import torch
target_platform = "proxyless_cpu"
# proxyless_gpu, proxyless_mobile, proxyless_mobile14 are also avaliable.
model = torch.hub.load('mit-han-lab/ProxylessNAS', target_platform, pretrained=True)
model.eval()
所有预训练模型都需要按照相同方式归一化输入图像,即形状为 (3 x H x W)
的 3 通道 RGB 图像 mini-batch,其中 H
和 W
预期至少为 224
。图像必须加载到 [0, 1]
范围内,然后使用 mean = [0.485, 0.456, 0.406]
和 std = [0.229, 0.224, 0.225]
进行归一化。
以下是一个示例执行过程。
# Download an example image from the pytorch website
import urllib
url, filename = ("https://github.com/pytorch/hub/raw/master/images/dog.jpg", "dog.jpg")
try: urllib.URLopener().retrieve(url, filename)
except: urllib.request.urlretrieve(url, filename)
# sample execution (requires torchvision)
from PIL import Image
from torchvision import transforms
input_image = Image.open(filename)
preprocess = transforms.Compose([
transforms.Resize(256),
transforms.CenterCrop(224),
transforms.ToTensor(),
transforms.Normalize(mean=[0.485, 0.456, 0.406], std=[0.229, 0.224, 0.225]),
])
input_tensor = preprocess(input_image)
input_batch = input_tensor.unsqueeze(0) # create a mini-batch as expected by the model
# move the input and model to GPU for speed if available
if torch.cuda.is_available():
input_batch = input_batch.to('cuda')
model.to('cuda')
with torch.no_grad():
output = model(input_batch)
# Tensor of shape 1000, with confidence scores over ImageNet's 1000 classes
print(output[0])
# The output has unnormalized scores. To get probabilities, you can run a softmax on it.
probabilities = torch.nn.functional.softmax(output[0], dim=0)
print(probabilities)
# Download ImageNet labels
!wget https://raw.githubusercontent.com/pytorch/hub/master/imagenet_classes.txt
# Read the categories
with open("imagenet_classes.txt", "r") as f:
categories = [s.strip() for s in f.readlines()]
# Show top categories per image
top5_prob, top5_catid = torch.topk(probabilities, 5)
for i in range(top5_prob.size(0)):
print(categories[top5_catid[i]], top5_prob[i].item())
模型描述
ProxylessNAS 模型来自论文 ProxylessNAS: 在目标任务和硬件上直接进行神经架构搜索。
传统上,人们倾向于为所有硬件平台设计一个高效模型。但不同的硬件具有不同的属性,例如 CPU 具有更高的频率,而 GPU 更擅长并行化。因此,我们需要的不是泛化,而是为不同的硬件平台定制 CNN 架构。如下所示,在相似的准确率下,定制化在所有三个平台上都提供了免费且显著的性能提升。
模型结构 | GPU 延迟 | CPU 延迟 | 移动设备延迟 |
---|---|---|---|
proxylessnas_gpu | 5.1ms | 204.9ms | 124ms |
proxylessnas_cpu | 7.4ms | 138.7ms | 116ms |
proxylessnas_mobile | 7.2ms | 164.1ms | 78ms |
下表列出了使用预训练模型对应的 top-1 准确率。
模型结构 | Top-1 错误率 |
---|---|
proxylessnas_cpu | 24.7 |
proxylessnas_gpu | 24.9 |
proxylessnas_mobile | 25.4 |
proxylessnas_mobile_14 | 23.3 |