From 3c31f900eaf249c5c8865b06fe33081de7c09361 Mon Sep 17 00:00:00 2001
From: Eryn Wells <eryn@erynwells.me>
Date: Wed, 11 Jun 2025 08:16:37 -0700
Subject: [PATCH] [perft] A script that checks a list of positions against
 known node counts

A small Python script that reads a JSON list of positions and their known Perft
node counts to a certain depth, then invokes the Perft program for each position
and validates the output.

Peter Ellis Jones shared such a JSON list on GitHub. Import that file.
---
 .../data/peterellisjones-perft-positions.json | 117 ++++++++++++++++++
 perft/scripts/check-positions                 |  80 ++++++++++++
 2 files changed, 197 insertions(+)
 create mode 100644 perft/data/peterellisjones-perft-positions.json
 create mode 100755 perft/scripts/check-positions

diff --git a/perft/data/peterellisjones-perft-positions.json b/perft/data/peterellisjones-perft-positions.json
new file mode 100644
index 0000000..eb48f34
--- /dev/null
+++ b/perft/data/peterellisjones-perft-positions.json
@@ -0,0 +1,117 @@
+[
+   {
+      "depth":1,
+      "nodes":8,
+      "fen":"r6r/1b2k1bq/8/8/7B/8/8/R3K2R b KQ - 3 2"
+   },
+   {
+      "depth":1,
+      "nodes":8,
+      "fen":"8/8/8/2k5/2pP4/8/B7/4K3 b - d3 0 3"
+   },
+   {
+      "depth":1,
+      "nodes":19,
+      "fen":"r1bqkbnr/pppppppp/n7/8/8/P7/1PPPPPPP/RNBQKBNR w KQkq - 2 2"
+   },
+   {
+      "depth":1,
+      "nodes":5,
+      "fen":"r3k2r/p1pp1pb1/bn2Qnp1/2qPN3/1p2P3/2N5/PPPBBPPP/R3K2R b KQkq - 3 2"
+   },
+   {
+      "depth":1,
+      "nodes":44,
+      "fen":"2kr3r/p1ppqpb1/bn2Qnp1/3PN3/1p2P3/2N5/PPPBBPPP/R3K2R b KQ - 3 2"
+   },
+   {
+      "depth":1,
+      "nodes":39,
+      "fen":"rnb2k1r/pp1Pbppp/2p5/q7/2B5/8/PPPQNnPP/RNB1K2R w KQ - 3 9"
+   },
+   {
+      "depth":1,
+      "nodes":9,
+      "fen":"2r5/3pk3/8/2P5/8/2K5/8/8 w - - 5 4"
+   },
+   {
+      "depth":3,
+      "nodes":62379,
+      "fen":"rnbq1k1r/pp1Pbppp/2p5/8/2B5/8/PPP1NnPP/RNBQK2R w KQ - 1 8"
+   },
+   {
+      "depth":3,
+      "nodes":89890,
+      "fen":"r4rk1/1pp1qppp/p1np1n2/2b1p1B1/2B1P1b1/P1NP1N2/1PP1QPPP/R4RK1 w - - 0 10"
+   },
+   {
+      "depth":6,
+      "nodes":1134888,
+      "fen":"3k4/3p4/8/K1P4r/8/8/8/8 b - - 0 1"
+   },
+   {
+      "depth":6,
+      "nodes":1015133,
+      "fen":"8/8/4k3/8/2p5/8/B2P2K1/8 w - - 0 1"
+   },
+   {
+      "depth":6,
+      "nodes":1440467,
+      "fen":"8/8/1k6/2b5/2pP4/8/5K2/8 b - d3 0 1"
+   },
+   {
+      "depth":6,
+      "nodes":661072,
+      "fen":"5k2/8/8/8/8/8/8/4K2R w K - 0 1"
+   },
+   {
+      "depth":6,
+      "nodes":803711,
+      "fen":"3k4/8/8/8/8/8/8/R3K3 w Q - 0 1"
+   },
+   {
+      "depth":4,
+      "nodes":1274206,
+      "fen":"r3k2r/1b4bq/8/8/8/8/7B/R3K2R w KQkq - 0 1"
+   },
+   {
+      "depth":4,
+      "nodes":1720476,
+      "fen":"r3k2r/8/3Q4/8/8/5q2/8/R3K2R b KQkq - 0 1"
+   },
+   {
+      "depth":6,
+      "nodes":3821001,
+      "fen":"2K2r2/4P3/8/8/8/8/8/3k4 w - - 0 1"
+   },
+   {
+      "depth":5,
+      "nodes":1004658,
+      "fen":"8/8/1P2K3/8/2n5/1q6/8/5k2 b - - 0 1"
+   },
+   {
+      "depth":6,
+      "nodes":217342,
+      "fen":"4k3/1P6/8/8/8/8/K7/8 w - - 0 1"
+   },
+   {
+      "depth":6,
+      "nodes":92683,
+      "fen":"8/P1k5/K7/8/8/8/8/8 w - - 0 1"
+   },
+   {
+      "depth":6,
+      "nodes":2217,
+      "fen":"K1k5/8/P7/8/8/8/8/8 w - - 0 1"
+   },
+   {
+      "depth":7,
+      "nodes":567584,
+      "fen":"8/k1P5/8/1K6/8/8/8/8 w - - 0 1"
+   },
+   {
+      "depth":4,
+      "nodes":23527,
+      "fen":"8/8/2k5/5q2/5n2/8/5K2/8 b - - 0 1"
+   }
+]
\ No newline at end of file
diff --git a/perft/scripts/check-positions b/perft/scripts/check-positions
new file mode 100755
index 0000000..8258567
--- /dev/null
+++ b/perft/scripts/check-positions
@@ -0,0 +1,80 @@
+#!/usr/bin/env python3
+# Eryn Wells <eryn@erynwells.me>
+
+'''
+New script.
+'''
+
+import argparse
+import json
+import subprocess
+
+
+def run_perft(fen, depth, expected_nodes_count):
+    result = subprocess.run(
+        [
+            'cargo',
+            'run',
+            '--',
+            '--fen', fen,
+            str(depth)
+        ],
+        capture_output=True,
+        check=True,
+        text=True
+    )
+
+    nodes_count = 0
+    for line in result.stdout.splitlines():
+        if line.startswith('nodes='):
+            (_, nodes_count) = line.split('=')
+            nodes_count = int(nodes_count)
+
+    return nodes_count
+
+
+def parse_args(argv, *a, **kw):
+    parser = argparse.ArgumentParser(*a, **kw)
+    parser.add_argument('-c', '--continue', dest='should_continue',
+                        action='store_true')
+    parser.add_argument('file')
+    args = parser.parse_args(argv)
+    return args
+
+
+def main(argv):
+    args = parse_args(argv[1:], prog=argv[0])
+
+    items = []
+    with open(args.file, 'r') as f:
+        items = json.load(f)
+
+    should_continue = args.should_continue
+
+    for item in items:
+        fen = item['fen']
+        depth = item['depth']
+        expected_nodes_count = int(item['nodes'])
+
+        print('---')
+        print(f'fen={fen}')
+        print(f'expected-nodes={expected_nodes_count}')
+
+        nodes_count = run_perft(fen, depth, expected_nodes_count)
+        print(f'nodes={nodes_count}')
+
+        did_pass = nodes_count == expected_nodes_count
+        if did_pass:
+            print('result=PASS')
+        else:
+            print('result=FAIL')
+
+        if not did_pass and not should_continue:
+            return -1
+        
+    return 0 
+
+
+if __name__ == '__main__':
+    import sys
+    sys.exit(main(sys.argv))