1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400
//! Block and Miner subsidies, halvings and target spacing modifiers. - [§7.8][7.8]
//!
//! [7.8]: https://zips.z.cash/protocol/protocol.pdf#subsidies
use std::collections::HashSet;
use zebra_chain::{
amount::{Amount, Error, NonNegative},
block::{Height, HeightDiff},
parameters::{Network, NetworkUpgrade::*},
transaction::Transaction,
};
use crate::{funding_stream_values, parameters::subsidy::*};
/// The divisor used for halvings.
///
/// `1 << Halving(height)`, as described in [protocol specification §7.8][7.8]
///
/// [7.8]: https://zips.z.cash/protocol/protocol.pdf#subsidies
///
/// Returns `None` if the divisor would overflow a `u64`.
pub fn halving_divisor(height: Height, network: &Network) -> Option<u64> {
let blossom_height = Blossom
.activation_height(network)
.expect("blossom activation height should be available");
// TODO: Add this as a field on `testnet::Parameters` instead of checking `disable_pow()`, this is 0 for Regtest in zcashd,
// see <https://github.com/zcash/zcash/blob/master/src/chainparams.cpp#L640>
let slow_start_shift = if network.disable_pow() {
Height(0)
} else {
SLOW_START_SHIFT
};
if height < slow_start_shift {
unreachable!(
"unsupported block height {height:?}: checkpoints should handle blocks below {slow_start_shift:?}",
)
} else if height < blossom_height {
let pre_blossom_height = height - slow_start_shift;
let halving_shift = pre_blossom_height / PRE_BLOSSOM_HALVING_INTERVAL;
let halving_div = 1u64
.checked_shl(
halving_shift
.try_into()
.expect("already checked for negatives"),
)
.expect("pre-blossom heights produce small shifts");
Some(halving_div)
} else {
let pre_blossom_height = blossom_height - slow_start_shift;
let scaled_pre_blossom_height =
pre_blossom_height * HeightDiff::from(BLOSSOM_POW_TARGET_SPACING_RATIO);
let post_blossom_height = height - blossom_height;
let halving_shift =
(scaled_pre_blossom_height + post_blossom_height) / POST_BLOSSOM_HALVING_INTERVAL;
// Some far-future shifts can be more than 63 bits
1u64.checked_shl(
halving_shift
.try_into()
.expect("already checked for negatives"),
)
}
}
/// `BlockSubsidy(height)` as described in [protocol specification §7.8][7.8]
///
/// [7.8]: https://zips.z.cash/protocol/protocol.pdf#subsidies
pub fn block_subsidy(height: Height, network: &Network) -> Result<Amount<NonNegative>, Error> {
let blossom_height = Blossom
.activation_height(network)
.expect("blossom activation height should be available");
// If the halving divisor is larger than u64::MAX, the block subsidy is zero,
// because amounts fit in an i64.
//
// Note: bitcoind incorrectly wraps here, which restarts large block rewards.
let Some(halving_div) = halving_divisor(height, network) else {
return Ok(Amount::zero());
};
// TODO: Add this as a field on `testnet::Parameters` instead of checking `disable_pow()`, this is 0 for Regtest in zcashd,
// see <https://github.com/zcash/zcash/blob/master/src/chainparams.cpp#L640>
if height < SLOW_START_INTERVAL && !network.disable_pow() {
unreachable!(
"unsupported block height {height:?}: callers should handle blocks below {SLOW_START_INTERVAL:?}",
)
} else if height < blossom_height {
// this calculation is exact, because the halving divisor is 1 here
Amount::try_from(MAX_BLOCK_SUBSIDY / halving_div)
} else {
let scaled_max_block_subsidy =
MAX_BLOCK_SUBSIDY / u64::from(BLOSSOM_POW_TARGET_SPACING_RATIO);
// in future halvings, this calculation might not be exact
// Amount division is implemented using integer division,
// which truncates (rounds down) the result, as specified
Amount::try_from(scaled_max_block_subsidy / halving_div)
}
}
/// `MinerSubsidy(height)` as described in [protocol specification §7.8][7.8]
///
/// [7.8]: https://zips.z.cash/protocol/protocol.pdf#subsidies
pub fn miner_subsidy(height: Height, network: &Network) -> Result<Amount<NonNegative>, Error> {
let total_funding_stream_amount: Result<Amount<NonNegative>, _> =
funding_stream_values(height, network)?.values().sum();
block_subsidy(height, network)? - total_funding_stream_amount?
