Initial commit.
This commit is contained in:
commit
0e372df756
4 changed files with 343 additions and 0 deletions
1
.gitignore
vendored
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1
.gitignore
vendored
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@ -0,0 +1 @@
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/target
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175
Cargo.lock
generated
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175
Cargo.lock
generated
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@ -0,0 +1,175 @@
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# This file is automatically @generated by Cargo.
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# It is not intended for manual editing.
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version = 3
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[[package]]
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name = "aho-corasick"
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version = "1.1.3"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "8e60d3430d3a69478ad0993f19238d2df97c507009a52b3c10addcd7f6bcb916"
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dependencies = [
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"memchr",
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]
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[[package]]
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name = "bitexperimentation"
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version = "0.1.0"
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dependencies = [
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"quickcheck",
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"quickcheck_macros",
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]
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[[package]]
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name = "cfg-if"
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version = "1.0.0"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
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[[package]]
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name = "env_logger"
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version = "0.8.4"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "a19187fea3ac7e84da7dacf48de0c45d63c6a76f9490dae389aead16c243fce3"
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dependencies = [
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"log",
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"regex",
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]
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[[package]]
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name = "getrandom"
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version = "0.2.15"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "c4567c8db10ae91089c99af84c68c38da3ec2f087c3f82960bcdbf3656b6f4d7"
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dependencies = [
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"cfg-if",
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"libc",
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"wasi",
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]
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[[package]]
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name = "libc"
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version = "0.2.158"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "d8adc4bb1803a324070e64a98ae98f38934d91957a99cfb3a43dcbc01bc56439"
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[[package]]
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name = "log"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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[[package]]
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name = "memchr"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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[[package]]
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name = "proc-macro2"
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version = "1.0.86"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "5e719e8df665df0d1c8fbfd238015744736151d4445ec0836b8e628aae103b77"
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dependencies = [
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"unicode-ident",
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]
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[[package]]
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name = "quickcheck"
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version = "1.0.3"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "588f6378e4dd99458b60ec275b4477add41ce4fa9f64dcba6f15adccb19b50d6"
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dependencies = [
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"env_logger",
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"log",
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"rand",
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]
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[[package]]
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name = "quickcheck_macros"
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version = "1.0.0"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "b22a693222d716a9587786f37ac3f6b4faedb5b80c23914e7303ff5a1d8016e9"
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dependencies = [
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"proc-macro2",
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"quote",
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"syn",
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]
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[[package]]
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name = "quote"
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version = "1.0.37"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "b5b9d34b8991d19d98081b46eacdd8eb58c6f2b201139f7c5f643cc155a633af"
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dependencies = [
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"proc-macro2",
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]
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[[package]]
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name = "rand"
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version = "0.8.5"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "34af8d1a0e25924bc5b7c43c079c942339d8f0a8b57c39049bef581b46327404"
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dependencies = [
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"rand_core",
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]
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[[package]]
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name = "rand_core"
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version = "0.6.4"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "ec0be4795e2f6a28069bec0b5ff3e2ac9bafc99e6a9a7dc3547996c5c816922c"
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dependencies = [
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"getrandom",
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]
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[[package]]
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name = "regex"
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version = "1.10.6"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "4219d74c6b67a3654a9fbebc4b419e22126d13d2f3c4a07ee0cb61ff79a79619"
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dependencies = [
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"aho-corasick",
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"memchr",
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"regex-automata",
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"regex-syntax",
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]
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[[package]]
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name = "regex-automata"
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version = "0.4.7"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "38caf58cc5ef2fed281f89292ef23f6365465ed9a41b7a7754eb4e26496c92df"
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dependencies = [
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||||
"aho-corasick",
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"memchr",
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"regex-syntax",
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]
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[[package]]
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name = "regex-syntax"
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version = "0.8.4"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "7a66a03ae7c801facd77a29370b4faec201768915ac14a721ba36f20bc9c209b"
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[[package]]
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name = "syn"
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version = "1.0.109"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "72b64191b275b66ffe2469e8af2c1cfe3bafa67b529ead792a6d0160888b4237"
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dependencies = [
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||||
"proc-macro2",
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||||
"quote",
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||||
"unicode-ident",
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||||
]
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||||
[[package]]
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name = "unicode-ident"
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version = "1.0.13"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "e91b56cd4cadaeb79bbf1a5645f6b4f8dc5bde8834ad5894a8db35fda9efa1fe"
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||||
[[package]]
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name = "wasi"
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version = "0.11.0+wasi-snapshot-preview1"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "9c8d87e72b64a3b4db28d11ce29237c246188f4f51057d65a7eab63b7987e423"
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11
Cargo.toml
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11
Cargo.toml
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@ -0,0 +1,11 @@
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[package]
