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import torch
import torch.nn as nn
from torch.utils._pytree import tree_map, tree_flatten, tree_unflatten
from typing import List, Any, Dict, Optional, Union, NamedTuple
from collections import defaultdict
from torch.utils._python_dispatch import TorchDispatchMode
from torch.utils.hooks import RemovableHandle
from torch._decomp import register_decomposition
from math import prod
from functools import wraps
__all__ = ["FlopCounterMode", "register_flop_formula"]
aten = torch.ops.aten
def get_shape(i):
if isinstance(i, torch.Tensor):
return i.shape
return i
flop_registry: Dict[Any, Any] = {}
def shape_wrapper(f):
@wraps(f)
def nf(*args, out=None, **kwargs):
args, kwargs, out_shape = tree_map(get_shape, (args, kwargs, out))
return f(*args, out_shape=out_shape, **kwargs)
return nf
def register_flop_formula(targets, get_raw=False):
def register_fun(flop_formula):
if not get_raw:
flop_formula = shape_wrapper(flop_formula)
register_decomposition(targets, registry=flop_registry, unsafe=True)(flop_formula)
return flop_formula
return register_fun
@register_flop_formula(aten.mm)
def mm_flop(a_shape, b_shape, *args, out_shape=None, **kwargs) -> int:
"""Count flops for matmul."""
# Inputs should be a list of length 2.
# Inputs contains the shapes of two matrices.
m, k = a_shape
k2, n = b_shape
assert k == k2
# NB(chilli): Should be 2 * k - 1 technically for FLOPs.
return m * n * 2 * k
@register_flop_formula(aten.addmm)
def addmm_flop(self_shape, a_shape, b_shape, out_shape=None, **kwargs) -> int:
"""Count flops for addmm."""
return mm_flop(a_shape, b_shape)
@register_flop_formula(aten.bmm)
def bmm_flop(a_shape, b_shape, out_shape=None, **kwargs) -> int:
"""Count flops for the bmm operation."""
# Inputs should be a list of length 2.
# Inputs contains the shapes of two tensor.
b, m, k = a_shape
b2, k2, n = b_shape
assert b == b2
assert k == k2
# NB(chilli): Should be 2 * k - 1 technically for FLOPs.
flop = b * m * n * 2 * k
return flop
@register_flop_formula(aten.baddbmm)
def baddbmm_flop(self_shape, a_shape, b_shape, out_shape=None, **kwargs) -> int:
"""Count flops for the baddbmm operation."""
# Inputs should be a list of length 3.
# Inputs contains the shapes of three tensors.
return bmm_flop(a_shape, b_shape)
def conv_flop_count(
x_shape: List[int],
w_shape: List[int],
out_shape: List[int],
transposed: bool = False,
) -> int:
"""Count flops for convolution.
Note only multiplication is
counted. Computation for bias are ignored.
Flops for a transposed convolution are calculated as
flops = (x_shape[2:] * prod(w_shape) * batch_size).
Args:
x_shape (list(int)): The input shape before convolution.
w_shape (list(int)): The filter shape.
out_shape (list(int)): The output shape after convolution.
transposed (bool): is the convolution transposed
Returns:
int: the number of flops
"""
batch_size = x_shape[0]
conv_shape = (x_shape if transposed else out_shape)[2:]
c_out, c_in, *filter_size = w_shape
"""
General idea here is that for a regular conv, for each point in the output
spatial dimension we convolve the filter with something (hence
`prod(conv_shape) * prod(filter_size)` ops). Then, this gets multiplied by
1. batch_size, 2. the cross product of input and weight channels.
For the transpose, it's not each point in the *output* spatial dimension but
each point in the *input* spatial dimension.
