(资料图片仅供参考)
这几天又在玩树莓派，先是搞了个物联网，又在尝试在树莓派上搞一些简单的神经网络，这次搞得是卷积识别mnist手写数字识别
训练代码在电脑上，cpu就能训练，很快的：
import torchimport torch.nn as nnimport torch.optim as optimfrom torchvision import datasets, transformsimport numpy as np# 设置随机种子torch.manual_seed(42)# 定义数据预处理transform = transforms.Compose([ transforms.ToTensor(), # transforms.Normalize((0.1307,), (0.3081,))])# 加载训练数据集train_dataset = datasets.MNIST("data", train=True, download=True, transform=transform)train_loader = torch.utils.data.DataLoader(train_dataset, batch_size=64, shuffle=True)# 构建卷积神经网络模型class Net(nn.Module): def __init__(self): super(Net, self).__init__() self.conv1 = nn.Conv2d(1, 10, kernel_size=5) self.pool = nn.MaxPool2d(2) self.fc = nn.Linear(10 * 12 * 12, 10) def forward(self, x): x = self.pool(torch.relu(self.conv1(x))) x = x.view(-1, 10 * 12 * 12) x = self.fc(x) return xmodel = Net()# 定义损失函数和优化器criterion = nn.CrossEntropyLoss()optimizer = optim.SGD(model.parameters(), lr=0.01, momentum=0.5)# 训练模型def train(model, device, train_loader, optimizer, criterion, epochs): model.train() for epoch in range(epochs): for batch_idx, (data, target) in enumerate(train_loader): data, target = data.to(device), target.to(device) optimizer.zero_grad() output = model(data) loss = criterion(output, target) loss.backward() optimizer.step() if batch_idx % 100 == 0: print(f"Train Epoch: {epoch+1} [{batch_idx * len(data)}/{len(train_loader.dataset)} " f"({100. * batch_idx / len(train_loader):.0f}%)]\tLoss: {loss.item():.6f}")# 在GPU上训练（如果可用），否则使用CPUdevice = torch.device("cuda" if torch.cuda.is_available() else "cpu")model.to(device)# 训练模型train(model, device, train_loader, optimizer, criterion, epochs=5)# 保存模型为NumPy数据model_state = model.state_dict()numpy_model_state = {key: value.cpu().numpy() for key, value in model_state.items()}np.savez("model.npz", **numpy_model_state)print("Model saved as model.npz")然后需要自己在dataset里导出一些图片：我保存在了mnist_pi文件夹下,“_”后面的是标签，主要是在pc端导出保存到树莓派下
树莓派推理端的代码，需要numpy手动重新搭建网络，并且需要手动实现conv2d卷积神经网络和maxpool2d最大池化，然后加载那些保存的矩阵参数，做矩阵乘法和加法
import numpy as npimport osfrom PIL import Imagedef conv2d(input, weight, bias, stride=1, padding=0): batch_size, in_channels, in_height, in_width = input.shape out_channels, in_channels, kernel_size, _ = weight.shape # 计算输出特征图的大小 out_height = (in_height + 2 * padding - kernel_size) // stride + 1 out_width = (in_width + 2 * padding - kernel_size) // stride + 1 # 添加padding padded_input = np.pad(input, ((0, 0), (0, 0), (padding, padding), (padding, padding)), mode="constant") # 初始化输出特征图 output = np.zeros((batch_size, out_channels, out_height, out_width)) # 执行卷积操作 for b in range(batch_size): for c_out in range(out_channels): for h_out in range(out_height): for w_out in range(out_width): h_start = h_out * stride h_end = h_start + kernel_size w_start = w_out * stride w_end = w_start + kernel_size # 提取对应位置的输入图像区域 input_region = padded_input[b, :, h_start:h_end, w_start:w_end] # 计算卷积结果 x = input_region * weight[c_out] bia = bias[c_out] conv_result = np.sum(x, axis=(0,1, 2)) + bia # 将卷积结果存储到输出特征图中 output[b, c_out, h_out, w_out] = conv_result return outputdef max_pool2d(input, kernel_size, stride=None, padding=0): batch_size, channels, in_height, in_width = input.shape if stride is None: stride = kernel_size out_height = (in_height - kernel_size + 2 * padding) // stride + 1 out_width = (in_width - kernel_size + 2 * padding) // stride + 1 padded_input = np.pad(input, ((0, 0), (0, 0), (padding, padding), (padding, padding)), mode="constant") output = np.zeros((batch_size, channels, out_height, out_width)) for b in range(batch_size): for c in range(channels): for h_out in range(out_height): for w_out in range(out_width): h_start = h_out * stride h_end = h_start + kernel_size w_start = w_out * stride w_end = w_start + kernel_size input_region = padded_input[b, c, h_start:h_end, w_start:w_end] output[b, c, h_out, w_out] = np.max(input_region) return output# 加载保存的模型数据model_data = np.load("model.npz")# 提取模型参数conv_weight = model_data["conv1.weight"]conv_bias = model_data["conv1.bias"]fc_weight = model_data["fc.weight"]fc_bias = model_data["fc.bias"]# 进行推理def inference(images): # 执行卷积操作 conv_output = conv2d(images, conv_weight, conv_bias, stride=1, padding=0) conv_output = np.maximum(conv_output, 0) # ReLU激活函数 #maxpool2d pool = max_pool2d(conv_output,2) # 执行全连接操作 flattened = pool.reshape(pool.shape[0], -1) fc_output = np.dot(flattened, fc_weight.T) + fc_bias fc_output = np.maximum(fc_output, 0) # ReLU激活函数 # 获取预测结果 predictions = np.argmax(fc_output, axis=1) return predictionsfolder_path = "./mnist_pi" # 替换为图片所在的文件夹路径def infer_images_in_folder(folder_path): for file_name in os.listdir(folder_path): file_path = os.path.join(folder_path, file_name) if os.path.isfile(file_path) and file_name.endswith((".jpg", ".jpeg", ".png")): image = Image.open(file_path) label = file_name.split(".")