'How to reduce model size in Pytorch post training
I have created a pytorch model and I want to reduce the model size. Defining Model Architecture :-
import torch
import torch.quantization
import torch.nn as nn
import copy
import os
import time
import numpy as np
import torch.autograd as autograd
from torch.autograd import Variable
import torch.nn.utils.prune as prune
import torch.nn.functional as F
import os
import random
import numpy as np
import pandas as pd
import matplotlib.pyplot as plt
import sys
import time
import codecs
import pickle
import torch
from torch.autograd import Variable
import torch.nn.utils.prune as prune
from config import Config
from loader import *
from utils import *
from model import BiLSTM_CRF
START_TAG = '<START>'
STOP_TAG = '<STOP>'
def init_embedding(input_embedding):
"""
Initialize embedding
"""
bias = np.sqrt(3.0 / input_embedding.size(1))
nn.init.uniform(input_embedding, -bias, bias)
def init_linear(input_linear):
"""
Initialize linear transformation
"""
bias = np.sqrt(6.0 / (input_linear.weight.size(0) + input_linear.weight.size(1)))
nn.init.uniform(input_linear.weight, -bias, bias)
if input_linear.bias is not None:
input_linear.bias.data.zero_()
def init_lstm(input_lstm):
"""
Initialize lstm
"""
for ind in range(0, input_lstm.num_layers):
weight = eval('input_lstm.weight_ih_l' + str(ind))
bias = np.sqrt(6.0 / (weight.size(0) / 4 + weight.size(1)))
nn.init.uniform(weight, -bias, bias)
weight = eval('input_lstm.weight_hh_l' + str(ind))
bias = np.sqrt(6.0 / (weight.size(0) / 4 + weight.size(1)))
nn.init.uniform(weight, -bias, bias)
if input_lstm.bidirectional:
for ind in range(0, input_lstm.num_layers):
weight = eval('input_lstm.weight_ih_l' + str(ind) + '_reverse')
bias = np.sqrt(6.0 / (weight.size(0) / 4 + weight.size(1)))
nn.init.uniform(weight, -bias, bias)
weight = eval('input_lstm.weight_hh_l' + str(ind) + '_reverse')
bias = np.sqrt(6.0 / (weight.size(0) / 4 + weight.size(1)))
nn.init.uniform(weight, -bias, bias)
if input_lstm.bias:
for ind in range(0, input_lstm.num_layers):
weight = eval('input_lstm.bias_ih_l' + str(ind))
weight.data.zero_()
weight.data[input_lstm.hidden_size: 2 * input_lstm.hidden_size] = 1
weight = eval('input_lstm.bias_hh_l' + str(ind))
weight.data.zero_()
weight.data[input_lstm.hidden_size: 2 * input_lstm.hidden_size] = 1
if input_lstm.bidirectional:
for ind in range(0, input_lstm.num_layers):
weight = eval('input_lstm.bias_ih_l' + str(ind) + '_reverse')
weight.data.zero_()
weight.data[input_lstm.hidden_size: 2 * input_lstm.hidden_size] = 1
weight = eval('input_lstm.bias_hh_l' + str(ind) + '_reverse')
weight.data.zero_()
weight.data[input_lstm.hidden_size: 2 * input_lstm.hidden_size] = 1
def to_scalar(var):
return var.view(-1).data.tolist()[0]
def argmax(vec):
_, idx = torch.max(vec, 1)
return to_scalar(idx)
def log_sum_exp(vec):
# vec 2D: 1 * tagset_size
max_score = vec[0, argmax(vec)]
max_score_broadcast = max_score.view(1, -1).expand(1, vec.size()[1])
return max_score + \
torch.log(torch.sum(torch.exp(vec - max_score_broadcast)))
class BiLSTM_CRF(nn.Module):
def __init__(self, vocab_size, tag_to_ix, embedding_dim, hidden_dim, char_lstm_dim=25,