"""
# NB(chilli): I don't think this properly accounts for padding :think:
# NB(chilli): Should be 2 * c_in - 1 technically for FLOPs.
flop = prod(conv_shape) * prod(filter_size) * batch_size * c_out * c_in * 2
return flop
@register_flop_formula([aten.convolution, aten._convolution])
def conv_flop(x_shape, w_shape, _bias, _stride, _padding, _dilation, transposed, *args, out_shape=None, **kwargs) -> int:
"""Count flops for convolution."""
return conv_flop_count(x_shape, w_shape, out_shape, transposed=transposed)
@register_flop_formula(aten.convolution_backward)
def conv_backward_flop(
grad_out_shape,
x_shape,
w_shape,
_bias,
_stride,
_padding,
_dilation,
transposed,
_output_padding,
_groups,
output_mask,
out_shape) -> int:
def t(shape):
return [shape[1], shape[0]] + list(shape[2:])
flop_count = 0
"""
Let's say we have a regular 1D conv
{A, B, C} [inp]
{i, j} [weight]
=> (conv)
{Ai + Bj, Bi + Cj} [out]
And as a reminder, the transposed conv of the above is
=> {Ai, Aj + Bi, Bj + Ci, Cj} [transposed conv out]
For the backwards of conv, we now have
{D, E} [grad_out]
{A, B, C} [inp]
{i, j} [weight]
# grad_inp as conv_transpose(grad_out, weight)
Let's first compute grad_inp. To do so, we can simply look at all the
multiplications that each element of inp is involved in. For example, A is
only involved in the first element of the output (and thus only depends upon
D in grad_out), and C is only involved in the last element of the output
(and thus only depends upon E in grad_out)
{Di, Dj + Ei, Ej} [grad_inp]
Note that this corresponds to the below conv_transpose. This gives us the
output_mask[0] branch, which is grad_inp.
{D, E} [inp (grad_out)]
{i, j} [weight]
=> (conv_transpose)
{Di, Dj + Ei, Ej} [out (grad_inp)]
I leave the fact that grad_inp for a transposed conv is just conv(grad_out,
weight) as an exercise for the reader.
# grad_weight as conv(inp, grad_out)
To compute grad_weight, we again look at the terms in the output, which as
a reminder is:
=> {Ai + Bj, Bi + Cj} [out]
=> {D, E} [grad_out]
If we manually compute the gradient for the weights, we see it's
{AD + BE, BD + CE} [grad_weight]
This corresponds to the below conv
{A, B, C} [inp]
{D, E} [weight (grad_out)]
=> (conv)
{AD + BE, BD + CE} [out (grad_weight)]
# grad_weight of transposed conv as conv(grad_out, inp)
As a reminder, the terms of the output of a transposed conv are:
=> {Ai, Aj + Bi, Bj + Ci, Cj} [transposed conv out]
=> {D, E, F, G} [grad_out]
Manually computing the gradient for the weights, we see it's
{AD + BE + CF, AE + BF + CG} [grad_weight]
This corresponds to the below conv
{D, E, F, G} [inp (grad_out)]
{A, B, C} [weight (inp)]
=> (conv)
{AD + BE + CF, AE + BF + CG} [out (grad_weight)]
For the full backwards formula, there are also some details involving
transpose of the batch/channel dimensions and groups, but I skip those for
the sake of brevity (and they're pretty similar to matmul backwards)
Check [conv backwards decomposition as conv forwards]
"""
# grad_inp as conv_transpose(grad_out, weight)
if output_mask[0]:
grad_input_shape = get_shape(out_shape[0])
flop_count += conv_flop_count(grad_out_shape, w_shape, grad_input_shape, not transposed)
if output_mask[1]:
grad_weight_shape = get_shape(out_shape[1])
if transposed:
# grad_weight of transposed conv as conv(grad_out, inp)
flop_count += conv_flop_count(t(grad_out_shape), t(x_shape), t(grad_weight_shape), transposed=False)
else:
# grad_weight as conv(inp, grad_out)
flop_count += conv_flop_count(t(x_shape), t(grad_out_shape), t(grad_weight_shape), transposed=False)
return flop_count
def sdpa_flop_count(query_shape, key_shape, value_shape):
"""
Count flops for self-attention.
