flash-attention/flash_attn/ops/layer_norm.py

376 lines
19 KiB
Python

# Copyright (c) 2022, Tri Dao.
# Adapted from https://github.com/NVIDIA/apex/blob/master/apex/contrib/layer_norm/layer_norm.py
import torch
from torch.nn import init
import dropout_layer_norm
def maybe_align(x, alignment_in_bytes=16):
"""Assume that x already has last dim divisible by alignment_in_bytes
"""
# TD [2023-07-04] I'm not 100% sure that clone will align the memory
# https://discuss.pytorch.org/t/how-to-ensure-that-tensor-data-ptr-is-aligned-to-16-bytes/183440
return x if x.data_ptr() % alignment_in_bytes == 0 else x.clone()
def _dropout_add_layer_norm_forward(x0, residual, gamma, beta, rowscale, colscale, dropout_p,
epsilon, residual_in_fp32=False, is_rms_norm=False):
""" Assume that arguments are contiguous and aligned to 16 bytes
"""
hidden_size = gamma.numel()
x0mat = x0.view((-1, hidden_size))
residualmat = residual.view((-1, hidden_size)) if residual is not None else None
rowscale = rowscale.view(-1) if rowscale is not None else None
zmat, xmat, dmask, mu, rsigma = dropout_layer_norm.dropout_add_ln_fwd(
x0mat, residualmat, gamma, beta, rowscale, colscale, None, None, dropout_p, epsilon,
1.0, 0, None, residual_in_fp32, is_rms_norm
)
# dmask is None if dropout_p == 0.0
# xmat is None if dropout_p == 0.0 and residual is None and residual_dtype != input_dtype
return zmat, xmat if xmat is not None else x0mat, dmask, mu, rsigma
def _dropout_add_layer_norm_backward(dz, dx, x, x0, dmask, mu, rsigma, gamma, rowscale, colscale,
dropout_p, has_residual, is_rms_norm=False):
""" Assume that arguments are contiguous and aligned to 16 bytes
dx == None means that it was a post-norm architecture
(x = drop(x0) + residual was not returned in the fwd).
x0 must not be None if we have colscale.
"""
hidden_size = gamma.numel()
xmat = x.view((-1, hidden_size))
dzmat = dz.view(xmat.shape)
dxmat = dx.view(xmat.shape) if dx is not None else None
x0mat = x0.view((-1, hidden_size)) if x0 is not None else None
rowscale = rowscale.view(-1) if rowscale is not None else None
if colscale is not None:
assert x0 is not None, 'x0 is required to compute the gradient of colscale'
dx0mat, dresidualmat, dgamma, dbeta, _, _, *rest = dropout_layer_norm.dropout_add_ln_bwd(
dzmat, dxmat, xmat, x0mat, dmask, mu, rsigma, gamma, rowscale, colscale, None, None,
dropout_p, 1.0, 0, has_residual, is_rms_norm
)
# dresidualmat is None if not has_residual
if colscale is None:
return dx0mat, dresidualmat, dgamma, dbeta
else:
dcolscale = rest[0]
return dx0mat, dresidualmat, dgamma, dbeta, dcolscale
def _dropout_add_layer_norm_subset_forward(x0, residual, gamma, beta, colscale, x0_subset,
out_subset, dropout_p, epsilon, rowscale_const,
out_numrows, residual_in_fp32=False, is_rms_norm=False):
""" Assume that arguments are contiguous and aligned to 16 bytes
"""
hidden_size = gamma.numel()
x0mat = x0.view((-1, hidden_size))
residualmat = residual.view((-1, hidden_size)) if residual is not None else None
x0_subset = x0_subset.view(-1) if x0_subset is not None else None
out_subset = out_subset.view(-1) if out_subset is not None else None
zmat, xmat, dmask, mu, rsigma = dropout_layer_norm.dropout_add_ln_fwd(
x0mat, residualmat, gamma, beta, None, colscale, x0_subset, out_subset, dropout_p, epsilon,
rowscale_const, out_numrows, None, residual_in_fp32, is_rms_norm
)
# dmask is None if dropout_p == 0.0
# xmat is None if dropout_p == 0.0 and residual is None and residual_dtype != input_dtype
return zmat, xmat if xmat is not None else x0mat, dmask, mu, rsigma
def _dropout_add_layer_norm_subset_backward(dz, dx, x, x0, dmask, mu, rsigma, gamma, colscale,
x0_subset, out_subset, dropout_p, rowscale_const,
x0_numrows, has_residual, is_rms_norm=False):
""" Assume that arguments are contiguous and aligned to 16 bytes
dx == None means that it was a post-norm architecture
(x = drop(x0) + residual was not returned in the fwd).
x0 must not be None if we have colscale.
