vllm/vllm/model_executor/layers/quantization/utils/quant_utils.py

"""This file is used for /tests and /benchmarks"""
from typing import List

import numpy
import torch

SUPPORTED_NUM_BITS = [4, 8]
SUPPORTED_GROUP_SIZES = [-1, 32, 64, 128]

# Note: this is a hack. We should update each model to register the
# stacked params and get it from there instead in a future PR.
# fused_name: List[shard_name]
FUSED_LAYER_NAME_MAPPING = {
    "qkv_proj": ["q_proj", "k_proj", "v_proj"],
    "gate_up_proj": ["gate_proj", "up_proj"]
}


def is_layer_skipped(prefix: str, ignored_layers: List[str]) -> bool:
    # prefix: model.layers.0.self_attn.q_proj
    # proj_name: q_proj
    proj_name = prefix.split(".")[-1]
    if proj_name in FUSED_LAYER_NAME_MAPPING:
        shard_prefixes = [
            prefix.replace(proj_name, shard_proj_name)
            for shard_proj_name in FUSED_LAYER_NAME_MAPPING[proj_name]
        ]

        is_skipped = None
        for shard_prefix in shard_prefixes:
            is_shard_skipped = shard_prefix in ignored_layers

            if is_skipped is None:
                is_skipped = is_shard_skipped
            elif is_shard_skipped != is_skipped:
                raise ValueError(
                    f"Detected some but not all shards of {prefix} "
                    "are quantized. All shards of fused layers "
                    "to have the same precision.")
    else:
        is_skipped = prefix in ignored_layers

    assert is_skipped is not None
    return is_skipped


def get_pack_factor(num_bits):
    assert num_bits in SUPPORTED_NUM_BITS, f"Unsupported num_bits = {num_bits}"
    return 32 // num_bits


def permute_rows(q_w: torch.Tensor, w_ref: torch.Tensor, group_size: int):
    assert q_w.shape == w_ref.shape

    orig_device = q_w.device
    k_size, _ = q_w.shape

    g_idx = torch.zeros((k_size, ), dtype=torch.int32)
    for i in range(k_size):
        g_idx[i] = i // group_size

    # Simulate act_order by doing a random permutation on K
    rand_perm = torch.randperm(k_size)

    g_idx = g_idx[rand_perm].contiguous()
    q_w = q_w[rand_perm, :].contiguous()
    w_ref = w_ref[rand_perm, :].contiguous()

    return (
        w_ref.to(device=orig_device),
        q_w.to(device=orig_device),
        g_idx.to(device=orig_device),
        rand_perm.to(device=orig_device),
    )


def quantize_weights(w: torch.Tensor, num_bits: int, group_size: int,
                     act_order: bool):
    orig_device = w.device
    size_k, size_n = w.shape

    assert w.is_floating_point(), "w must be float"
    assert num_bits in SUPPORTED_NUM_BITS, f"Unsupported num_bits = {num_bits}"
    assert group_size in SUPPORTED_GROUP_SIZES + [
        size_k
    ], f"Unsupported groupsize = {group_size}"

    if group_size == -1:
        group_size = size_k
    assert group_size <= size_k

    max_q_val = 2**num_bits - 1
    half_q_val = (max_q_val + 1) // 2

    # Reshape to [groupsize, -1]
    if group_size < size_k:
        w = w.reshape((-1, group_size, size_n))
        w = w.permute(1, 0, 2)
        w = w.reshape((group_size, -1))

    # Compute scale for each group
    s = torch.max(torch.abs(w), 0, keepdim=True)[0]
    s *= 2 / max_q_val  # 2 => symmetric

    # Quantize
    q_w = torch.round(w / s).int()
    q_w += half_q_val
    q_w = torch.clamp(q_w, 0, max_q_val)

    # Compute ref (dequantized)
    w_ref = (q_w - half_q_val).half() * s

    # Restore original shapes
    if group_size < size_k:

        def reshape_w(w):
            w = w.reshape((group_size, -1, size_n))
            w = w.permute(1, 0, 2)
            w = w.reshape((size_k, size_n)).contiguous()
            return w

        q_w = reshape_w(q_w)
        w_ref = reshape_w(w_ref)

    s = s.reshape((-1, size_n)).contiguous()