}
/// Returns all output amounts in `Transaction`.
pub fn output_amounts(transaction: &Transaction) -> HashSet<Amount<NonNegative>> {
transaction
.outputs()
.iter()
.map(|o| &o.value)
.cloned()
.collect()
}
#[cfg(test)]
mod test {
use super::*;
use color_eyre::Report;
#[test]
fn halving_test() -> Result<(), Report> {
let _init_guard = zebra_test::init();
for network in Network::iter() {
halving_for_network(&network)?;
}
Ok(())
}
fn halving_for_network(network: &Network) -> Result<(), Report> {
let blossom_height = Blossom.activation_height(network).unwrap();
let first_halving_height = network.height_for_first_halving();
assert_eq!(
1,
halving_divisor((SLOW_START_INTERVAL + 1).unwrap(), network).unwrap()
);
assert_eq!(
1,
halving_divisor((blossom_height - 1).unwrap(), network).unwrap()
);
assert_eq!(1, halving_divisor(blossom_height, network).unwrap());
assert_eq!(
1,
halving_divisor((first_halving_height - 1).unwrap(), network).unwrap()
);
assert_eq!(2, halving_divisor(first_halving_height, network).unwrap());
assert_eq!(
2,
halving_divisor((first_halving_height + 1).unwrap(), network).unwrap()
);
assert_eq!(
4,
halving_divisor(
(first_halving_height + POST_BLOSSOM_HALVING_INTERVAL).unwrap(),
network
)
.unwrap()
);
assert_eq!(
8,
halving_divisor(
(first_halving_height + (POST_BLOSSOM_HALVING_INTERVAL * 2)).unwrap(),
network
)
.unwrap()
);
assert_eq!(
1024,
halving_divisor(
(first_halving_height + (POST_BLOSSOM_HALVING_INTERVAL * 9)).unwrap(),
network
)
.unwrap()
);
assert_eq!(
1024 * 1024,
halving_divisor(
(first_halving_height + (POST_BLOSSOM_HALVING_INTERVAL * 19)).unwrap(),
network
)
.unwrap()
);
assert_eq!(
1024 * 1024 * 1024,
halving_divisor(
(first_halving_height + (POST_BLOSSOM_HALVING_INTERVAL * 29)).unwrap(),
network
)
.unwrap()
);
assert_eq!(
1024 * 1024 * 1024 * 1024,
halving_divisor(
(first_halving_height + (POST_BLOSSOM_HALVING_INTERVAL * 39)).unwrap(),
network
)
.unwrap()
);
// The largest possible integer divisor
assert_eq!(
(i64::MAX as u64 + 1),
halving_divisor(
(first_halving_height + (POST_BLOSSOM_HALVING_INTERVAL * 62)).unwrap(),
network
)
.unwrap(),
);
// Very large divisors which should also result in zero amounts
assert_eq!(
None,
halving_divisor(
(first_halving_height + (POST_BLOSSOM_HALVING_INTERVAL * 63)).unwrap(),
network,
),
);
assert_eq!(
None,
halving_divisor(
(first_halving_height + (POST_BLOSSOM_HALVING_INTERVAL * 64)).unwrap(),
network,
),
);
assert_eq!(
None,
halving_divisor(Height(Height::MAX_AS_U32 / 4), network),
);
assert_eq!(
None,
halving_divisor(Height(Height::MAX_AS_U32 / 2), network),
);
assert_eq!(None, halving_divisor(Height::MAX, network));
Ok(())
}
#[test]
fn block_subsidy_test() -> Result<(), Report> {
let _init_guard = zebra_test::init();
for network in Network::iter() {
block_subsidy_for_network(&network)?;
}
Ok(())
}
fn block_subsidy_for_network(network: &Network) -> Result<(), Report> {
let blossom_height = Blossom.activation_height(network).unwrap();
