_x_ideal - #i_0) * 2_f64.powf((#x_ideal - x) / #d)
+				}
+			}
+
+			const MILLION: u32 = 1_000_000;
+
+			#[test]
+			fn reward_curve_precision() {
+				for &base in [MILLION, u32::max_value()].into_iter() {
+					let number_of_check = 100_000.min(base);
+					for check_index in 0..=number_of_check {
+						let i = (check_index as u64 * base as u64 / number_of_check as u64) as u32;
+						let x = i as f64 / base as f64;
+						let float_res = (i_npos(x) * base as f64).round() as u32;
+						let int_res = super::#ident.calculate_for_fraction_times_denominator(i, base);
+						let err = (
+							(float_res.max(int_res) - float_res.min(int_res)) as u64
+							* MILLION as u64
+							/ float_res as u64
+						) as u32;
+						if err > #precision {
+							panic!(format!("\n\
+								Generated reward curve approximation differ from real one:\n\t\
+								for i = {} and base = {}, f(i/base) * base = {},\n\t\
+								but approximation = {},\n\t\
+								err = {:07} millionth,\n\t\
+								try increase the number of segment: {} or the test_error: {}.\n",
+								i, base, float_res, int_res, err, #max_piece_count, #precision
+							));
+						}
+					}
+				}
+			}
+
+			#[test]
+			fn reward_curve_piece_count() {
+				assert!(
+					super::#ident.points.len() as u32 - 1 <= #max_piece_count,
+					"Generated reward curve approximation is invalid: \
+					has more points than specified, please fill an issue."
+				);
+			}
+		}
+	).into()
+}
@@ -0,0 +1,70 @@
+use std::convert::TryInto;
+
+/// Return Per-million value.
+pub fn log2(p: u32, q: u32) -> u32 {
+	assert!(p >= q);
+	assert!(p <= u32::max_value()/2);
+
+	// This restriction should not be mandatory. But function is only tested and used for this.
+	assert!(p <= 1_000_000);
+	assert!(q <= 1_000_000);
+
+	if p == q {
+		return 0
+	}
+
+	let mut n = 0u32;
+	while !(p >= 2u32.pow(n)*q) || !(p < 2u32.pow(n+1)*q) {
+		n += 1;
+	}
+	assert!(p < 2u32.pow(n+1) * q);
+
+	let y_num: u32 = (p - 2u32.pow(n) * q).try_into().unwrap();
+	let y_den: u32 = (p + 2u32.pow(n) * q).try_into().unwrap();
+
+	let _2_div_ln_2 = 2_885_390u32;
+
+	let taylor_term = |k: u32| -> u32 {
+		if k == 0 {
+			(_2_div_ln_2 as u128 * (y_num as u128).pow(1) / (y_den as u128).pow(1))
+				.try_into().unwrap()
+		} else {
+			let mut res = _2_div_ln_2 as u128 * (y_num as u128).pow(3) / (y_den as u128).pow(3);
+			for _ in 1..k {
+				res = res * (y_num as u128).pow(2) / (y_den as u128).pow(2);
+			}
+			res /= 2 * k as u128 + 1;
+
+			res.try_into().unwrap()
+		}
+	};
+
+	let mut res = n * 1_000_000u32;
+	let mut k = 0;
+	loop {
+		let term = taylor_term(k);
+		if term == 0 {
+			break
+		}
+
+		res += term;
+		k += 1;
+	}
+
+	res
+}
+
+#[test]
+fn test_log() {
+	let div = 1_000;
+	for p in 0..=div {
+		for q in 1..=p {
+			let p: u32 = (1_000_000 as u64 * p as u64 / div as u64).try_into().unwrap();
+			let q: u32 = (1_000_000 as u64 * q as u64 / div as u64).try_into().unwrap();
+
+			let res = - (log2(p, q) as i64);
+			let expected = ((q as f64 / p as f64).log(2.0) * 1_000_000 as f64).round() as i64;
+			assert!((res - expected).abs() <= 6);
+		}
+	}
+}