    # Apply act_order
    g_idx = torch.empty(0, dtype=torch.int, device=w.device)
    rand_perm = torch.empty(0, dtype=torch.int, device=w.device)
    if act_order:
        assert (
            group_size < size_k
        ), "For act_order, groupsize = {} must be less than size_k = {}".format(
            group_size, size_k)

        w_ref, q_w, g_idx, rand_perm = permute_rows(q_w, w_ref, group_size)

    return (
        w_ref.to(device=orig_device),
        q_w.to(device=orig_device),
        s.to(device=orig_device),
        g_idx.to(device=orig_device),
        rand_perm.to(device=orig_device),
    )


def quantize_weights_with_zp(w: torch.Tensor, num_bits: int, group_size: int):
    orig_device = w.device
    size_k, size_n = w.shape

    assert w.is_floating_point(), "w must be float"
    assert num_bits in SUPPORTED_NUM_BITS, f"Unsupported num_bits = {num_bits}"
    assert group_size in SUPPORTED_GROUP_SIZES + [
        size_k
    ], f"Unsupported groupsize = {group_size}"

    if group_size == -1:
        group_size = size_k
    assert group_size <= size_k

    max_q_val = 2**num_bits - 1
    min_q_val = 0

    # Reshape to [groupsize, -1]
    if group_size < size_k:
        w = w.reshape((-1, group_size, size_n))
        w = w.permute(1, 0, 2)
        w = w.reshape((group_size, -1))

    # Compute scale for each group
    max = torch.max(w, 0, keepdim=True)[0]
    min = torch.min(w, 0, keepdim=True)[0]
    s = (max - min).clamp(min=1e-5) / max_q_val

    # Compute zero-point for each group
    zp = (-torch.round(min / s)).clamp(min_q_val, max_q_val).int()

    # Quantize
    q_w = torch.round(w / s).int() + zp
    q_w = torch.clamp(q_w, min_q_val, max_q_val)

    # Compute ref (dequantized)
    w_ref = (q_w - zp).half() * s

    # Restore original shapes
    if group_size < size_k:

        def reshape_w(w):
            w = w.reshape((group_size, -1, size_n))
            w = w.permute(1, 0, 2)
            w = w.reshape((size_k, size_n)).contiguous()
            return w

        q_w = reshape_w(q_w)
        w_ref = reshape_w(w_ref)

    s = s.reshape((-1, size_n)).contiguous()
    zp = zp.reshape((-1, size_n)).contiguous()

    return (
        w_ref.to(device=orig_device),
        q_w.to(device=orig_device),
        s.to(device=orig_device),
        zp.to(device=orig_device),
    )


# QQQ employs different quant schemes for per-group and
# per-channel quantization.
def qqq_quantize_weights(w: torch.Tensor, num_bits: int, group_size: int):
    orig_device = w.device
    size_k, size_n = w.shape

    assert w.is_floating_point(), "w must be float"
    assert num_bits in SUPPORTED_NUM_BITS, f"Unsupported num_bits = {num_bits}"
    assert group_size in SUPPORTED_GROUP_SIZES + [
        size_k
    ], f"Unsupported groupsize = {group_size}"

    if group_size == -1:
        group_size = size_k
    assert group_size <= size_k

    if group_size < size_k:
        # Reshape to [groupsize, -1]
        w = w.reshape((-1, group_size, size_n))
        w = w.permute(1, 0, 2)
        w = w.reshape((group_size, -1))

        max_q_val = 2**num_bits - 1
        half_q_val = (max_q_val + 1) // 2

        # Compute scale for each group
        s_group = torch.max(torch.abs(w), 0, keepdim=True)[0]
        s_group *= 2 / max_q_val  # 2 => symmetric

        # Quantize
        q_w = torch.round(w / s_group).int()
        q_w += half_q_val
        q_w = torch.clamp(q_w, 0, max_q_val)
        # Compute ref (dequantized)
        w_ref = (q_w - half_q_val).half() * s_group

        # Restore original shapes
        def reshape_w(w):
            w = w.reshape((group_size, -1, size_n))
            w = w.permute(1, 0, 2)
            w = w.reshape((size_k, size_n)).contiguous()
            return w

        q_w = reshape_w(q_w)
        w_ref = reshape_w(w_ref)

        # Compute int8 quantization scale for each channel
        s_channel = torch.max(torch.abs(w_ref), 0, keepdim=True)[0]
        s_channel /= 127.0
        t_int8 = (w_ref / s_channel).round().clamp(-128, 127).to(torch.int8)
        w_ref = t_int8.half() * s_channel
        s_channel = s_channel.reshape(1, -1).to(dtype=torch.float)

        # Fuse scales
        s_group = (s_group.reshape(-1, size_n).contiguous() /
                   s_channel).to(dtype=torch.half)
    else:
        max_q_val = 2**(num_bits - 1) - 1

        # Compute scale for each channel
        s_channel = torch.max(torch.abs(w), 0, keepdim=True)[0]
        s_channel /= max_q_val