char_to_ix=None, pre_word_embeds=None, char_embedding_dim=25, use_gpu=False,
n_cap=None, cap_embedding_dim=None, use_crf=True, char_mode='CNN'):
super(BiLSTM_CRF, self).__init__()
self.use_gpu = use_gpu
self.embedding_dim = embedding_dim #100
self.hidden_dim = hidden_dim #200
self.vocab_size = vocab_size
self.tag_to_ix = tag_to_ix
self.n_cap = n_cap
self.cap_embedding_dim = cap_embedding_dim
self.use_crf = use_crf
self.tagset_size = len(tag_to_ix)
self.out_channels = char_lstm_dim #25
self.char_mode = char_mode
print('char_mode: %s, out_channels: %d, hidden_dim: %d, ' % (char_mode, char_lstm_dim, hidden_dim))
if self.n_cap and self.cap_embedding_dim:
self.cap_embeds = nn.Embedding(self.n_cap, self.cap_embedding_dim)
# print("self.cap_embeds.weight------",self.cap_embeds.weight)
init_embedding(self.cap_embeds.weight)
if char_embedding_dim is not None:
self.char_lstm_dim = char_lstm_dim
self.char_embeds = nn.Embedding(len(char_to_ix), char_embedding_dim)
# print("self.char_embeds.weight-------", self.char_embeds.weight)
init_embedding(self.char_embeds.weight)
if self.char_mode == 'LSTM':
self.char_lstm = nn.LSTM(char_embedding_dim, char_lstm_dim, num_layers=1, bidirectional=True)
init_lstm(self.char_lstm)
if self.char_mode == 'CNN':
self.char_cnn3 = nn.Conv2d(in_channels=1, out_channels=self.out_channels, kernel_size=(3, char_embedding_dim), padding=(2,0))
self.word_embeds = nn.Embedding(vocab_size, embedding_dim)
if pre_word_embeds is not None:
self.pre_word_embeds = True
self.word_embeds.weight = nn.Parameter(torch.FloatTensor(pre_word_embeds))
else:
self.pre_word_embeds = False
self.dropout = nn.Dropout(0.5)
if self.n_cap and self.cap_embedding_dim:
if self.char_mode == 'LSTM':
self.lstm = nn.LSTM(embedding_dim+char_lstm_dim*2+cap_embedding_dim, hidden_dim, bidirectional=True)
if self.char_mode == 'CNN':
self.lstm = nn.LSTM(embedding_dim+self.out_channels+cap_embedding_dim, hidden_dim, bidirectional=True)
else:
if self.char_mode == 'LSTM':
self.lstm = nn.LSTM(embedding_dim+char_lstm_dim*2, hidden_dim, bidirectional=True)
if self.char_mode == 'CNN':
self.lstm = nn.LSTM(embedding_dim+self.out_channels, hidden_dim, bidirectional=True)
init_lstm(self.lstm)
self.hw_trans = nn.Linear(self.out_channels, self.out_channels)
self.hw_gate = nn.Linear(self.out_channels, self.out_channels)
self.h2_h1 = nn.Linear(hidden_dim*2, hidden_dim)
self.tanh = nn.Tanh()
self.hidden2tag = nn.Linear(hidden_dim*2, self.tagset_size)
init_linear(self.h2_h1)
init_linear(self.hidden2tag)
init_linear(self.hw_gate)
init_linear(self.hw_trans)
if self.use_crf:
self.transitions = nn.Parameter(
torch.zeros(self.tagset_size, self.tagset_size))
self.transitions.data[tag_to_ix[START_TAG], :] = -10000
self.transitions.data[:, tag_to_ix[STOP_TAG]] = -10000
def _score_sentence(self, feats, tags):
# tags is ground_truth, a list of ints, length is len(sentence)
# feats is a 2D tensor, len(sentence) * tagset_size
r = torch.LongTensor(range(feats.size()[0]))
if self.use_gpu:
r = r.cuda()
pad_start_tags = torch.cat([torch.cuda.LongTensor([self.tag_to_ix[START_TAG]]), tags])
