Correct approximate log-times-2048 tables for small values

The table generation didn't exactly match the lookup logic, causing
values below 2^6 to not always line up correctly.

diff --git a/lightning/src/routing/scoring.rs b/lightning/src/routing/scoring.rs
index 9c907c3f7fe4bd38d7526b9d10871769ea537d27..91349d845179b89a811cdec77d96512af8f0799f 100644 (file)
--- a/lightning/src/routing/scoring.rs
+++ b/lightning/src/routing/scoring.rs
@@ -1477,26 +1477,26 @@ mod approx {
                        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
                        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
                        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
-               [617, 617, 617, 617, 617, 617, 617, 617, 617, 617, 617, 617, 617, 617, 617, 617,
-                       617, 617, 617, 617, 617, 617, 617, 617, 617, 617, 617, 617, 617, 617, 617, 617,
-                       977, 977, 977, 977, 977, 977, 977, 977, 977, 977, 977, 977, 977, 977, 977, 977,
-                       977, 977, 977, 977, 977, 977, 977, 977, 977, 977, 977, 977, 977, 977, 977, 977],
-               [1233, 1233, 1233, 1233, 1233, 1233, 1233, 1233, 1233, 1233, 1233, 1233, 1233, 1233, 1233, 1233,
-                       1431, 1431, 1431, 1431, 1431, 1431, 1431, 1431, 1431, 1431, 1431, 1431, 1431, 1431, 1431, 1431,
-                       1594, 1594, 1594, 1594, 1594, 1594, 1594, 1594, 1594, 1594, 1594, 1594, 1594, 1594, 1594, 1594,
-                       1731, 1731, 1731, 1731, 1731, 1731, 1731, 1731, 1731, 1731, 1731, 1731, 1731, 1731, 1731, 1731],
-               [1850, 1850, 1850, 1850, 1850, 1850, 1850, 1850, 1954, 1954, 1954, 1954, 1954, 1954, 1954, 1954,
-                       2048, 2048, 2048, 2048, 2048, 2048, 2048, 2048, 2133, 2133, 2133, 2133, 2133, 2133, 2133, 2133,
-                       2210, 2210, 2210, 2210, 2210, 2210, 2210, 2210, 2281, 2281, 2281, 2281, 2281, 2281, 2281, 2281,
-                       2347, 2347, 2347, 2347, 2347, 2347, 2347, 2347, 2409, 2409, 2409, 2409, 2409, 2409, 2409, 2409],
-               [2466, 2466, 2466, 2466, 2520, 2520, 2520, 2520, 2571, 2571, 2571, 2571, 2619, 2619, 2619, 2619,
-                       2665, 2665, 2665, 2665, 2708, 2708, 2708, 2708, 2749, 2749, 2749, 2749, 2789, 2789, 2789, 2789,
-                       2827, 2827, 2827, 2827, 2863, 2863, 2863, 2863, 2898, 2898, 2898, 2898, 2931, 2931, 2931, 2931,
-                       2964, 2964, 2964, 2964, 2995, 2995, 2995, 2995, 3025, 3025, 3025, 3025, 3054, 3054, 3054, 3054],
-               [3083, 3083, 3110, 3110, 3136, 3136, 3162, 3162, 3187, 3187, 3212, 3212, 3235, 3235, 3259, 3259,
-                       3281, 3281, 3303, 3303, 3324, 3324, 3345, 3345, 3366, 3366, 3386, 3386, 3405, 3405, 3424, 3424,
-                       3443, 3443, 3462, 3462, 3479, 3479, 3497, 3497, 3514, 3514, 3531, 3531, 3548, 3548, 3564, 3564,
-                       3580, 3580, 3596, 3596, 3612, 3612, 3627, 3627, 3642, 3642, 3656, 3656, 3671, 3671, 3685, 3685],
+               [617, 617, 617, 977, 617, 977, 617, 977, 617, 977, 617, 977, 617, 977, 617, 977,
+                       617, 977, 617, 977, 617, 977, 617, 977, 617, 977, 617, 977, 617, 977, 617, 977,
+                       617, 977, 617, 977, 617, 977, 617, 977, 617, 977, 617, 977, 617, 977, 617, 977,
+                       617, 977, 617, 977, 617, 977, 617, 977, 617, 977, 617, 977, 617, 977, 617, 977],
+               [1233, 1233, 1233, 1233, 1233, 1431, 1594, 1731, 1233, 1431, 1594, 1731, 1233, 1431, 1594, 1731,
+                       1233, 1431, 1594, 1731, 1233, 1431, 1594, 1731, 1233, 1431, 1594, 1731, 1233, 1431, 1594, 1731,
+                       1233, 1431, 1594, 1731, 1233, 1431, 1594, 1731, 1233, 1431, 1594, 1731, 1233, 1431, 1594, 1731,
+                       1233, 1431, 1594, 1731, 1233, 1431, 1594, 1731, 1233, 1431, 1594, 1731, 1233, 1431, 1594, 1731],
+               [1850, 1850, 1850, 1850, 1850, 1850, 1850, 1850, 1850, 1954, 2048, 2133, 2210, 2281, 2347, 2409,