NB: We can assume that value_shape == key_shape
"""
b, h, s_q, d_q = query_shape
_b2, _h2, s_k, _d2 = key_shape
_b3, _h3, _s3, d_v = value_shape
assert b == _b2 == _b3 and h == _h2 == _h3 and d_q == _d2 and s_k == _s3 and d_q == _d2
total_flops = 0
# q: [b, h, s_q, d_q] @ k: [b, h, d_q, s_k] -> scores: [b, h, s_q, s_k]
total_flops += bmm_flop((b * h, s_q, d_q), (b * h, d_q, s_k))
# scores: [b, h, s_q, s_k] @ v: [b, h, s_k, d_v] -> out: [b, h, s_q, d_v]
total_flops += bmm_flop((b * h, s_q, s_k), (b * h, s_k, d_v))
return total_flops
@register_flop_formula([aten._scaled_dot_product_efficient_attention, aten._scaled_dot_product_flash_attention])
def sdpa_flop(query_shape, key_shape, value_shape, *args, out_shape=None, **kwargs) -> int:
"""Count flops for self-attention."""
# NB: We aren't accounting for causal attention here
return sdpa_flop_count(query_shape, key_shape, value_shape)
def sdpa_backward_flop_count(grad_out_shape, query_shape, key_shape, value_shape):
total_flops = 0
b, h, s_q, d_q = query_shape
_b2, _h2, s_k, _d2 = key_shape
_b3, _h3, _s3, d_v = value_shape
_b4, _h4, _s4, _d4 = grad_out_shape
assert b == _b2 == _b3 == _b4 and h == _h2 == _h3 == _h4 and d_q == _d2
assert d_v == _d4 and s_k == _s3 and s_q == _s4
total_flops = 0
# Step 1: We recompute the scores matrix.
# q: [b, h, s_q, d_q] @ k: [b, h, d_q, s_k] -> scores: [b, h, s_q, s_k]
total_flops += bmm_flop((b * h, s_q, d_q), (b * h, d_q, s_k))
# Step 2: We propagate the gradients through the score @ v operation.
# gradOut: [b, h, s_q, d_v] @ v: [b, h, d_v, s_k] -> gradScores: [b, h, s_q, s_k]
total_flops += bmm_flop((b * h, s_q, d_v), (b * h, d_v, s_k))
# scores: [b, h, s_k, s_q] @ gradOut: [b, h, s_q, d_v] -> gradV: [b, h, s_k, d_v]
total_flops += bmm_flop((b * h, s_k, s_q), (b * h, s_q, d_v))
# Step 3: We propagate th gradients through the k @ v operation
# gradScores: [b, h, s_q, s_k] @ k: [b, h, s_k, d_q] -> gradQ: [b, h, s_q, d_q]
total_flops += bmm_flop((b * h, s_q, s_k), (b * h, s_k, d_q))
# q: [b, h, d_q, s_q] @ gradScores: [b, h, s_q, s_k] -> gradK: [b, h, d_q, s_k]
total_flops += bmm_flop((b * h, d_q, s_q), (b * h, s_q, s_k))
return total_flops
@register_flop_formula([aten._scaled_dot_product_efficient_attention_backward, aten._scaled_dot_product_flash_attention_backward])
def sdpa_backward_flop(grad_out_shape, query_shape, key_shape, value_shape, *args, out_shape=None, **kwargs) -> int:
"""Count flops for self-attention backward."""
