Upload generation and checking scripts

scripts/generate_hf_dataset.py

@@ -6,7 +6,8 @@ Run a small test with:
 
 A full local generation uses the same format as the current dataset:
     sage -python scripts/generate_hf_dataset.py --start 0 --end 1000000000 \
-        --workers 15 --out-dir generated/sum4cubes --overwrite
+        --workers 15 --out-dir generated/sum4cubes --overwrite \
+        --merge-final-singleton
 
 Resume from a shard boundary after an interrupted run:
     sage -python scripts/generate_hf_dataset.py --start 80000000 \
@@ -103,6 +104,61 @@ def _shard_path(out_dir, shard_index):
     return out_dir / f"cubes-{shard_index:02d}.txt"
 
 
+def _last_shard_index(start, end, shard_size, merge_final_singleton):
+    if merge_final_singleton and end > start and end % shard_size == 0:
+        return (end - 1) // shard_size
+    return end // shard_size
+
+
+def _last_line(path):
+    with path.open("rb") as handle:
+        handle.seek(0, 2)
+        pos = handle.tell()
+        if pos == 0:
+            raise RuntimeError(f"empty shard {path}")
+        buf = bytearray()
+        while pos > 0:
+            step = min(8192, pos)
+            pos -= step
+            handle.seek(pos)
+            buf[:0] = handle.read(step)
+            lines = buf.splitlines()
+            if len(lines) >= 2 or pos == 0:
+                return lines[-1].decode("utf-8")
+    raise RuntimeError(f"could not read last line from {path}")
+
+
+def _merge_final_singleton(out_dir, start, end, shard_size):
+    if end <= start or end % shard_size != 0:
+        return False
+    final_index = end // shard_size
+    previous_index = final_index - 1
+    final_path = _shard_path(out_dir, final_index)
+    previous_path = _shard_path(out_dir, previous_index)
+    if not final_path.exists():
+        return False
+    if not previous_path.exists():
+        raise RuntimeError(f"missing previous shard {previous_path}")
+
+    text = final_path.read_text(encoding="utf-8")
+    lines = text.splitlines()
+    if len(lines) != 1:
+        raise RuntimeError(f"expected singleton shard {final_path}, found {len(lines)} rows")
+    n, _ = _parse_row(lines[0])
+    if n != end:
+        raise RuntimeError(f"expected final row n={end}, found n={n}")
+
+    prev_n, _ = _parse_row(_last_line(previous_path))
+    if prev_n == end:
+        final_path.unlink()
+        return True
+
+    with previous_path.open("a", encoding="utf-8") as handle:
+        handle.write(text if text.endswith("\n") else text + "\n")
+    final_path.unlink()
+    return True
+
+
 class ShardWriter:
     def __init__(self, out_dir, shard_size):
         self.out_dir = out_dir
@@ -156,10 +212,11 @@ def _parse_row(line):
     return n, xs
 
 
-def verify_generated(out_dir, start, end, shard_size):
+def verify_generated(out_dir, start, end, shard_size, merge_final_singleton=False):
     expected = start
     total = 0
-    for shard_index in range(start // shard_size, end // shard_size + 1):
+    last_shard = _last_shard_index(start, end, shard_size, merge_final_singleton)
+    for shard_index in range(start // shard_size, last_shard + 1):
         path = _shard_path(out_dir, shard_index)
         if not path.exists():
             raise RuntimeError(f"missing shard {path}")
@@ -201,6 +258,12 @@ def main():
         help="keep existing shards and continue writing from --start",
     )
     parser.add_argument("--verify-output", action="store_true")
+    parser.add_argument(
+        "--merge-final-singleton",
+        action="store_true",
+        help="if --end falls on a shard boundary, append that singleton row "
+        "to the previous shard",
+    )
     parser.add_argument("--progress-every", type=int, default=100_000)
     args = parser.parse_args()
 
@@ -312,8 +375,18 @@ def main():
         flush=True,
     )
 
+    if args.merge_final_singleton:
+        if _merge_final_singleton(out_dir, args.start, args.end, args.shard_size):
+            print("MERGE_FINAL_SINGLETON ok", flush=True)
+
     if args.verify_output:
-        checked = verify_generated(out_dir, args.start, args.end, args.shard_size)
+        checked = verify_generated(
+            out_dir,
+            args.start,
+            args.end,
+            args.shard_size,
+            args.merge_final_singleton,
+        )
         print(f"VERIFY ok rows={checked}", flush=True)