prain: warm-up and draft measurement scripts

scripts/warm_effect.py

@@ -0,0 +1,38 @@
+"""Time to first token for a fresh prompt: cold, and warmed up as if it had been typed.
+
+usage (prain installed): python3 scripts/warm_effect.py http://127.0.0.1:8000
+"""
+
+import sys
+import time
+import uuid
+
+from prain.chat import chat_body, first_model, post, stream_text, warm_body
+
+PROMPT = ("You are reviewing a design for a home server that runs a mixture-of-experts language "
+          "model on a single consumer graphics card with eight gigabytes of memory. The model has "
+          "thirty layers with one hundred and twenty-eight experts each, and only a few experts per "
+          "layer fit on the card at once. The rest wait in system memory or on an NVMe drive and "
+          "are copied over PCI Express when a token needs them. List the three biggest risks of "
+          "this design and, for each, one concrete way to measure it.")
+
+
+def first_token_seconds(base_url, model, text):
+    start = time.monotonic()
+    body = chat_body(model, [{"role": "user", "content": text}], max_tokens=1)
+    with post(base_url, "/v1/chat/completions", body) as response:
+        next(stream_text(response), None)
+    return time.monotonic() - start
+
+
+def main(base_url):
+    model = first_model(base_url)
+    cold = first_token_seconds(base_url, model, f"[{uuid.uuid4().hex[:8]}] {PROMPT}")
+    text = f"[{uuid.uuid4().hex[:8]}] {PROMPT}"  # a new tag: no prefix-cache hit from above
+    post(base_url, "/v1/chat/completions", warm_body(model, [], text[:-40])).read()
+    warm = first_token_seconds(base_url, model, text)
+    print(f"first token: cold {cold:.2f} s, warmed {warm:.2f} s")
+
+
+if __name__ == "__main__":
+    main(sys.argv[1])