scripts: add the RX 580 benchmark harness

Encodes the production config, fixed corpus slices, repeat/median discipline
and the noise floor, so the measurement method does not have to be
rediscovered each time. Runs the corpus prefill test through llama-server and
the llama-bench sweep as a controlled cross-check, with interleaved A/B.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PZz44SLQvTXMyWGio6t9DZ

scripts/rx580-bench/lbsweep.sh

@@ -0,0 +1,69 @@
+#!/bin/sh
+#
+# llama-bench sweep, the controlled cross-check for the corpus harness.
+# Runs ON THE POD. Normally invoked by bench.sh.
+#
+# Usage: lbsweep.sh <build_dir> <label>
+# Env overrides: RESULTS, MODEL, LB_P, LB_N, LB_R
+#
+# Everything that must be compared lives inside ONE llama-bench invocation
+# (-p takes a comma-separated list), because cross-invocation variance on this
+# box is about 7 percent while the within-run error bars are about 0.3 percent.
+#
+# Flag traps, learned the hard way:
+#   * -tb is NOT a llama-bench flag. It exists on llama-server only.
+#   * -ncmoe is the llama-bench spelling of --n-cpu-moe.
+#   * -mmp 0 is the llama-bench equivalent of the server's --no-mmap.
+#   * A bad flag makes llama-bench print usage and exit silently, which looks
+#     exactly like a sweep that produced no rows. Always check row count.
+#   * A ubatch larger than -p never fills, so keep -p a multiple of -ub.
+#
+set -e
+BUILD_DIR="$1"
+LABEL="$2"
+if [ -z "$BUILD_DIR" ] || [ -z "$LABEL" ]; then
+  echo "usage: $0 <build_dir> <label>" >&2
+  exit 2
+fi
+
+RESULTS="${RESULTS:-/root/bench/results.txt}"
+MODEL="${MODEL:-/root/.cache/huggingface/hub/models--unsloth--Qwen3.6-35B-A3B-GGUF/snapshots/a483e9e6cbd595906af30beda3187c2663a1118c/Qwen3.6-35B-A3B-UD-Q4_K_XL.gguf}"
+LB_P="${LB_P:-2048,8192}"
+LB_N="${LB_N:-32}"
+LB_R="${LB_R:-3}"
+
+STAMP=$(date -u +%Y-%m-%dT%H:%M:%S)
+export LD_LIBRARY_PATH="$BUILD_DIR/bin"
+export LABEL BUILD_DIR STAMP RESULTS
+
+OUT=$("$BUILD_DIR/bin/llama-bench" \
+  -m "$MODEL" \
+  -t 6 -ngl 99 -ncmoe 40 -b 2048 -ub 2048 -fa 1 -mmp 0 \
+  -p "$LB_P" -n "$LB_N" -r "$LB_R" -o json 2>/dev/null)
+
+if [ -z "$OUT" ]; then
+  echo "ERROR: llama-bench produced no output for $LABEL (bad flag?)" >&2
+  exit 3
+fi
+
+printf '%s' "$OUT" | python3 -c '
+import json, sys, os
+label = os.environ["LABEL"]
+build = os.environ["BUILD_DIR"]
+stamp = os.environ["STAMP"]
+results = os.environ["RESULTS"]
+rows = json.load(sys.stdin)
+if not rows:
+    sys.stderr.write("ERROR: llama-bench returned zero rows\n")
+    sys.exit(3)
+out = open(results, "a")
+for r in rows:
+    test = "pp%d" % r["n_prompt"] if r["n_prompt"] else "tg%d" % r["n_gen"]
+    line = ("LBRESULT label=%s build=%s test=%s tps=%.2f stddev=%.2f "
+            "samples=%s time=%s"
+            % (label, build, test, r["avg_ts"], r["stddev_ts"],
+               r["samples_ts"], stamp))
+    out.write(line + "\n")
+    print(line)
+out.close()
+'