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feat(kmd): reduce KMD AUR from 5% to 0.01% starting at nS7HardforkHeight #1841

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merged 2 commits into from
May 29, 2023
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feat(kmd): reduce KMD AUR from 5% to 0.01% starting at nS7HardforkHeight #1841

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6a0820a
reduce KMD AUR from 5% to 0.01% starting from nS7HardforkHeight
shamardy May 26, 2023
ea0d835
use constants for MINUTES_PER_YEAR, AUR_PER_MINUTE
shamardy May 29, 2023
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22 changes: 17 additions & 5 deletions mm2src/coins/utxo.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1574,7 +1574,6 @@ impl UtxoHDAccount {
}

/// Function calculating KMD interest
/// https://komodoplatform.atlassian.net/wiki/spaces/KPSD/pages/71729215/What+is+the+5+Komodo+Stake+Reward
/// https://github.com/KomodoPlatform/komodo/blob/master/src/komodo_interest.h
fn kmd_interest(
height: Option<u64>,
Expand All @@ -1584,6 +1583,12 @@ fn kmd_interest(
) -> Result<u64, KmdRewardsNotAccruedReason> {
const KOMODO_ENDOFERA: u64 = 7_777_777;
const LOCKTIME_THRESHOLD: u64 = 500_000_000;
// dPoW Season 7, Fri Jun 30 2023
const N_S7_HARDFORK_HEIGHT: u64 = 3_484_958;
// MINUTES_PER_YEAR = 365 * 24 * 60
const MINUTES_PER_YEAR: u64 = 525_600;
// Active user rewards per minute before N_S7_HARDFORK_HEIGHT
const AUR_PER_MINUTE: f64 = 0.05 / MINUTES_PER_YEAR as f64;

// value must be at least 10 KMD
if value < 1_000_000_000 {
Expand Down Expand Up @@ -1618,16 +1623,23 @@ fn kmd_interest(
}

// interest stop accruing after 1 year before block 1000000
if minutes > 365 * 24 * 60 {
minutes = 365 * 24 * 60
if minutes > MINUTES_PER_YEAR {
minutes = MINUTES_PER_YEAR
};
// interest stop accruing after 1 month past 1000000 block
if height >= 1_000_000 && minutes > 31 * 24 * 60 {
minutes = 31 * 24 * 60;
}
// next 2 lines ported as is from Komodo codebase
// Some of these lines are ported as is from Komodo codebase
minutes -= 59;
let accrued = (value / 10_512_000) * minutes;
let mut accrued = (value as f64 * AUR_PER_MINUTE) as u64 * minutes;
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Just curious to know, what's the purpose of introducing floating point arithmetic here, making a conversion from integer to float and vice versa, using drop_mutability! macros instead of simple:

    let accrued = if height >= N_S7_HARDFORK_HEIGHT {
        (value / 10_512_000) * minutes / 500
    } else {
        (value / 10_512_000) * minutes
    };

// KIP-0001 proposed a reduction of the AUR from 5% to 0.01%
// https://github.com/KomodoPlatform/kips/blob/main/kip-0001.mediawiki
// https://github.com/KomodoPlatform/komodo/pull/584
if height >= N_S7_HARDFORK_HEIGHT {
accrued /= 500;
};
drop_mutability!(accrued);

Ok(accrued)
}
Expand Down
15 changes: 15 additions & 0 deletions mm2src/coins/utxo/utxo_tests.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -348,6 +348,21 @@ fn test_kmd_interest_accrue_stop_at() {
assert_eq!(expected, actual);
}

#[test]
// Test case taken from this PR: https://github.com/KomodoPlatform/komodo/pull/584
fn test_kmd_interest_kip_0001_reduction() {
let height = Some(7777776);
let value = 64605500822;
let lock_time = 1663839248;
let current_time = 1663839248 + (31 * 24 * 60 - 1) * 60 + 3600;

// Starting from dPoW 7th season, according to KIP0001 AUR should be reduced from 5% to 0.01%, i.e. div by 500
let expected = value / 10512000 * (31 * 24 * 60 - 59) / 500;
println!("expected: {}", expected);
let actual = kmd_interest(height, value, lock_time, current_time).unwrap();
assert_eq!(expected, actual);
}

#[test]
fn test_sat_from_big_decimal() {
let amount = "0.000001".parse().unwrap();
Expand Down