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name = "bitexperimentation"
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version = "0.1.0"
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edition = "2021"
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[dependencies]
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[dev-dependencies]
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quickcheck = "1"
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quickcheck_macros = "1"
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156
src/main.rs
Normal file
156
src/main.rs
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@ -0,0 +1,156 @@
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#[allow(non_snake_case)]
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fn L(k: u8) -> u64 {
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let mut s = 0;
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for i in 0..64u8.div_ceil(k) {
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s |= 1 << (i * k);
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}
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s
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}
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#[allow(non_snake_case)]
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fn H(k: u8) -> u64 {
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L(k) << (k - 1)
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}
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fn sideways_addition(x: u64) -> u64 {
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let s = x - ((x & 0xAAAAAAAAAAAAAAAA) >> 1);
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// 0xA = 0b1010
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let s = (s & 0x3333333333333333) + ((s >> 2) & 0x3333333333333333);
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// 0x3 = 0b0011
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let s = (s + (s >> 4)) & 0x0F0F0F0F0F0F0F0F;
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u64::wrapping_mul(s, L(8)) >> 56
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}
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fn less_equal_k_signed(x: u64, y: u64, k: u8) -> u64 {
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let s = (y | H(k)) - (x & !H(k));
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let s = s ^ x ^ y;
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let s = s | (x & !y);
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let s = s & !(!x & y);
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s & H(k)
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}
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fn less_equal_k_unsigned(x: u64, y: u64, k: u8) -> u64 {
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let s = (y | H(k)) - (x & !H(k));
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let s = s | x ^ y;
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let s = s ^ (x & !y);
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s & H(k)
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}
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fn grater_than_0_k_unsigned(x: u64, k: u8) -> u64 {
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(((x | H(k)) - L(k)) | x) & H(k)
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}
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fn select64(x: u64, r: u64) -> u64 {
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// Same as in sideways addition
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let s = x - ((x & 0xAAAAAAAAAAAAAAAA) >> 1);
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// 0xA = 0b1010
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let s = (s & 0x3333333333333333) + ((s >> 2) & 0x3333333333333333);
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// 0x3 = 0b0011
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let s = ((s + (s >> 4)) & 0x0F0F0F0F0F0F0F0F).wrapping_mul(L(8));
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// Select byte
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// b: byte index << 3
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let b =
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(less_equal_k_signed(s, r.wrapping_mul(L(8)), 8) >> 7).wrapping_mul(L(8)) >> 53 & (!0x7);
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if b == 64 {
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return 72;
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}
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// extract selected byte
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let l = r - (((s << 8) >> b) & 0xFF);
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// select index in byte
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let s = (grater_than_0_k_unsigned((x >> b & 0xFF).wrapping_mul(L(8)) & 0x8040201008040201, 8)
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>> 7)
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.wrapping_mul(L(8));
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b + ((less_equal_k_signed(s, l.wrapping_mul(L(8)), 8) >> 7).wrapping_mul(L(8)) >> 56)
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}
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fn trivial_select(data: u64, count: u8) -> u8 {
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let mut l = 0;
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let mut r = 63;
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while l < r {
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let m = (l + r) / 2;
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let shift = 64 - m - 1;
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let shifted = data << shift;
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let local_count = shifted.count_ones();
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// dbg!(l, r, m, shift, local_count, r);
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if local_count < count as u32 {
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l = m + 1;
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} else {
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r = m;
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}
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}
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l as u8
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}
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fn main() {
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dbg!(select64(3, 1));
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dbg!(trivial_select(3, 3));
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}
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#[cfg(test)]
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mod test {
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use quickcheck_macros::quickcheck;
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use crate::*;
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#[quickcheck]
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fn qc_test_sideways_addition(x: u64) -> bool {
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x.count_ones() as u64 == sideways_addition(x)
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}
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#[quickcheck]
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fn qc_less_equal_8_signed(x: u64, y: u64) -> bool {
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let s = less_equal_k_signed(x, y, 8).to_be_bytes();
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s.iter()
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.zip(x.to_be_bytes().iter().zip(y.to_be_bytes().iter()))
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.all(|(s, (&x, &y))| match s {
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0x00 => (x as i8) > (y as i8),
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0x80 => (x as i8) <= (y as i8),
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_ => false,
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})
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}
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#[quickcheck]
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fn qc_less_equal_k_unsigned(x: u64, y: u64) -> bool {
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let s = less_equal_k_unsigned(x, y, 8).to_be_bytes();
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s.iter()
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.zip(x.to_be_bytes().iter().zip(y.to_be_bytes().iter()))
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.all(|(s, (&x, &y))| match s {
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0x00 => x > y,
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0x80 => x <= y,
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_ => false,
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})
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}
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#[quickcheck]
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fn qc_grater_than_0_k_unsigned(x: u64) -> bool {
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let s = grater_than_0_k_unsigned(x, 8).to_be_bytes();
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s.iter().zip(x.to_be_bytes().iter()).all(|(a, b)| match a {
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0x00 => b == &0,
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0x80 => b > &0,
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_ => false,
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})
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}
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#[quickcheck]
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fn qc_select64(x: u64, r: u8) -> bool {
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let r = r.clamp(1, 64);
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let s = select64(x, r as u64);
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if x.count_ones() <= r as u32 {
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s == 72
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} else {
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trivial_select(x, r + 1) as u64 == s
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}
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||||
}
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||||
}
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