"""
hidden_size = gamma.numel()
xmat = x.view((-1, hidden_size))
dzmat = dz.view(-1, hidden_size)
dxmat = dx.view(xmat.shape) if dx is not None else None
x0mat = x0.view((-1, hidden_size)) if x0 is not None else None
x0_subset = x0_subset.view(-1) if x0_subset is not None else None
out_subset = out_subset.view(-1) if out_subset is not None else None
if colscale is not None:
assert x0 is not None, 'x0 is required to compute the gradient of colscale'
dx0mat, dresidualmat, dgamma, dbeta, _, _, *rest = dropout_layer_norm.dropout_add_ln_bwd(
dzmat, dxmat, xmat, x0mat, dmask, mu, rsigma, gamma, None, colscale, x0_subset, out_subset,
dropout_p, rowscale_const, x0_numrows, has_residual, is_rms_norm
)
# dresidualmat is None if not has_residual
if colscale is None:
return dx0mat, dresidualmat, dgamma, dbeta
else:
dcolscale = rest[0]
return dx0mat, dresidualmat, dgamma, dbeta, dcolscale
def _dropout_add_layer_norm_parallel_residual_forward(
x0, x1, residual, gamma0, beta0, gamma1, beta1, dropout_p,
epsilon, residual_in_fp32=False, is_rms_norm=False
):
""" Assume that arguments are contiguous and aligned to 16 bytes
"""
hidden_size = gamma0.numel()
x0mat = x0.view((-1, hidden_size))
x1mat = x1.view((-1, hidden_size)) if x1 is not None else None
residualmat = residual.view((-1, hidden_size)) if residual is not None else None
z0mat, z1mat, xmat, dmask0, dmask1, mu, rsigma = dropout_layer_norm.dropout_add_ln_parallel_residual_fwd(
x0mat, x1mat, residualmat, gamma0, beta0, gamma1, beta1, dropout_p, epsilon,
None, residual_in_fp32, is_rms_norm
)
# dmask0 and dmask1 are None if dropout_p == 0.0
# xmat is None if dropout_p == 0.0 and residual is None and residual_dtype != input_dtype
return z0mat, z1mat, xmat if xmat is not None else x0mat, dmask0, dmask1, mu, rsigma
def _dropout_add_layer_norm_parallel_residual_backward(
dz0, dz1, dx, x, dmask0, dmask1, mu, rsigma, gamma0, gamma1,
dropout_p, has_x1, has_residual, is_rms_norm=False
):
""" Assume that arguments are contiguous and aligned to 16 bytes
dx == None means that it was a post-norm architecture
(x = drop(x0) + residual was not returned in the fwd).