return sdpa_backward_flop_count(grad_out_shape, query_shape, key_shape, value_shape)
flop_registry = {
aten.mm: mm_flop,
aten.addmm: addmm_flop,
aten.bmm: bmm_flop,
aten.baddbmm: baddbmm_flop,
aten.convolution: conv_flop,
aten._convolution: conv_flop,
aten.convolution_backward: conv_backward_flop,
aten._scaled_dot_product_efficient_attention: sdpa_flop,
aten._scaled_dot_product_flash_attention: sdpa_flop,
aten._scaled_dot_product_efficient_attention_backward: sdpa_backward_flop,
aten._scaled_dot_product_flash_attention_backward: sdpa_backward_flop,
}
def normalize_tuple(x):
if not isinstance(x, tuple):
return (x,)
return x
# Define the suffixes for different orders of magnitude
suffixes = ["", "K", "M", "B", "T"]
# Thanks BingChat!
def get_suffix_str(number):
# Find the index of the appropriate suffix based on the number of digits
# with some additional overflow.
# i.e. 1.01B should be displayed as 1001M, not 1.001B
index = max(0, min(len(suffixes) - 1, (len(str(number)) - 2) // 3))
return suffixes[index]
def convert_num_with_suffix(number, suffix):
index = suffixes.index(suffix)
# Divide the number by 1000^index and format it to two decimal places
value = f"{number / 1000 ** index:.3f}"
# Return the value and the suffix as a string
return value + suffixes[index]
def convert_to_percent_str(num, denom):
if denom == 0:
return "0%"
return f"{num / denom:.2%}"
def _pytreeify_preserve_structure(f):
@wraps(f)
def nf(args):
flat_args, spec = tree_flatten(args)
out = f(*flat_args)
return tree_unflatten(out, spec)
return nf
class FlopCounterMode(TorchDispatchMode):
"""
``FlopCounterMode`` is a context manager that counts the number of flops within its context.
It does this using a ``TorchDispatchMode``.
It also supports hierarchical output by passing a module (or list of
modules) to FlopCounterMode on construction. If you do not need hierarchical
output, you do not need to use it with a module.
Example usage
.. code-block:: python
mod = ...
flop_counter = FlopCounterMode(mod)
with flop_counter:
mod.sum().backward()
"""
def __init__(
self,
mods: Optional[Union[torch.nn.Module, List[torch.nn.Module]]] = None,
depth: int = 2,
display: bool = True,
custom_mapping: Optional[Dict[Any, Any]] = None):
self.flop_counts: Dict[str, Dict[Any, int]] = defaultdict(lambda: defaultdict(int))
self.depth = depth
self.parents = ["Global"]
self.in_backward = False
self.display = display
if custom_mapping is None:
custom_mapping = {}
if isinstance(mods, torch.nn.Module):
mods = [mods]
self.mods = mods
# Keys will include the modules in `mods` and their submodules
self._module_to_forward_hook_handles: Dict[nn.Module, _ForwardHookHandles] = {}
self.flop_registry = {
**flop_registry,
**{k: v if getattr(v, "_get_raw", False) else shape_wrapper(v) for k, v in custom_mapping.items()}
}
def _register_forward_hooks(self):
if self.mods is None:
return
for mod in self.mods:
prefix = type(mod).__name__
for name, module in dict(mod.named_modules()).items():
if name == "":
name = prefix
else:
name = ".".join([prefix, name])
forward_pre_hook_handle = module.register_forward_pre_hook(self._enter_module(name))
forward_hook_handle = module.register_forward_hook(self._exit_module(name))
self._module_to_forward_hook_handles[module] = _ForwardHookHandles(
forward_pre_hook_handle, forward_hook_handle
)
def _deregister_forward_hooks(self):
for forward_hook_handles in self._module_to_forward_hook_handles.values():
forward_hook_handles[0].remove()
forward_hook_handles[1].remove()
self._module_to_forward_hook_handles.clear()
def _enter_module(self, name):
def f(module, inputs):
out = _pytreeify_preserve_structure(self._create_pre_module(name))(inputs)
return out
return f
def _exit_module(self, name):
def f(module, inputs, outputs):
outputs = _pytreeify_preserve_structure(self._create_post_module(name))(outputs)
return outputs
return f
def _create_post_module(self, name):
class PushState(torch.autograd.Function):
@staticmethod
def forward(ctx, *args):
assert self.parents[-1] == name, f"{self.parents[-1]} is not {name}"
self.parents.pop()
args = tree_map(lambda x: x.clone() if isinstance(x, torch.Tensor) else x, args)
return args
@staticmethod
def backward(ctx, *grad_outs):
self.in_backward = True
self.parents.append(name)
return grad_outs
return PushState.apply
def _create_pre_module(self, name):
class PopState(torch.autograd.Function):
@staticmethod
def forward(ctx, *args):
if self.in_backward:
self.parents = ["Global"]
self.in_backward = True
self.parents.append(name)
args = tree_map(lambda x: x.clone() if isinstance(x, torch.Tensor) else x, args)
return args
@staticmethod
def backward(ctx, *grad_outs):
assert self.parents[-1] == name
self.parents.pop()
return grad_outs
return PopState.apply
def get_total_flops(self) -> int:
return sum(self.flop_counts['Global'].values())
def get_flop_counts(self) -> Dict[str, Dict[Any, int]]:
"""Return the flop counts as a dictionary of dictionaries.
