test_fp8_quant_group.py

# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
"""Tests for QuantFP8 Group Quantization implementation."""

import pytest
import torch

from vllm.model_executor.layers.quantization.input_quant_fp8 import QuantFP8
from vllm.model_executor.layers.quantization.utils.quant_utils import GroupShape
from vllm.platforms import current_platform


@pytest.mark.parametrize(
    "batch_size,hidden_dim,group_size",
    [
        (16, 256, 32),  # Small
        (64, 1024, 64),  # Medium
        (128, 2048, 128),  # Large
        (8, 513, 64),  # Non-divisible (native only)
    ],
)
@pytest.mark.parametrize("seed", [42])
@pytest.mark.parametrize("use_ue8m0", [True, False])
@torch.inference_mode()
def test_quantfp8_group_functionality(
    batch_size: int, hidden_dim: int, group_size: int, seed: int, use_ue8m0: bool
) -> None:
    """Test QuantFP8 group quantization with various configurations.

    Tests both CUDA and native implementations, column-major scales,
    and verifies consistency between implementations.
    """
    current_platform.seed_everything(seed)

    x = torch.randn((batch_size, hidden_dim), dtype=torch.bfloat16, device="cuda") * 8
    expected_num_groups = (hidden_dim + group_size - 1) // group_size
    is_divisible = hidden_dim % group_size == 0

    group_shape = GroupShape(1, group_size)
    quant_op = QuantFP8(
        static=False,
        group_shape=group_shape,
        column_major_scales=False,
        use_ue8m0=use_ue8m0,
    )

    # 1. Test native implementation (always available)
    x_quant_native, scales_native = quant_op.forward_native(x.clone())
    assert x_quant_native.shape == x.shape
    assert scales_native.shape == (batch_size, expected_num_groups)

    # 2. Test column-major scales configuration
    quant_op_col = QuantFP8(
        static=False,
        group_shape=group_shape,
        column_major_scales=True,
        use_ue8m0=use_ue8m0,
    )
    _, scales_col = quant_op_col.forward_native(x.clone())
    assert scales_col.shape == (batch_size, expected_num_groups)
    assert scales_col.stride(0) == 1
    assert scales_col.stride(1) == batch_size

    # Test column-major scales consistency
    assert torch.allclose(scales_col, scales_native, rtol=1e-9, atol=1e-8)

    # 3. Test CUDA implementation (only for divisible dimensions)
    if is_divisible:
        x_quant_cuda, scales_cuda = quant_op.forward_cuda(x.clone())
        assert x_quant_cuda.shape == x.shape
        assert scales_cuda.shape == (batch_size, expected_num_groups)

        # Verify CUDA/native consistency
        assert torch.allclose(scales_cuda, scales_native, rtol=1e-9, atol=1e-8)

        # Quantized values should mostly match
        diff_count = (x_quant_cuda != x_quant_native).sum().item()
        diff_ratio = diff_count / x_quant_cuda.numel()
        assert diff_ratio < 0.002, f"Too many differences: {diff_ratio:.4%}"


@pytest.mark.parametrize("seed", [42])
@pytest.mark.parametrize("use_ue8m0", [True, False])
@torch.inference_mode()
def test_quantfp8_group_multidimensional(seed: int, use_ue8m0: bool) -> None:
    current_platform.seed_everything(seed)

    group_size = 64

    # Test with 3D input
    batch1, batch2, hidden_dim = 4, 8, 1024
    x_3d = (
        torch.randn((batch1, batch2, hidden_dim), dtype=torch.bfloat16, device="cuda")
        * 8
    )

    group_shape = GroupShape(1, group_size)
    quant_op = QuantFP8(
        static=False,
        group_shape=group_shape,
        column_major_scales=False,
        use_ue8m0=use_ue8m0,
    )

    x_quant, scales = quant_op.forward_native(x_3d.clone())
    assert x_quant.shape == x_3d.shape
    assert scales.shape == (batch1, batch2, hidden_dim // group_size)

    # Test column_major_scales with multi-dim
    quant_op_col = QuantFP8(
        static=False,
        group_shape=group_shape,
        column_major_scales=True,
        use_ue8m0=use_ue8m0,
    )
    _, scales_col = quant_op_col.forward_native(x_3d.clone())
    assert scales_col.shape == (batch1, batch2, hidden_dim // group_size)

    # Test with 4D input
    batch1, batch2, batch3, hidden_dim = 2, 3, 4, 256
    x_4d = (
        torch.randn(
            (batch1, batch2, batch3, hidden_dim), dtype=torch.bfloat16, device="cuda"
        )
        * 8
    )

    x_quant_4d, scales_4d = quant_op.forward_native(x_4d.clone())
    assert x_quant_4d.shape == x_4d.shape
    assert scales_4d.shape == (batch1, batch2, batch3, hidden_dim // group_size)

    _, scales_4d_col = quant_op_col.forward_native(x_4d.clone())
    assert scales_4d_col.shape == (batch1, batch2, hidden_dim // group_size, batch3)


@pytest.mark.parametrize("seed", [42])
@torch.inference_mode()
def test_quantfp8_group_edge_cases(seed: int) -> None:
    current_platform.seed_everything(seed)

    batch_size = 16
    group_size = 64

    # Test with single group (group_size >= hidden_dim)
    x_small = torch.randn((batch_size, 32), dtype=torch.bfloat16, device="cuda") * 8
    group_shape = GroupShape(1, group_size)
    quant_op = QuantFP8(
        static=False, group_shape=group_shape, column_major_scales=False
    )

    x_quant_small, scales_small = quant_op.forward_native(x_small.clone())
    assert x_quant_small.shape == x_small.shape
    assert scales_small.shape == (batch_size, 1)

    # Test with zero inputs
    x_zero = torch.zeros((batch_size, 256), dtype=torch.bfloat16, device="cuda")
    x_quant_zero, scales_zero = quant_op.forward_native(x_zero.clone())
    assert x_quant_zero.shape == x_zero.shape
    assert (scales_zero > 0).all(), "Scales should be clamped to minimum"

    # Test very large values
    x_large = torch.full((batch_size, 256), 1000.0, dtype=torch.bfloat16, device="cuda")
    x_quant_large, scales_large = quant_op.forward_native(x_large.clone())
    assert x_quant_large.shape == x_large.shape
    # FP8 max is typically 448 or 224, so scales should be > 1
    assert (scales_large > 1.0).all(), "Large values should have scales > 1"