pad_stop_tags = torch.cat([tags, torch.cuda.LongTensor([self.tag_to_ix[STOP_TAG]])])
else:
pad_start_tags = torch.cat([torch.LongTensor([self.tag_to_ix[START_TAG]]), tags])
pad_stop_tags = torch.cat([tags, torch.LongTensor([self.tag_to_ix[STOP_TAG]])])
score = torch.sum(self.transitions[pad_stop_tags, pad_start_tags]) + torch.sum(feats[r, tags])
return score
def _get_lstm_features(self, sentence, chars2, caps, chars2_length, d):
if self.char_mode == 'LSTM':
# self.char_lstm_hidden = self.init_lstm_hidden(dim=self.char_lstm_dim, bidirection=True, batchsize=chars2.size(0))
chars_embeds = self.char_embeds(chars2).transpose(0, 1)
packed = torch.nn.utils.rnn.pack_padded_sequence(chars_embeds, chars2_length)
lstm_out, _ = self.char_lstm(packed)
outputs, output_lengths = torch.nn.utils.rnn.pad_packed_sequence(lstm_out)
outputs = outputs.transpose(0, 1)
chars_embeds_temp = Variable(torch.FloatTensor(torch.zeros((outputs.size(0), outputs.size(2)))))
if self.use_gpu:
chars_embeds_temp = chars_embeds_temp.cuda()
for i, index in enumerate(output_lengths):
chars_embeds_temp[i] = torch.cat((outputs[i, index-1, :self.char_lstm_dim], outputs[i, 0, self.char_lstm_dim:]))
chars_embeds = chars_embeds_temp.clone()
for i in range(chars_embeds.size(0)):
chars_embeds[d[i]] = chars_embeds_temp[i]
if self.char_mode == 'CNN':
chars_embeds = self.char_embeds(chars2).unsqueeze(1)
chars_cnn_out3 = self.char_cnn3(chars_embeds)
chars_embeds = nn.functional.max_pool2d(chars_cnn_out3, kernel_size=(chars_cnn_out3.size(2), 1)).view(chars_cnn_out3.size(0), self.out_channels)
# t = self.hw_gate(chars_embeds)
# g = nn.functional.sigmoid(t)
# h = nn.functional.relu(self.hw_trans(chars_embeds))
# chars_embeds = g * h + (1 - g) * chars_embeds
embeds = self.word_embeds(sentence)
if self.n_cap and self.cap_embedding_dim:
cap_embedding = self.cap_embeds(caps)
if self.n_cap and self.cap_embedding_dim:
embeds = torch.cat((embeds, chars_embeds, cap_embedding), 1)
else:
embeds = torch.cat((embeds, chars_embeds), 1)
embeds = embeds.unsqueeze(1)
embeds = self.dropout(embeds)
lstm_out, _ = self.lstm(embeds)
lstm_out = lstm_out.view(len(sentence), self.hidden_dim*2)
lstm_out = self.dropout(lstm_out)
lstm_feats = self.hidden2tag(lstm_out)
return lstm_feats
def _forward_alg(self, feats):
# calculate in log domain
# feats is len(sentence) * tagset_size
# initialize alpha with a Tensor with values all equal to -10000.
init_alphas = torch.Tensor(1, self.tagset_size).fill_(-10000.)
init_alphas[0][self.tag_to_ix[START_TAG]] = 0.
forward_var = autograd.Variable(init_alphas)
if self.use_gpu:
forward_var = forward_var.cuda()
for feat in feats:
emit_score = feat.view(-1, 1)
tag_var = forward_var + self.transitions + emit_score
max_tag_var, _ = torch.max(tag_var, dim=1)
tag_var = tag_var - max_tag_var.view(-1, 1)
forward_var = max_tag_var + torch.log(torch.sum(torch.exp(tag_var), dim=1)).view(1, -1) # ).view(1, -1)
terminal_var = (forward_var + self.transitions[self.tag_to_ix[STOP_TAG]]).view(1, -1)
alpha = log_sum_exp(terminal_var)
# Z(x)
return alpha
def viterbi_decode(self, feats):
backpointers = []
# analogous to forward
init_vvars = torch.Tensor(1, self.tagset_size).fill_(-10000.)