The outer
dictionary is keyed by module name, and the inner dictionary is keyed by
operation name.
Returns:
Dict[str, Dict[Any, int]]: The flop counts as a dictionary.
"""
return {k: dict(v) for k, v in self.flop_counts.items()}
def get_table(self, depth=None):
if depth is None:
depth = self.depth
if depth is None:
depth = 999999
import tabulate
tabulate.PRESERVE_WHITESPACE = True
header = ["Module", "FLOP", "% Total"]
values = []
global_flops = self.get_total_flops()
global_suffix = get_suffix_str(global_flops)
is_global_subsumed = False
def process_mod(mod_name, depth):
nonlocal is_global_subsumed
total_flops = sum(self.flop_counts[mod_name].values())
is_global_subsumed |= total_flops >= global_flops
padding = " " * depth
values = []
values.append([
padding + mod_name,
convert_num_with_suffix(total_flops, global_suffix),
convert_to_percent_str(total_flops, global_flops)
])
for k, v in self.flop_counts[mod_name].items():
values.append([
padding + " - " + str(k),
convert_num_with_suffix(v, global_suffix),
convert_to_percent_str(v, global_flops)
])
return values
for mod in self.flop_counts.keys():
if mod == 'Global':
continue
mod_depth = mod.count(".") + 1
if mod_depth > depth:
continue
cur_values = process_mod(mod, mod_depth - 1)
values.extend(cur_values)
# We do a bit of messing around here to only output the "Global" value
# if there are any FLOPs in there that aren't already fully contained by
# a module.
if 'Global' in self.flop_counts and not is_global_subsumed:
for idx, value in enumerate(values):
values[idx][0] = " " + values[idx][0]
values = process_mod('Global', 0) + values
if len(values) == 0:
values = [["Global", "0", "0%"]]
return tabulate.tabulate(values, headers=header, colalign=("left", "right", "right"))
def __enter__(self):
self.flop_counts.clear()
self._register_forward_hooks()
super().__enter__()
return self
def __exit__(self, *args):
if self.display:
print(self.get_table(self.depth))
self._deregister_forward_hooks()
super().__exit__(*args)
def __torch_dispatch__(self, func, types, args=(), kwargs=None):
kwargs = kwargs if kwargs else {}
out = func(*args, **kwargs)
func_packet = func._overloadpacket
if func_packet in self.flop_registry:
flop_count_func = self.flop_registry[func_packet]
flop_count = flop_count_func(*args, **kwargs, out=out) # type: ignore[operator]
if len(set(self.parents)) != len(self.parents):
print(
"The module hierarchy tracking seems to be messed up."
"Please file a bug or just run the flop counter without"
"tracking the module hierarchy (i.e. `with FlopCounterMode():`)"
)
for par in set(self.parents):
self.flop_counts[par][func_packet] += flop_count
return out
class _ForwardHookHandles(NamedTuple):
forward_pre_hook_handle: RemovableHandle
forward_hook_handle: RemovableHandle