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Merge pull request #271 from michaelsproul/log-int

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Fix log_int implementation, removing floats
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Age Manning 2019-03-03 00:13:55 +11:00 committed by GitHub
commit 684ef9f74c
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2 changed files with 15 additions and 15 deletions
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1
eth2/fork_choice/Cargo.toml
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@ -8,7 +8,6 @@ edition = "2018"
db = { path = "../../beacon_node/db" }
ssz = { path = "../utils/ssz" }
types = { path = "../types" }
fast-math = "0.1.1"
log = "0.4.6"
bit-vec = "0.5.0"

29
eth2/fork_choice/src/bitwise_lmd_ghost.rs
View File

@ -1,5 +1,5 @@
//! The optimised bitwise LMD-GHOST fork choice rule.
extern crate bit_vec;
extern crate fast_math;
use crate::{ForkChoice, ForkChoiceError};
use bit_vec::BitVec;
@ -7,7 +7,6 @@ use db::{
stores::{BeaconBlockStore, BeaconStateStore},
ClientDB,
};
use fast_math::log2_raw;
use log::{debug, trace};
use std::collections::HashMap;
use std::sync::Arc;
@ -19,22 +18,17 @@ use types::{
//TODO: Pruning - Children
//TODO: Handle Syncing
/// The optimised bitwise LMD-GHOST fork choice rule.
/// NOTE: This uses u32 to represent difference between block heights. Thus this is only
/// applicable for block height differences in the range of a u32.
/// This can potentially be parallelized in some parts.
// we use fast log2, a log2 lookup table is implemented in Vitaliks code, potentially do
// the comparison. Log2_raw takes 2ns according to the documentation.
// NOTE: This uses u32 to represent difference between block heights. Thus this is only
// applicable for block height differences in the range of a u32.
// This can potentially be parallelized in some parts.
/// Compute the base-2 logarithm of an integer, floored (rounded down)
#[inline]
fn log2_int(x: u32) -> u32 {
if x == 0 {
return 0;
}
assert!(
x <= std::f32::MAX as u32,
"Height too large for fast log in bitwise fork choice"
);
log2_raw(x as f32) as u32
31 - x.leading_zeros()
}
fn power_of_2_below(x: u32) -> u32 {
@ -469,7 +463,6 @@ mod tests {
#[test]
pub fn test_power_of_2_below() {
println!("{:?}", std::f32::MAX);
assert_eq!(power_of_2_below(4), 4);
assert_eq!(power_of_2_below(5), 4);
assert_eq!(power_of_2_below(7), 4);
@ -478,4 +471,12 @@ mod tests {
assert_eq!(power_of_2_below(33), 32);
assert_eq!(power_of_2_below(63), 32);
}
#[test]
pub fn test_power_of_2_below_large() {
let pow: u32 = 1 << 24;
for x in (pow - 20)..(pow + 20) {
assert!(power_of_2_below(x) <= x, "{}", x);
}
}
}