init_vvars[0][self.tag_to_ix[START_TAG]] = 0
forward_var = Variable(init_vvars)
if self.use_gpu:
forward_var = forward_var.cuda()
for feat in feats:
next_tag_var = forward_var.view(1, -1).expand(self.tagset_size, self.tagset_size) + self.transitions
_, bptrs_t = torch.max(next_tag_var, dim=1)
bptrs_t = bptrs_t.squeeze().data.cpu().numpy()
next_tag_var = next_tag_var.data.cpu().numpy()
viterbivars_t = next_tag_var[range(len(bptrs_t)), bptrs_t]
viterbivars_t = Variable(torch.FloatTensor(viterbivars_t))
if self.use_gpu:
viterbivars_t = viterbivars_t.cuda()
forward_var = viterbivars_t + feat
backpointers.append(bptrs_t)
terminal_var = forward_var + self.transitions[self.tag_to_ix[STOP_TAG]]
terminal_var.data[self.tag_to_ix[STOP_TAG]] = -10000.
terminal_var.data[self.tag_to_ix[START_TAG]] = -10000.
best_tag_id = argmax(terminal_var.unsqueeze(0))
path_score = terminal_var[best_tag_id]
best_path = [best_tag_id]
for bptrs_t in reversed(backpointers):
best_tag_id = bptrs_t[best_tag_id]
best_path.append(best_tag_id)
start = best_path.pop()
assert start == self.tag_to_ix[START_TAG]
best_path.reverse()
return path_score, best_path
def neg_log_likelihood(self, sentence, tags, chars2, caps, chars2_length, d):
# sentence, tags is a list of ints
# features is a 2D tensor, len(sentence) * self.tagset_size
feats = self._get_lstm_features(sentence, chars2, caps, chars2_length, d)
if self.use_crf:
forward_score = self._forward_alg(feats)
gold_score = self._score_sentence(feats, tags)
return forward_score - gold_score
else:
tags = Variable(tags)
scores = nn.functional.cross_entropy(feats, tags)
return scores
def forward(self, sentence, chars, caps, chars2_length, d):
feats = self._get_lstm_features(sentence, chars, caps, chars2_length, d)
# viterbi to get tag_seq
if self.use_crf:
score, tag_seq = self.viterbi_decode(feats)
else:
score, tag_seq = torch.max(feats, 1)
tag_seq = list(tag_seq.cpu().data)
return score, tag_seq
create Model Instance:-
model_fp32 = BiLSTM_CRF(vocab_size=len(word_to_id),
tag_to_ix=tag_to_id,
embedding_dim=parameters['word_dim'],
hidden_dim=parameters['word_lstm_dim'],
use_gpu=parameters['use_gpu'],
char_to_ix=char_to_id,
pre_word_embeds=word_embeds,
use_crf=parameters['crf'],
char_mode=parameters['char_mode'])
Apply Quantization
model_int8 = torch.quantization.quantize_dynamic(
model_fp32, # the original model
{nn.LSTM,nn.Linear}, # a set of layers to dynamically quantize
dtype=torch.qint8)
Checking Quantization Results:
def print_size_of_model(model, label=""):
torch.save(model.state_dict(), "temp.p")
size=os.path.getsize("temp.p")
print("model: ",label,' \t','Size (KB):', size/1e3)
os.remove('temp.p')
return size
compare the sizes
f=print_size_of_model(model_fp32,"model_fp32")
q=print_size_of_model(model_int8,"model_int8")
print("{0:.2f} times smaller".format(f/q))
Results
model: model_fp32 Size (KB): 806494.996
model: model_int8 Size (KB): 804532.412 1.00 times smaller
is there any way to reduce the model size significantly??
Solution 1:[1]
Based on Results section of question and vocab_size of approximately 2 million, it's seems reasonable to quantize attribute word_embeds. Expected that quantization of only this module alone will result in significant drop of memory occupation by weights. According to documentation there is no support for dynamic quantization(which is used for nn.Linear and nn.LSTM in snippet above) of nn.Embedding(type of word_embeds), but static quantization can handle this. Default qconfig which is used in some pytorch examples seems not working on nn.Embedding, but there is a hint in issue discussion how to quantize nn.Embedding. After training:
from torch.quantization.qconfig import float_qparams_weight_only_qconfig
model_fp32.word_embeds.qconfig = float_qparams_weight_only_qconfig
torch.quantization.prepare(model_fp32, inplace=True)
torch.quantization.convert(model_fp32, inplace=True)
And after that word_embeds in model_fp32 will be quantized to torhc.quint8.
Sources
This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.
Source: Stack Overflow
| Solution | Source |
|---|---|
| Solution 1 | draw |