+                       1850, 1954, 2048, 2133, 2210, 2281, 2347, 2409, 1850, 1954, 2048, 2133, 2210, 2281, 2347, 2409,
+                       1850, 1954, 2048, 2133, 2210, 2281, 2347, 2409, 1850, 1954, 2048, 2133, 2210, 2281, 2347, 2409,
+                       1850, 1954, 2048, 2133, 2210, 2281, 2347, 2409, 1850, 1954, 2048, 2133, 2210, 2281, 2347, 2409],
+               [2466, 2466, 2466, 2466, 2466, 2466, 2466, 2466, 2466, 2466, 2466, 2466, 2466, 2466, 2466, 2466,
+                       2466, 2520, 2571, 2619, 2665, 2708, 2749, 2789, 2827, 2863, 2898, 2931, 2964, 2995, 3025, 3054,
+                       2466, 2520, 2571, 2619, 2665, 2708, 2749, 2789, 2827, 2863, 2898, 2931, 2964, 2995, 3025, 3054,
+                       2466, 2520, 2571, 2619, 2665, 2708, 2749, 2789, 2827, 2863, 2898, 2931, 2964, 2995, 3025, 3054],
+               [3083, 3083, 3083, 3083, 3083, 3083, 3083, 3083, 3083, 3083, 3083, 3083, 3083, 3083, 3083, 3083,
+                       3083, 3083, 3083, 3083, 3083, 3083, 3083, 3083, 3083, 3083, 3083, 3083, 3083, 3083, 3083, 3083,
+                       3083, 3110, 3136, 3162, 3187, 3212, 3235, 3259, 3281, 3303, 3324, 3345, 3366, 3386, 3405, 3424,
+                       3443, 3462, 3479, 3497, 3514, 3531, 3548, 3564, 3580, 3596, 3612, 3627, 3642, 3656, 3671, 3685],
                [3699, 3713, 3726, 3740, 3753, 3766, 3779, 3791, 3804, 3816, 3828, 3840, 3852, 3864, 3875, 3886,
                        3898, 3909, 3919, 3930, 3941, 3951, 3962, 3972, 3982, 3992, 4002, 4012, 4022, 4031, 4041, 4050,
                        4060, 4069, 4078, 4087, 4096, 4105, 4114, 4122, 4131, 4139, 4148, 4156, 4164, 4173, 4181, 4189,
@@ -1754,18 +1754,25 @@ mod approx {
                fn prints_negative_log10_times_2048_lookup_table() {
                        for msb in 0..BITS {
                                for i in 0..LOWER_BITS_BOUND {
-                                       let x = ((LOWER_BITS_BOUND + i) << (HIGHEST_BIT - LOWER_BITS)) >> (HIGHEST_BIT - msb);
-                                       let log10_times_2048 = ((x as f64).log10() * 2048.0).round() as u16;
-                                       assert_eq!(log10_times_2048, LOG10_TIMES_2048[msb as usize][i as usize]);
+                                       let mut x = 1 << msb;
+                                       if msb >= LOWER_BITS || i >= (1 << msb) {
+                                               x |= i << msb.saturating_sub(LOWER_BITS);
+                                       }
+                                       x <<= 63 - msb;
+                                       x >>= 63 - msb;
+                                       if x == 0 { x = 1; }
+                                       let calc_log10_times_2048 = ((x as f64).log10() * 2048.0).round() as u16;
+                                       assert_eq!(calc_log10_times_2048, log10_times_2048(x));
+                                       assert_eq!(calc_log10_times_2048, LOG10_TIMES_2048[msb as usize][i as usize]);
 
                                        if i % LOWER_BITS_BOUND == 0 {
-                                               print!("\t\t[{}, ", log10_times_2048);
+                                               print!("\t\t[{}, ", calc_log10_times_2048);
                                        } else if i % LOWER_BITS_BOUND == LOWER_BITS_BOUND - 1 {
-                                               println!("{}],", log10_times_2048);
+                                               println!("{}],", calc_log10_times_2048);
                                        } else if i % (LOWER_BITS_BOUND/4) == LOWER_BITS_BOUND/4 - 1 {
-                                               print!("{},\n\t\t\t", log10_times_2048);
+                                               print!("{},\n\t\t\t", calc_log10_times_2048);
                                        } else {
-                                               print!("{}, ", log10_times_2048);
+                                               print!("{}, ", calc_log10_times_2048);
                                        }
                                }
                        }