        # Quantize
        q_w = torch.round(w / s_channel).int()
        q_w = torch.clamp(q_w, -max_q_val, max_q_val)
        # Compute ref (dequantized)
        w_ref = q_w.half() * s_channel

        s_group = torch.tensor([], dtype=torch.half)
        # div 2 ** (8 - self.bits)) to offset right shift in unpacking
        s_channel /= (2**(8 - num_bits))
        s_channel = s_channel.reshape(-1, size_n).contiguous().to(torch.float)

    return (
        w_ref.to(device=orig_device),
        q_w.to(device=orig_device),
        s_group.to(device=orig_device),
        s_channel.to(device=orig_device),
    )


def sort_weights(q_w: torch.Tensor, g_idx: torch.Tensor):
    orig_device = q_w.device

    sort_indices = torch.argsort(g_idx).to(
        dtype=torch.int32)  # Sort based on g_idx

    g_idx = g_idx[sort_indices].contiguous()
    q_w = q_w[sort_indices, :].contiguous()

    return (
        q_w.to(device=orig_device),
        g_idx.to(device=orig_device),
        sort_indices.to(device=orig_device),
    )


def pack_rows(
    q_w: torch.Tensor,
    num_bits: int,
    size_k: int,
    size_n: int,
):
    assert q_w.shape == (size_k, size_n)

    pack_factor = get_pack_factor(num_bits)
    assert size_k % pack_factor == 0

    orig_device = q_w.device

    q_w = q_w.cpu().numpy().astype(numpy.uint32)

    q_res = numpy.zeros((size_k // pack_factor, size_n), dtype=numpy.uint32)

    for i in range(pack_factor):
        q_res |= q_w[i::pack_factor, :] << num_bits * i

    q_res = torch.from_numpy(q_res.astype(numpy.int32)).to(orig_device)
    return q_res


def pack_cols(
    q_w: torch.Tensor,
    num_bits: int,
    size_k: int,
    size_n: int,
):
    assert q_w.shape == (size_k, size_n)

    pack_factor = get_pack_factor(num_bits)
    assert size_n % pack_factor == 0

    orig_device = q_w.device

    q_w = q_w.cpu().numpy().astype(numpy.uint32)

    q_res = numpy.zeros((size_k, size_n // pack_factor), dtype=numpy.uint32)

    for i in range(pack_factor):
        q_res |= q_w[:, i::pack_factor] << num_bits * i

    q_res = torch.from_numpy(q_res.astype(numpy.int32)).to(orig_device)
    q_res = q_res.contiguous()

    return q_res


def unpack_cols(
    packed_q_w: torch.Tensor,
    num_bits: int,
    size_k: int,
    size_n: int,
):
    pack_factor = get_pack_factor(num_bits)
    assert size_n % pack_factor == 0
    assert packed_q_w.shape == (
        size_k, size_n // pack_factor
    ), "packed_q_w.shape = {} size_k = {}, size_n = {} pack_Factor = {}".format(
        packed_q_w.shape, size_k, size_n, pack_factor)

    orig_device = packed_q_w.device

    packed_q_w_cpu = packed_q_w.cpu().numpy().astype(numpy.uint32)
    q_res = numpy.zeros((size_k, size_n), dtype=numpy.uint32)

    mask = (1 << num_bits) - 1
    for i in range(pack_factor):
        vals = packed_q_w_cpu & mask
        packed_q_w_cpu >>= num_bits
        q_res[:, i::pack_factor] = vals

    q_res = torch.from_numpy(q_res.astype(numpy.int32)).to(orig_device)
    q_res = q_res.contiguous()

    return q_res


def gptq_pack(
    q_w: torch.Tensor,
    num_bits: int,
    size_k: int,
    size_n: int,
):
    return pack_rows(q_w, num_bits, size_k, size_n)


def awq_pack(
    q_w: torch.Tensor,
    num_bits: int,
    size_k: int,
    size_n: int,
):
    assert q_w.shape == (size_k, size_n)

    # Interleave column dim (for the dequantize code) and pack it to int32
    if num_bits == 4:
        interleave = numpy.array([0, 2, 4, 6, 1, 3, 5, 7])
    elif num_bits == 8:
        interleave = numpy.array([0, 2, 1, 3])
    else:
        raise Exception("num_bits must be 4 or 8, got {}".format(num_bits))

    q_w = q_w.reshape((-1, len(interleave)))[:, interleave].ravel()
    q_w = q_w.reshape((-1, size_n)).contiguous()

    return pack_cols(q_w, num_bits, size_k, size_n)