TNN: A C/C++ Deep Learning Tensor Neural Network Library Built from Scratch

TNN is an open-source deep learning library developed and maintained by tungphambasement, released on GitHub in May 2026 (link: https://github.com/tungphambasement/TNN). It is fully implemented from scratch using C/C++ without relying on existing deep learning frameworks. Its core goal is to help developers deeply understand the underlying principles of deep learning, including tensor operations, automatic differentiation, forward/backward propagation of neural network layers, optimizer logic, etc.

While advanced frameworks like PyTorch and TensorFlow are convenient, they hide a lot of underlying details. For learners who want to understand the working principles of neural networks, it is difficult to grasp the core mechanisms using only high-level APIs. The TNN project aims to solve this problem; through its code, one can deeply learn about tensor data structures, automatic differentiation implementation, neural network layer computation, optimizer update logic, and loss function derivation, etc.

The value of using C/C++ to build TNN:

1. Performance Advantages: Fine-grained memory management, avoiding unnecessary copies, and using SIMD instructions to achieve efficiency close to hardware limits;
2. Educational Value: Static typing and explicit memory management force developers to think about data structure layout and lifecycle, deepening their understanding of the essence of algorithms;
3. Cross-platform Capability: Can run on various environments such as embedded systems, mobile devices, and servers, suitable for resource-constrained scenarios.

TNN includes five core modules:

1. Tensor Engine: Supports multi-dimensional array storage, memory layout optimization, broadcasting mechanism, and device abstraction;
2. Automatic Differentiation System: Records operation history during forward propagation, computes gradients using the chain rule, handles in-place operations and memory optimization;
3. Neural Network Layers: Implements linear layers, convolutional layers, activation functions (ReLU/Sigmoid, etc.), normalization layers, and Dropout;
4. Loss Functions: Supports mean squared error, cross-entropy, and custom losses;
5. Optimizers: Provides SGD (with momentum), Adam, and learning rate scheduling strategies.

Strategies for building a deep learning library from scratch:

• Memory Management: Reference counting to track tensor usage, memory pool pre-allocation to reduce overhead, RAII pattern to ensure resource release;
• Numerical Stability: Stable Softmax implementation (subtract maximum value to avoid overflow), log-sum-exp technique, gradient clipping to prevent explosion;
• Parallel Computing: OpenMP multi-threading acceleration, SIMD vectorization, integration with BLAS libraries to optimize matrix operations.

Value of TNN for developers at different levels:

• Beginners: Understand tensor shapes, broadcasting mechanisms, gradient descent, and backpropagation; it is recommended to start practicing with linear regression;
• Experienced Developers: Compare design differences with frameworks like PyTorch, study tensor memory layout, automatic differentiation strategies, and performance optimization;
• System Developers: Focus on module interface design, balance between performance and readability, and completeness of error handling.

Expansion directions for TNN:

• Feature Expansion: Add Transformer/LSTM layers, data loaders, model serialization, and GPU support;
• Performance Optimization: Operator fusion, graph optimization, quantization support;
• Documentation and Examples: Improve tutorials, API documentation, and MNIST/CIFAR-10 training examples. The community can participate in the project's development by contributing code, documentation, or feedback.

TNN embodies the concept of 'knowing not only what but also why' in deep learning education. In today's era of popular advanced frameworks, its approach of building from scratch provides developers with resources to deeply understand underlying mechanisms. Compared to similar C++ libraries like tinygrad and darknet, TNN is education-oriented with concise and readable code. Mastering its underlying principles helps in debugging complex models, optimizing training performance, and developing new algorithms.