"""
hidden_size = gamma0.numel()
xmat = x.view((-1, hidden_size))
dz0mat = dz0.view(xmat.shape)
dz1mat = dz1.view(xmat.shape) if dz1 is not None else None
dxmat = dx.view(xmat.shape) if dx is not None else None
dx0mat, dx1mat, dresidualmat, dgamma0, dbeta0, dgamma1, dbeta1, *rest = dropout_layer_norm.dropout_add_ln_parallel_residual_bwd(
dz0mat, dz1mat, dxmat, xmat, dmask0, dmask1, mu, rsigma, gamma0, gamma1,
dropout_p, has_x1, has_residual, is_rms_norm
)
# dresidualmat is None if not has_residual
return dx0mat, dx1mat, dresidualmat, dgamma0, dbeta0, dgamma1, dbeta1
class DropoutAddLayerNormFn(torch.autograd.Function):
@staticmethod
def forward(ctx, x0, residual, gamma, beta, rowscale, colscale, dropout_p, epsilon,
residual_in_fp32=False, prenorm=False, is_rms_norm=False, return_dmask=False):
x0 = maybe_align(x0.contiguous(), 16)
residual = maybe_align(residual.contiguous(), 16) if residual is not None else None
gamma = maybe_align(gamma.contiguous(), 16)
beta = maybe_align(beta.contiguous(), 16) if beta is not None else None
rowscale = maybe_align(rowscale.contiguous(), 16) if rowscale is not None else None
colscale = maybe_align(colscale.contiguous(), 16) if colscale is not None else None
zmat, xmat, dmask, mu, rsigma = _dropout_add_layer_norm_forward(
x0, residual, gamma, beta, rowscale, colscale, dropout_p, epsilon,
residual_in_fp32, is_rms_norm
)
# Only need to save x0 if we need to compute gradient wrt colscale
x0_saved = x0 if colscale is not None else None
ctx.save_for_backward(xmat.view(x0.shape), x0_saved, dmask, gamma, mu, rsigma, rowscale, colscale)
ctx.prenorm = prenorm
ctx.dropout_p = dropout_p
ctx.has_residual = residual is not None
ctx.is_rms_norm = is_rms_norm
ctx.has_beta = beta is not None
if not return_dmask:
return (zmat.view(x0.shape) if not prenorm
else (zmat.view(x0.shape), xmat.view(x0.shape)))
else:
dmask = (dmask.view(x0.shape) if dropout_p > 0.
else torch.ones(x0.shape, dtype=torch.uint8, device=x0.device))
ctx.mark_non_differentiable(dmask)
return ((zmat.view(x0.shape), dmask) if not prenorm
else (zmat.view(x0.shape), xmat.view(x0.shape), dmask))
@staticmethod
def backward(ctx, dz, *args):
# assert dz.is_contiguous()
dz = maybe_align(dz.contiguous(), 16) # this happens!
dx = maybe_align(args[0].contiguous(), 16) if ctx.prenorm else None
x, x0, dmask, gamma, mu, rsigma, rowscale, colscale = ctx.saved_tensors
# x0 is None if colscale is None
dropout_p = ctx.dropout_p
has_residual = ctx.has_residual
dx0mat, dresidualmat, dgamma, dbeta, *rest = _dropout_add_layer_norm_backward(
dz, dx, x, x0, dmask, mu, rsigma, gamma, rowscale, colscale, dropout_p, has_residual,
ctx.is_rms_norm
)
dx0 = dx0mat.view(x.shape)
dresidual = dresidualmat.view(x.shape) if dresidualmat is not None else None
dcolscale = rest[0] if colscale is not None else None
return (dx0, dresidual, dgamma, dbeta if ctx.has_beta else None, None, dcolscale, None,
None, None, None, None, None)
class DropoutAddLayerNormSubsetFn(torch.autograd.Function):
@staticmethod
def forward(ctx, x0, residual, gamma, beta, colscale, x0_subset, out_subset, dropout_p, epsilon,
rowscale_const, out_numrows, residual_in_fp32=False,
prenorm=False, is_rms_norm=False, return_dmask=False):
x0 = maybe_align(x0.contiguous(), 16)
residual = maybe_align(residual.contiguous(), 16) if residual is not None else None
gamma = maybe_align(gamma.contiguous(), 16)
beta = maybe_align(beta.contiguous(), 16) if beta is not None else None
colscale = maybe_align(colscale.contiguous(), 16) if colscale is not None else None
zmat, xmat, dmask, mu, rsigma = _dropout_add_layer_norm_subset_forward(
x0, residual, gamma, beta, colscale, x0_subset, out_subset, dropout_p, epsilon,
rowscale_const, out_numrows, residual_in_fp32, is_rms_norm
)
# Only need to save x0 if we need to compute gradient wrt colscale
x0_saved = x0 if colscale is not None else None
x_shape = (-1, *x0.shape[1:])
ctx.save_for_backward(xmat.view(x_shape), x0_saved, dmask, gamma, mu, rsigma, colscale,
x0_subset, out_subset)
ctx.prenorm = prenorm
ctx.dropout_p = dropout_p
ctx.rowscale_const = rowscale_const
ctx.x0_numrows = x0.shape[:-1].numel()
ctx.has_residual = residual is not None
ctx.is_rms_norm = is_rms_norm
ctx.has_beta = beta is not None
z_shape = (-1, *x0.shape[1:])
if not return_dmask:
return (zmat.view(z_shape) if not prenorm
else (zmat.view(z_shape), xmat.view(x0.shape)))
else:
z = zmat.view(z_shape)
dmask = (dmask.view(x0.shape) if dropout_p > 0.
