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Neural Network Forward Pass Example - Jax Typing CST Test
Neural Network Forward Pass Example — Jax Code
Forward pass of a simple 2-layer neural network in JAX.
import jax.numpy as jnp
# Input
x = jnp.array([1.0, 2.0, 3.0])
# Network parameters
W1 = jnp.array([[0.1,0.2,0.3],[0.4,0.5,0.6]])
b1 = jnp.array([0.1,0.2])
W2 = jnp.array([[0.7,0.8]])
b2 = jnp.array([0.3])
# Forward pass
def relu(x):
return jnp.maximum(0, x)
h = relu(jnp.dot(W1, x) + b1)
y_pred = jnp.dot(W2, h) + b2
print('Output:', y_pred)Jax Language Guide
JAX is an open-source Python library for high-performance numerical computing, combining NumPy-like API with automatic differentiation (autograd), GPU/TPU acceleration, and composable function transformations for machine learning and scientific computing.
Primary Use Cases
- ▸High-performance machine learning and deep learning model development
- ▸Gradient-based optimization and automatic differentiation
- ▸Physics simulations and scientific computing requiring differentiable functions
- ▸Research in reinforcement learning and generative models
- ▸GPU/TPU accelerated numerical computing at scale
Notable Features
- ▸NumPy-compatible API with hardware acceleration
- ▸Automatic differentiation with `grad`
- ▸Just-in-time compilation (`jit`) for optimized performance
- ▸Vectorization (`vmap`) and parallelization (`pmap`) of functions
- ▸Composable transformations for advanced research pipelines
Origin & Creator
JAX was developed by researchers at Google Research starting in 2018, building on Autograd and XLA (Accelerated Linear Algebra) to enable high-performance, differentiable programming.
Industrial Note
JAX is widely used in cutting-edge machine learning research, physics simulations, reinforcement learning, and differentiable programming, where composable gradients and hardware acceleration are essential.
Quick Explain
- ▸JAX provides a NumPy-compatible API with hardware acceleration on CPU, GPU, and TPU.
- ▸It offers automatic differentiation for gradients of arbitrary Python functions using `grad`, `vmap`, `jit`, and `pmap`.
- ▸JAX enables composable transformations like vectorization, parallelization, and just-in-time compilation, making it ideal for research and large-scale ML experiments.
Core Features
- ▸Autograd for forward- and reverse-mode differentiation
- ▸JIT compilation for CPU/GPU/TPU performance
- ▸Vectorized operations over batches with `vmap`
- ▸Parallel computation across devices with `pmap`
- ▸Random number generation with functional, reproducible API
Learning Path
- ▸Learn Python and NumPy fundamentals
- ▸Understand functional programming principles
- ▸Practice autograd and `grad` on simple functions
- ▸Experiment with `jit`, `vmap`, and `pmap`
- ▸Build research or ML pipelines using Flax/Optax/JAX
Practical Examples
- ▸Compute gradient of a scalar function with `grad`
- ▸Train a simple neural network using JAX arrays and `grad`
- ▸Vectorize loss computation over a batch with `vmap`
- ▸JIT-compile a physics simulation for GPU execution
- ▸Parallelize reinforcement learning environment rollout across multiple GPUs using `pmap`
Comparisons
- ▸JAX vs NumPy: JAX adds autograd, JIT, vmap, pmap, GPU/TPU support
- ▸JAX vs TensorFlow: JAX is functional, research-focused, flexible; TensorFlow has higher-level APIs and production tools
- ▸JAX vs PyTorch: JAX uses functional programming and composable transformations; PyTorch is imperative and popular for production
- ▸JAX vs Numpy+Autograd: JAX is faster, supports hardware acceleration and composable transforms
- ▸JAX vs MATLAB: JAX is Python-first, differentiable, and GPU/TPU compatible
Strengths
- ▸Extremely fast and hardware-optimized for large computations
- ▸Highly composable functional transformations
- ▸Seamless integration with NumPy and SciPy
- ▸Strong support for research in ML and differentiable programming
- ▸Works efficiently on TPUs and multi-GPU clusters
Limitations
- ▸Steep learning curve for beginners in functional programming style
- ▸Limited ecosystem compared to TensorFlow or PyTorch for high-level models
- ▸Debugging JIT-compiled code can be tricky
- ▸Some Python libraries are incompatible with JAX’s functional transformations
- ▸Primarily research-focused; fewer production deployment utilities
When NOT to Use
- ▸Quick prototyping for simple computations on CPU
- ▸Projects needing extensive high-level ML framework support
- ▸Non-research applications with no need for gradient computation
- ▸Legacy codebases not compatible with functional transformations
- ▸Very small scripts where JIT or GPU acceleration overhead outweighs benefits
Cheat Sheet
- ▸Array = JAX array (like NumPy)
- ▸grad(f) = derivative of function f
- ▸jit(f) = compiled function for speed
- ▸vmap(f) = vectorized map over batches
- ▸pmap(f) = parallel map across devices
FAQ
- ▸Is JAX free?
- ▸Yes - open-source under Apache 2.0 license.
- ▸Which devices are supported?
- ▸CPU, GPU, and TPU (via XLA backend).
- ▸Can JAX compute gradients automatically?
- ▸Yes - using `grad` for scalar or vector functions.
- ▸Is JAX suitable for deep learning?
- ▸Yes - often used with Flax or Haiku for neural networks.
- ▸Can JAX scale to multiple devices?
- ▸Yes - `pmap` allows parallelization across GPUs/TPUs.
30-Day Skill Plan
- ▸Week 1: NumPy-like computations and arrays
- ▸Week 2: Automatic differentiation with `grad`
- ▸Week 3: JIT compilation and benchmarking
- ▸Week 4: Vectorization with `vmap` and parallelization with `pmap`
- ▸Week 5: Full ML pipelines with Flax/Optax and TPU/GPU acceleration
Final Summary
- ▸JAX is a high-performance Python library for numerical computing with autograd, JIT, and hardware acceleration.
- ▸Enables functional, composable, and differentiable programming.
- ▸Ideal for ML research, scientific computing, and TPU/GPU-accelerated pipelines.
- ▸Integrates seamlessly with Optax, Flax, and Haiku for deep learning.
- ▸Supports vectorization, parallelization, and scalable numerical computation.
Project Structure
- ▸scripts/ - JAX model and function scripts
- ▸datasets/ - input data for training or simulations
- ▸notebooks/ - exploratory computation and experimentation
- ▸models/ - saved parameters or checkpoints
- ▸logs/ - performance metrics and experiment tracking
Monetization
- ▸Research consulting using JAX pipelines
- ▸Scientific simulations for enterprise clients
- ▸ML model development and optimization
- ▸High-performance computing services
- ▸Training workshops and tutorials
Productivity Tips
- ▸Use JIT to accelerate heavy computations
- ▸Vectorize functions instead of Python loops
- ▸Keep functions pure for composability
- ▸Cache and reuse compiled functions
- ▸Leverage multi-device parallelism with `pmap`
Basic Concepts
- ▸Array: JAX’s primary data structure, similar to NumPy arrays
- ▸grad: computes derivatives of functions automatically
- ▸jit: compiles Python functions for optimized execution
- ▸vmap: vectorizes functions over batch dimensions
- ▸pmap: parallelizes functions across multiple devices