sfbinpack 0.6.2

Library to read Stockfish Binpacks
Documentation 
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

#[cfg(all(target_arch = "x86_64", any(target_feature = "bmi2", feature = "bmi2")))]
use std::arch::x86_64::_pdep_u64;

#[cfg(all(target_arch = "x86_64", any(target_feature = "bmi2", feature = "bmi2")))]
#[target_feature(enable = "bmi2")]
unsafe fn nth_set_bit_index_bmi2(v: u64, n: u64) -> u32 {
    _pdep_u64(1u64 << n, v).trailing_zeros() as u32
}

const fn nth_set_bit_index_naive(mut value: u64, n: usize) -> u8 {
    let mut count = 0;
    while count < n {
        if value == 0 {
            break;
        }
        value &= value - 1;
        count += 1;
    }
    value.trailing_zeros() as u8
}

const fn create_lookup_table() -> [[u8; 8]; 256] {
    let mut table = [[0u8; 8]; 256];
    let mut i = 0;
    while i < 256 {
        let mut j = 0;
        while j < 8 {
            table[i][j] = nth_set_bit_index_naive(i as u64, j);
            j += 1;
        }
        i += 1;
    }
    table
}

const NTH_SET_BIT_INDEX: [[u8; 8]; 256] = create_lookup_table();

#[allow(unreachable_code)]
#[inline(always)]
pub fn nth_set_bit_index(v: u64, n: u64) -> u32 {
    #[cfg(all(target_arch = "x86_64", any(target_feature = "bmi2", feature = "bmi2")))]
    unsafe {
        return nth_set_bit_index_bmi2(v, n);
    }

    let mut value = v;
    let mut count = n;

    let mut shift: u64 = 0;
    let p = (value & 0xFFFFFFFF).count_ones() as u64;
    let pmask = ((p > count) as u64).wrapping_sub(1);
    value >>= 32 & pmask;
    shift += 32 & pmask;
    count -= p & pmask;

    let p = (value & 0xFFFF).count_ones() as u64;
    let pmask = ((p > count) as u64).wrapping_sub(1);
    value >>= 16 & pmask;
    shift += 16 & pmask;
    count -= p & pmask;

    let p = (value & 0xFF).count_ones() as u64;
    let pmask = ((p > count) as u64).wrapping_sub(1);
    value >>= 8 & pmask;
    shift += 8 & pmask;
    count -= p & pmask;

    (NTH_SET_BIT_INDEX[(value & 0xFF) as usize][count as usize] as u64 + shift) as u32
}

#[inline(always)]
pub fn unsigned_to_signed(r: u16) -> i16 {
    let mut v = r.rotate_right(1);
    if v & 0x8000 != 0 {
        v ^= 0x7FFF;
    }
    v as i16
}

#[inline]
pub fn signed_to_unsigned(a: i16) -> u16 {
    let mut r = i16::cast_unsigned(a);
    if r & 0x8000 != 0 {
        r ^= 0x7FFF;
    }
    r.rotate_left(1)
}

#[inline(always)]
pub const fn used_bits_safe(n: u64) -> usize {
    if n == 0 {
        0
    } else {
        (64 - (n - 1).leading_zeros()) as usize
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_nth_set_bit_index() {
        let test_value = 0b10110110u64;
        assert_eq!(nth_set_bit_index(test_value, 0), 1);
        assert_eq!(nth_set_bit_index(test_value, 1), 2);
        assert_eq!(nth_set_bit_index(test_value, 2), 4);
        assert_eq!(nth_set_bit_index(test_value, 3), 5);
        assert_eq!(nth_set_bit_index(test_value, 4), 7);
    }

    #[test]
    fn test_unsigned_to_signed() {
        assert_eq!(unsigned_to_signed(65409), -32705);
    }

    #[test]
    fn test_unsigned_to_signed_2() {
        assert_eq!(unsigned_to_signed(24), 12);
    }

    #[test]
    fn test_unsigned_to_signed_zero() {
        assert_eq!(unsigned_to_signed(0), 0);
    }

    #[test]
    fn test_unsigned_to_signed_one() {
        assert_eq!(unsigned_to_signed(1), -1);
    }

    #[test]
    fn test_unsigned_to_signed_two() {
        assert_eq!(unsigned_to_signed(2), 1);
    }

    #[test]
    fn test_unsigned_to_signed_three() {
        assert_eq!(unsigned_to_signed(3), -2);
    }

    #[test]
    fn test_used_bits_safe() {
        assert_eq!(used_bits_safe(0), 0);
        assert_eq!(used_bits_safe(1), 0);
        assert_eq!(used_bits_safe(12), 4);

        assert_eq!(used_bits_safe(2), 1);
        assert_eq!(used_bits_safe(4), 2);
        assert_eq!(used_bits_safe(8), 3);
        assert_eq!(used_bits_safe(1024), 10);

        assert_eq!(used_bits_safe(3), 2);
        assert_eq!(used_bits_safe(7), 3);
        assert_eq!(used_bits_safe(255), 8);

        assert_eq!(used_bits_safe(10), 4);
        assert_eq!(used_bits_safe(100), 7);
        assert_eq!(used_bits_safe(12345), 14);

        assert_eq!(used_bits_safe(u64::MAX), 64);
    }
}