else torch.ones(x0.shape, dtype=torch.uint8, device=x0.device))
ctx.mark_non_differentiable(dmask)
return ((z, dmask) if not prenorm else (z, xmat.view(x_shape), dmask))
@staticmethod
def backward(ctx, dz, *args):
# assert dz.is_contiguous()
dz = maybe_align(dz.contiguous(), 16) # this happens!
dx = maybe_align(args[0].contiguous(), 16) if ctx.prenorm else None
x, x0, dmask, gamma, mu, rsigma, colscale, x0_subset, out_subset = ctx.saved_tensors
# x0 is None if colscale is None
dropout_p = ctx.dropout_p
has_residual = ctx.has_residual
dx0mat, dresidualmat, dgamma, dbeta, *rest = _dropout_add_layer_norm_subset_backward(
dz, dx, x, x0, dmask, mu, rsigma, gamma, colscale, x0_subset, out_subset, dropout_p,
ctx.rowscale_const, ctx.x0_numrows, has_residual, ctx.is_rms_norm
)
dx0 = dx0mat.view(-1, *x.shape[1:])
dresidual = dresidualmat.view(x.shape) if dresidualmat is not None else None
dcolscale = rest[0] if colscale is not None else None
return (dx0, dresidual, dgamma, dbeta if ctx.has_beta else None, dcolscale, None, None,
None, None, None, None, None, None, None, None)
class DropoutAddLayerNormParallelResidualFn(torch.autograd.Function):
@staticmethod
def forward(ctx, x0, x1, residual, gamma0, beta0, gamma1, beta1, dropout_p, epsilon,
residual_in_fp32=False, prenorm=False, is_rms_norm=False, return_dmask=False):
x0 = maybe_align(x0.contiguous(), 16)
x1 = maybe_align(x1.contiguous(), 16) if x1 is not None else None
residual = maybe_align(residual.contiguous(), 16) if residual is not None else None
gamma0 = maybe_align(gamma0.contiguous(), 16)
beta0 = maybe_align(beta0.contiguous(), 16) if beta0 is not None else None
gamma1 = maybe_align(gamma1.contiguous(), 16) if gamma1 is not None else None
beta1 = maybe_align(beta1.contiguous(), 16) if beta1 is not None else None
z0mat, z1mat, xmat, dmask0, dmask1, mu, rsigma = _dropout_add_layer_norm_parallel_residual_forward(
x0, x1, residual, gamma0, beta0, gamma1, beta1, dropout_p, epsilon,
residual_in_fp32, is_rms_norm
)
ctx.save_for_backward(xmat.view(x0.shape), dmask0, dmask1, gamma0, gamma1, mu, rsigma)
ctx.prenorm = prenorm
ctx.dropout_p = dropout_p
ctx.has_x1 = x1 is not None
ctx.has_residual = residual is not None
ctx.is_rms_norm = is_rms_norm
ctx.has_beta = beta0 is not None
z = (z0mat.view(x0.shape), z1mat.view(x0.shape) if z1mat is not None else None)
if not return_dmask:
return z if not prenorm else (*z, xmat.view(x0.shape))
else:
dmask0 = (dmask0.view(x0.shape) if dropout_p > 0.
else torch.ones(x0.shape, dtype=torch.uint8, device=x0.device))
dmask1 = (dmask1.view(x0.shape) if dropout_p > 0. and x1 is not None
else torch.ones(x0.shape, dtype=torch.uint8, device=x0.device))
ctx.mark_non_differentiable(dmask0)
ctx.mark_non_differentiable(dmask1)
return (*z, dmask0, dmask1) if not prenorm else (*z, xmat.view(x0.shape), dmask0, dmask1)
@staticmethod
def backward(ctx, dz0, dz1, *args):
dz0 = maybe_align(dz0.contiguous(), 16) # this happens!
