Eval/the great refactor (#275)

* Use bytemuck to cast between weights struct and array

* Add EvalTrace to eval struct conditionally

* Add default trait for EvalTrace

because there's no generic default impl for arrays, as of yet

* Copy over all of the eval methods onto the eval struct

* Pass in explicit eval trace parameter

* Remove old eval implementation on Board

* Make eval terms standalone functions

Makes it easier to call from anywhere, without having to bootstrap a
full Eval struct

* Add conditional compilation so we don't tank nps

As expected, all of the branching in every single eval term is actually
a pretty big deal...

* Move over to new tracing everywhere

* Pull eval terms into separate file

I caved. Collocation my ass...

* Update IDEAS.md

IDEAS.md

@@ -16,7 +16,8 @@
 - [✓] Use `improving` in LMR
 - [ ] Reduce when eval is far below alpha (~delta pruning)
 - [ ] IIR when TT entry depth is much more shallow (e.g., `depth - tt_depth > 4`)
-- [ ] Cutnode reductions
+- [ ] IIR more in cutnodes
+- [ ] Cutnode LMR reductions
 
 ### Pruning
 - [✓] Delta pruning
@@ -39,9 +40,9 @@
 - [✓] Threat-based history
 
 ### Time management
-- [ ] Use less time when bestmove remains stable
-- [ ] Use less time when eval remains stable
-- [ ] Use more time when subtree has more nodes? Or less? I don't really get
+- [✓] Use less time when bestmove remains stable
+- [✓] Use less time when eval remains stable
+- [✓] Use more time when subtree has more nodes? Or less? I don't really get
       this one, tbh.
 
 ## Evaluation
@@ -128,9 +129,6 @@
 - [✓] Clear killer moves for the next ply in each node
 - [ ] Don't store killers during null-search
 - [✓] Yield killers in a fifo way (easy, since we "rotate" the moves out)
-- [ ] Have "short moves" and "long moves", where the long move includes extra
-      information (like the moved piece), so we can index all of our history 
-      table using long moves instead. (This essentially becomes our `HistIndex`.)
 - [=] Performance tweaks in hot loops:
       - [✓] Transmute between enums and integers, instead of lookups
       - [✓] forego bounds checks

simbelmyne/Cargo.toml

@@ -21,8 +21,10 @@ clap = { version = "4.4.7", features = ["derive"] }
 itertools = "0.11.0"
 rayon = "1.8.1"
 arrayvec = "0.7.4"
+bytemuck = { version = "1.16.3", features = ["derive", "min_const_generics"] }
 
 [features]
 default = ["spsa"]
 spsa = []
 wdl = []
+texel = []

simbelmyne/src/evaluate/lookups.rs

@@ -12,8 +12,6 @@ pub const FILES: BBTable = gen_files();
 
 pub const PASSED_PAWN_MASKS: [BBTable; Color::COUNT] = gen_passed_pawn_masks();
 
-pub const ISOLATED_PAWN_MASKS: BBTable = gen_isolated_pawn_masks();
-
 pub const DOUBLED_PAWN_MASKS: [Bitboard; 8] = gen_doubled_pawn_masks();
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -69,39 +67,6 @@ const fn gen_passed_pawn_masks() -> [BBTable; Color::COUNT] {
     masks
 }
 
-////////////////////////////////////////////////////////////////////////////////
-//
-// Isolated pawn masks
-//
-////////////////////////////////////////////////////////////////////////////////
-
-const fn gen_isolated_pawn_masks() -> BBTable {
-    const A_FILE: Bitboard = Bitboard(0x101010101010101);
-
-    let mut sq: usize = 0;
-
-    let mut masks = [Bitboard::EMPTY; Square::COUNT];
-
-    while sq < 64 {
-        let file = sq % 8;
-        let mut mask = 0;
-
-        if file > 0 {
-            mask |= A_FILE.0 << file - 1;
-        }
-
-        if file < 7 {
-            mask |= A_FILE.0 << file + 1;
-        }
-
-        masks[sq] = Bitboard(mask);
-
-        sq += 1;
-    }
-
-    masks
-}
-
 ////////////////////////////////////////////////////////////////////////////////
 //
 // Doubled pawn masks
@@ -162,18 +127,3 @@ fn passed_pawn_masks() {
         Bitboard(0x38383838)
     );
 }
-
-#[test]
-fn isolated_pawn_masks() {
-    use Square::*;
-
-    assert_eq!(
-        ISOLATED_PAWN_MASKS[A6], 
-        Bitboard(0x202020202020202)
-    );
-
-    assert_eq!(
-        ISOLATED_PAWN_MASKS[E4], 
-        Bitboard(0x2828282828282828)
-    );
-}