llama.cpp/tools/server/tests/unit/test_ctx_shift.py

import pytest
from utils import *

server = ServerPreset.tinyllama2()


LONG_TEXT = """
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur.
Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
""".strip()

@pytest.fixture(scope="module", autouse=True)
def create_server():
    global server
    server = ServerPreset.tinyllama2()
    server.n_ctx = 256
    server.n_slots = 2


def test_ctx_shift_enabled():
    # the prompt is 301 tokens
    # the slot context is 256/2 = 128 tokens
    # the prompt is truncated to keep the last 109 tokens
    # 64 tokens are generated thanks to shifting the context when it gets full
    global server
    server.start()
    res = server.make_request("POST", "/completion", data={
        "n_predict": 64,
        "prompt": LONG_TEXT,
    })
    assert res.status_code == 200
    assert res.body["timings"]["prompt_n"] == 109
    assert res.body["timings"]["predicted_n"] == 64
    assert res.body["truncated"] is True


@pytest.mark.parametrize("n_predict,n_token_output,truncated", [
    (64, 64, False),
    (-1, 120, True),
])
def test_ctx_shift_disabled_short_prompt(n_predict: int, n_token_output: int, truncated: bool):
    global server
    server.disable_ctx_shift = True
    server.n_predict = -1
    server.start()
    res = server.make_request("POST", "/completion", data={
        "n_predict": n_predict,
        "prompt": "Hi how are you",
    })
    assert res.status_code == 200
    assert res.body["timings"]["predicted_n"] == n_token_output
    assert res.body["truncated"] == truncated


def test_ctx_shift_disabled_long_prompt():
    global server
    server.disable_ctx_shift = True
    server.start()
    res = server.make_request("POST", "/completion", data={
        "n_predict": 64,
        "prompt": LONG_TEXT,
    })
    assert res.status_code != 200
    assert "error" in res.body
    assert "exceeds the available context size" in res.body["error"]["message"]

def test_ctx_shift_disabled_stream():
    global server
    server.disable_ctx_shift = True
    server.start()
    res = server.make_stream_request("POST", "/v1/completions", data={
        "n_predict": 256,
        "prompt": "Once",
        "stream": True,
    })
    content = ""
    for data in res:
        choice = data["choices"][0]
        if choice["finish_reason"] == "length":
            assert len(content) > 0
        else:
            assert choice["finish_reason"] is None
            content += choice["text"]