dz1 = maybe_align(dz1.contiguous(), 16) if dz1 is not None else None
dx = maybe_align(args[0].contiguous(), 16) if ctx.prenorm else None
x, dmask0, dmask1, gamma0, gamma1, mu, rsigma = ctx.saved_tensors
dropout_p = ctx.dropout_p
has_x1 = ctx.has_x1
has_residual = ctx.has_residual
dx0mat, dx1mat, dresidualmat, dgamma0, dbeta0, dgamma1, dbeta1 = _dropout_add_layer_norm_parallel_residual_backward(
dz0, dz1, dx, x, dmask0, dmask1, mu, rsigma, gamma0, gamma1, dropout_p, has_x1,
has_residual, ctx.is_rms_norm
)
dx0 = dx0mat.view(x.shape)
dx1 = dx1mat.view(x.shape) if dx1mat is not None else None
dresidual = dresidualmat.view(x.shape) if dresidualmat is not None else None
return (dx0, dx1, dresidual, dgamma0, dbeta0 if ctx.has_beta else None, dgamma1,
dbeta1 if ctx.has_beta else None, None, None, None, None, None, None)
def layer_norm(x, weight, bias, epsilon):
return DropoutAddLayerNormFn.apply(x, None, weight, bias, None, None, 0.0, epsilon, False)
def dropout_add_layer_norm(x0, residual, weight, bias, dropout_p, epsilon, rowscale=None,
layerscale=None, prenorm=False, residual_in_fp32=False,
return_dropout_mask=False):
"""residual_in_fp32 only has an effect if residual is None.
Otherwise residual dtype is residual.dtype.
"""
return DropoutAddLayerNormFn.apply(
x0, residual, weight, bias, rowscale, layerscale, dropout_p, epsilon, residual_in_fp32, prenorm,
False, return_dropout_mask
)
def dropout_add_layer_norm_subset(x0, residual, weight, bias, dropout_p, epsilon, layerscale=None,
x0_subset=None, out_subset=None, rowscale_const=1.0,
out_numrows=0, prenorm=False, residual_in_fp32=False,
return_dropout_mask=False):
"""residual_in_fp32 only has an effect if residual is None.
Otherwise residual dtype is residual.dtype.
"""
return DropoutAddLayerNormSubsetFn.apply(
x0, residual, weight, bias, layerscale, x0_subset, out_subset, dropout_p, epsilon,
rowscale_const, out_numrows, residual_in_fp32, prenorm, False, return_dropout_mask
)
def dropout_add_layer_norm_parallel_residual(
x0, x1, residual, weight0, bias0, weight1, bias1, dropout_p, epsilon, prenorm=False,
residual_in_fp32=False, return_dropout_mask=False
):
"""residual_in_fp32 only has an effect if residual is None.
Otherwise residual dtype is residual.dtype.
"""
return DropoutAddLayerNormParallelResidualFn.apply(
x0, x1, residual, weight0, bias0, weight1, bias1, dropout_p, epsilon, residual_in_fp32, prenorm,
False, return_dropout_mask
)
class DropoutAddLayerNorm(torch.nn.Module):
def __init__(self, hidden_size, prenorm=False, p=0.0, eps=1e-5, residual_in_fp32=False,
device=None, dtype=None):
factory_kwargs = {'device': device, 'dtype': dtype}
super().__init__()
self.prenorm = prenorm
self.p = p
self.eps = eps
self.residual_in_fp32 = residual_in_fp32
self.weight = torch.nn.Parameter(torch.empty(hidden_size, **factory_kwargs))
self.bias = torch.nn.Parameter(torch.empty(hidden_size, **factory_kwargs))
self.reset_parameters()
def reset_parameters(self):
init.ones_(self.weight)
init.zeros_(self.bias)
def forward(self, x0, residual=None):
return dropout_add_layer_norm(x0, residual, self.weight, self.bias,
self.p if self.training else 0.0, self.eps,
prenorm=self.prenorm, residual_in_fp32=self.residual_in_fp32)