pytorch笔记：12)TVM-Pytorch模型编译体验+性能测试

tvm简介：https://zhuanlan.zhihu.com/p/88369758

实验环境

18.04.1-Ubuntu x86_64 x86_64 x86_64 GNU/Linux
CPU: 8  Intel(R) Core(TM) i7-6700 CPU @ 3.40GHz
tvm-0.7.dev1
torch-1.4.0
torchvision-0.5.0

tvm安装文档，另官网推荐使用torch不小于1.3.0

torch模型导出

使用torchvision自带的resnet18进行实验测试

import torch
import torchvision

model_name = 'resnet18'
model = getattr(torchvision.models, model_name)(pretrained=True)
# ~/.cache/torch/checkpoints/resnet18-5c106cde.pth
model = model.eval()

# We grab the TorchScripted model via tracing
input_shape = [1, 3, 224, 224]
input_data = torch.randn(input_shape)
#scripted_model不依赖python环境
scripted_model = torch.jit.trace(model, input_data).eval()

最后一句会提示警告，论坛帖子说这是正常的- -

WARNING:root:Untyped Tensor found, assume it is float

模型转换

torch模型到tvm模型的转换

#Convert PyTorch graph to Relay graph.
import tvm, time
from tvm import relay
input_name = 'input0'  # only one input, set it to this name
shape_list = [(input_name, input_shape)]
mod, params = relay.frontend.from_pytorch(scripted_model, shape_list)

tvm模型构建

使用导出的torch模型构建tvm模型

#Compile the graph to llvm target with given input specification
target = 'llvm'
target_host = 'llvm'
ctx = tvm.cpu(0)
with relay.build_config(opt_level=3):
    graph, lib, params = relay.build(mod, target=target, target_host=target_host, params=params)
#deploying the compiled model on target.
from tvm.contrib import graph_runtime
tvm_model = graph_runtime.create(graph, lib, ctx)
tvm_model.set_input(**params)

数据准备

随机生成1000张224*224的图片用于测试

import numpy as np
#考虑到随机生成的图片模型预测结果都一样，使用*(i % 9 + 1)让模型预测结果不同
list_img = [np.random.rand(1, 3, 224, 224).astype(np.float32) * (i % 9 + 1) for i in range(1000)]

tvm模型测试

1000张图片依次预测，结果返回预测类别和累计预测花费时间

def test_tvm(model, list_img):
    since = time.time()
    # 记录时间
    list_tpoint = []
    # 预测top1的类别
    list_top = []
    for img_x in list_img:
        model.set_input(input_name, tvm.nd.array(img_x))
        # Execute
        model.run()
        # Get outputs
        output = model.get_output(0)
        top1 = np.argmax(output.asnumpy()[0])
        list_top.append(top1)
        list_tpoint.append(time.time() - since)
    return list_top, list_tpoint

torch模型测试

输出结果同上

@torch.no_grad()
def test_torch(model, list_img):
    since = time.time()
    list_top = []
    list_tpoint = []
    for img_x in list_img:
        img_x = torch.from_numpy(img_x)
        output = model(img_x)
        top1 = np.argmax(output.numpy()[0])
        list_top.append(top1)
        list_tpoint.append(time.time() - since)
    return list_top, list_tpoint

结果分析

tvm_top,tvm_point=test_tvm(tvm_model,list_img)
torch_top,torch_points=test_torch(torch_model,list_img)
#打印2个模型耗费的时间
import matplotlib.pyplot as plt
plt.figure()
plt.plot(tvm_point,label='tvm')
plt.plot(torch_points,label='torch')
plt.legend()
plt.savefig('time_cost.png')
plt.show()

2个模型的部分预测结果

>>> tvm_top[:10]
[111, 111, 318, 818, 818, 644, 644, 644, 644, 111]
>>> torch_top[:10]
[111, 111, 318, 818, 818, 644, 644, 644, 644, 111]

2个模型预测耗时

>>> torch_points[-1]
53.492563009262085
>>> tvm_point[-1]
43.807936906814575

2个模型的累计时间花费图，横坐标为图片数，总坐标为耗时(秒)

小结：TVM相对原生态的torch在推理速度上还是有一定优势

reference:
https://zhuanlan.zhihu.com/p/88369758
https://docs.tvm.ai/tutorials/frontend/from_pytorch.html