let first_halving_height = network.height_for_first_halving();
// After slow-start mining and before Blossom the block subsidy is 12.5 ZEC
// https://z.cash/support/faq/#what-is-slow-start-mining
assert_eq!(
Amount::try_from(1_250_000_000),
block_subsidy((SLOW_START_INTERVAL + 1).unwrap(), network)
);
assert_eq!(
Amount::try_from(1_250_000_000),
block_subsidy((blossom_height - 1).unwrap(), network)
);
// After Blossom the block subsidy is reduced to 6.25 ZEC without halving
// https://z.cash/upgrade/blossom/
assert_eq!(
Amount::try_from(625_000_000),
block_subsidy(blossom_height, network)
);
// After the 1st halving, the block subsidy is reduced to 3.125 ZEC
// https://z.cash/upgrade/canopy/
assert_eq!(
Amount::try_from(312_500_000),
block_subsidy(first_halving_height, network)
);
// After the 2nd halving, the block subsidy is reduced to 1.5625 ZEC
// See "7.8 Calculation of Block Subsidy and Founders' Reward"
assert_eq!(
Amount::try_from(156_250_000),
block_subsidy(
(first_halving_height + POST_BLOSSOM_HALVING_INTERVAL).unwrap(),
network
)
);
// After the 7th halving, the block subsidy is reduced to 0.04882812 ZEC
// Check that the block subsidy rounds down correctly, and there are no errors
assert_eq!(
Amount::try_from(4_882_812),
block_subsidy(
(first_halving_height + (POST_BLOSSOM_HALVING_INTERVAL * 6)).unwrap(),
network
)
);
// After the 29th halving, the block subsidy is 1 zatoshi
// Check that the block subsidy is calculated correctly at the limit
assert_eq!(
Amount::try_from(1),
block_subsidy(
(first_halving_height + (POST_BLOSSOM_HALVING_INTERVAL * 28)).unwrap(),
network
)
);
// After the 30th halving, there is no block subsidy
// Check that there are no errors
assert_eq!(
Amount::try_from(0),
block_subsidy(
(first_halving_height + (POST_BLOSSOM_HALVING_INTERVAL * 29)).unwrap(),
network
)
);
assert_eq!(
Amount::try_from(0),
block_subsidy(
(first_halving_height + (POST_BLOSSOM_HALVING_INTERVAL * 39)).unwrap(),
network
)
);
assert_eq!(
Amount::try_from(0),
block_subsidy(
(first_halving_height + (POST_BLOSSOM_HALVING_INTERVAL * 49)).unwrap(),
network
)
);
assert_eq!(
Amount::try_from(0),
block_subsidy(
(first_halving_height + (POST_BLOSSOM_HALVING_INTERVAL * 59)).unwrap(),
network
)
);
// The largest possible integer divisor
assert_eq!(
Amount::try_from(0),
block_subsidy(
(first_halving_height + (POST_BLOSSOM_HALVING_INTERVAL * 62)).unwrap(),
network
)
);
// Other large divisors which should also result in zero
assert_eq!(
Amount::try_from(0),
block_subsidy(
(first_halving_height + (POST_BLOSSOM_HALVING_INTERVAL * 63)).unwrap(),
network
)
);
assert_eq!(
Amount::try_from(0),
block_subsidy(
(first_halving_height + (POST_BLOSSOM_HALVING_INTERVAL * 64)).unwrap(),
network
)
);
assert_eq!(
Amount::try_from(0),
block_subsidy(Height(Height::MAX_AS_U32 / 4), network)
);
assert_eq!(
Amount::try_from(0),
block_subsidy(Height(Height::MAX_AS_U32 / 2), network)
);
assert_eq!(Amount::try_from(0), block_subsidy(Height::MAX, network));
Ok(())
}
}