xc-llm-ascend/tests/ut/sample/test_rejection_sampler.py

#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# This file is a part of the vllm-ascend project.
#
from unittest.mock import patch

import torch

from tests.ut.base import TestBase
from vllm_ascend.sample.rejection_sampler import (
    expand_batch_to_tokens, expand_pytorch, rejection_greedy_sample_pytorch,
    rejection_random_sample_pytorch, sample_recovered_tokens_pytorch)

# Global constants
PLACEHOLDER_TOKEN_ID = -1
GREEDY_TEMPERATURE = 0.0
MAX_SPEC_LEN = 8  # Used as MAX_NUM_TOKENS in expand_batch_to_tokens


class TestAscendRejectionSampler(TestBase):

    def test_rejection_greedy_sample_pytorch(self):
        """Test greedy rejection sampling: stop when draft doesn't match, otherwise append bonus token"""
        batch_size = 2
        max_spec_len = 2
        output_token_ids = torch.full((batch_size, max_spec_len + 1),
                                      PLACEHOLDER_TOKEN_ID)

        cu_num_draft_tokens = torch.tensor([2, 4])
        num_draft_tokens = [2, 2]
        draft_token_ids = torch.tensor([10, 11, 20, 21])
        target_argmax = torch.tensor([10, 99, 20, 22])
        bonus_token_ids = torch.tensor([[100], [200]])

        is_greedy = torch.tensor([True, True])

        rejection_greedy_sample_pytorch(
            output_token_ids,
            cu_num_draft_tokens,
            draft_token_ids,
            target_argmax,
            bonus_token_ids,
            num_draft_tokens,
            max_spec_len,
            is_greedy,
        )

        assert output_token_ids[0, 0].item() == 10
        assert output_token_ids[0, 1].item() == 99
        assert output_token_ids[1, 0].item() == 20
        assert output_token_ids[1, 2].item() == PLACEHOLDER_TOKEN_ID

    def test_rejection_random_sample_pytorch(self):
        """Test random rejection sampling: accept based on uniform probability"""
        batch_size = 2
        max_spec_len = 3
        output_token_ids = torch.full((batch_size, max_spec_len + 1),
                                      PLACEHOLDER_TOKEN_ID)

        cu_num_draft_tokens = torch.tensor([2, 1])
        draft_token_ids = torch.tensor([1, 0, 2])
        draft_probs = torch.tensor([
            [0.0, 0.6, 0.0, 0.4],  # vocab_size=4
            [0.1, 0.2, 0.3, 0.4],
            [0.5, 0.5, 0.0, 0.0],
        ])
        target_probs = torch.tensor([
            [0.0, 0.8, 0.0, 0.2],
            [0.2, 0.1, 0.3, 0.4],
            [0.9, 0.1, 0.0, 0.0],
        ])
        bonus_token_ids = torch.tensor([[100], [200]])
        recovered_token_ids = torch.tensor([1, 2, 3])
        uniform_probs = torch.tensor([0.7, 0.6, 0.5])
        is_greedy = torch.tensor([False, False])
        vocab_size = 4

        rejection_random_sample_pytorch(
            output_token_ids,
            cu_num_draft_tokens,
            draft_token_ids,
            draft_probs,
            target_probs,
            bonus_token_ids,
            recovered_token_ids,
            uniform_probs,
            is_greedy,
            max_spec_len,
            vocab_size,
            IS_NGRAM=False,
        )

        assert output_token_ids[0, 0].item() == 1
        assert output_token_ids[0, 1].item() == 0
        assert output_token_ids[0, 2].item() == 100

    def test_expand_pytorch(self):
        """Test expand_pytorch functionality"""
        input_ptr = torch.tensor([10, 20, 30], dtype=torch.int32)
        cu_num_tokens_ptr = torch.tensor([2, 5, 7])
        output_ptr = torch.empty(7, dtype=torch.int32)

        expand_pytorch(
            output_ptr,
            input_ptr,
            cu_num_tokens_ptr,
            replace_from=0,
            replace_to=0,
            MAX_NUM_TOKENS=MAX_SPEC_LEN,
        )

        expected = torch.tensor([10, 10, 20, 20, 20, 30, 30])
        assert torch.equal(output_ptr, expected)

    def test_expand_batch_to_tokens(self):
        """Test expand_batch_to_tokens wrapper"""
        x = torch.tensor([10, 20, 30])
        cu_num_tokens = torch.tensor([2, 5, 7])
        num_tokens = 7

        with patch("vllm_ascend.sample.rejection_sampler.expand_pytorch"
                   ) as mock_kernel:
            expand_batch_to_tokens(x, cu_num_tokens, num_tokens)
            mock_kernel.assert_called_once()
            args = mock_kernel.call_args[0]
            assert (args[1] == x).all()
            assert (args[2] == cu_num_tokens).all()

        # Run actual function
        result = expand_batch_to_tokens(x, cu_num_tokens, num_tokens)
        expected = torch.tensor([10, 10, 20, 20, 20, 30, 30])
        assert torch.equal(result, expected)

    def test_sample_recovered_tokens_pytorch_ngram(self):
        """Test recovered token sampling under n-gram mode"""
        output_token_ids = torch.empty(2, dtype=torch.int32)
        cu_num_draft_tokens = torch.tensor([1, 2])
        draft_token_ids = torch.tensor([1, 2])
        draft_probs = None
        target_probs = torch.tensor([
            [0.1, 0.2, 0.7],
            [0.3, 0.3, 0.4],
        ])
        q = torch.tensor([
            [0.1, 0.2, 0.7],
            [0.5, 0.4, 0.1],
        ])
        vocab_size = 3

        sample_recovered_tokens_pytorch(
            output_token_ids,
            cu_num_draft_tokens,
            draft_token_ids,
            draft_probs,
            target_probs,
            q,
            vocab_size,
            IS_NGRAM=True,
        )

        assert output_token_ids[0].item() == 0
        assert output_token_ids[1].item() == 1

    def test_sample_recovered_tokens_pytorch_autoregressive(self):
        """Test recovered token sampling for autoregressive models"""
        output_token_ids = torch.empty(2, dtype=torch.int32)
        cu_num_draft_tokens = torch.tensor([1, 1])
        draft_token_ids = torch.tensor([0, 1])
        draft_probs = torch.tensor([
            [0.6, 0.1, 0.3],
            [0.2, 0.7, 0.1],
        ])
        target_probs = torch.tensor([
            [0.8, 0.1, 0.1],
            [0.3, 0.6, 0.1],
        ])
        q = torch.tensor([
            [0.5, 0.3, 0.2],
            [0.1, 0.8, 0.1],
        ])
        vocab_size = 3

        sample_recovered_tokens_pytorch(
            output_token_ids,
            cu_num_draft_tokens,
            draft_token_ids,
            draft_probs,
            target_probs,
            q,
            vocab_size,
            IS_NGRAM=False,
        )
        assert output_token_ids[0].item() == 0