[0].split("_")[1] image = np.array(image)/255.0 image = np.expand_dims(image,axis=0) image = np.expand_dims(image,axis=0) print("file_path:",file_path,"img size:",image.shape,"label:",label) predicted_class = inference(image) print("Predicted class:", predicted_class)infer_images_in_folder(folder_path)这代码完全就是numpy推理，不需要安装pytorch，树莓派也装不动pytorch，太重了，下面是推理结果，比之前的MLP网络慢很多，主要是手动实现的卷积网络全靠循环实现。
那我们给它加加速吧，下面是一个多线程加速程序：
import numpy as npimport osfrom PIL import Imagefrom multiprocessing import Pooldef conv2d(input, weight, bias, stride=1, padding=0): batch_size, in_channels, in_height, in_width = input.shape out_channels, in_channels, kernel_size, _ = weight.shape # 计算输出特征图的大小 out_height = (in_height + 2 * padding - kernel_size) // stride + 1 out_width = (in_width + 2 * padding - kernel_size) // stride + 1 # 添加padding padded_input = np.pad(input, ((0, 0), (0, 0), (padding, padding), (padding, padding)), mode="constant") # 初始化输出特征图 output = np.zeros((batch_size, out_channels, out_height, out_width)) # 执行卷积操作 for b in range(batch_size): for c_out in range(out_channels): for h_out in range(out_height): for w_out in range(out_width): h_start = h_out * stride h_end = h_start + kernel_size w_start = w_out * stride w_end = w_start + kernel_size # 提取对应位置的输入图像区域 input_region = padded_input[b, :, h_start:h_end, w_start:w_end] # 计算卷积结果 x = input_region * weight[c_out] bia = bias[c_out] conv_result = np.sum(x, axis=(0,1, 2)) + bia # 将卷积结果存储到输出特征图中 output[b, c_out, h_out, w_out] = conv_result return outputdef max_pool2d(input, kernel_size, stride=None, padding=0): batch_size, channels, in_height, in_width = input.shape if stride is None: stride = kernel_size out_height = (in_height - kernel_size + 2 * padding) // stride + 1 out_width = (in_width - kernel_size + 2 * padding) // stride + 1 padded_input = np.pad(input, ((0, 0), (0, 0), (padding, padding), (padding, padding)), mode="constant") output = np.zeros((batch_size, channels, out_height, out_width)) for b in range(batch_size): for c in range(channels): for h_out in range(out_height): for w_out in range(out_width): h_start = h_out * stride h_end = h_start + kernel_size w_start = w_out * stride w_end = w_start + kernel_size input_region = padded_input[b, c, h_start:h_end, w_start:w_end] output[b, c, h_out, w_out] = np.max(input_region) return output# 加载保存的模型数据model_data = np.load("model.npz")# 提取模型参数conv_weight = model_data["conv1.weight"]conv_bias = model_data["conv1.bias"]fc_weight = model_data["fc.weight"]fc_bias = model_data["fc.bias"]# 进行推理def inference(images): # 执行卷积操作 conv_output = conv2d(images, conv_weight, conv_bias, stride=1, padding=0) conv_output = np.maximum(conv_output, 0) # ReLU激活函数 # maxpool2d pool = max_pool2d(conv_output, 2) # 执行全连接操作 flattened = pool.reshape(pool.shape[0], -1) fc_output = np.dot(flattened, fc_weight.T) + fc_bias fc_output = np.maximum(fc_output, 0) # ReLU激活函数 # 获取预测结果 predictions = np.argmax(fc_output, axis=1) return predictionslabels = []preds = []def infer_image(file_path): image = Image.open(file_path) label = file_path.split("/")[-1].split(".")[0].split("_")[1] image = np.array(image) / 255.0 image = np.expand_dims(image, axis=0) image = np.expand_dims(image, axis=0) print("file_path:", file_path, "img size:", image.shape, "label:", label) predicted_class = inference(image) print("Predicted class:", predicted_class)folder_path = "./mnist_pi" # 替换为图片所在的文件夹路径pool = Pool(processes=4) # 设置进程数为2，可以根据需要进行调整def infer_images_in_folder(folder_path): for file_name in os.listdir(folder_path): file_path = os.path.join(folder_path, file_name) if os.path.isfile(file_path) and file_name.endswith((".jpg", ".jpeg", ".png")): pool.apply_async(infer_image, args=(file_path,)) pool.close() pool.join()infer_images_in_folder(folder_path)下图可以看出来，我的树莓派3b+，cpu直接拉满，速度提升4倍：
营业执照公示信息