mhc-mlx

High-performance MLX implementation of Manifold-Constrained Hyper-Connections (mHC).

mHC improves training stability and performance in deep architectures by constraining residual connections to the Birkhoff polytope (doubly stochastic matrices). This library provides optimized Metal kernels for Apple Silicon and a fast compiled fallback for other platforms.

Original Paper: mHC: Manifold-Constrained Hyper-Connections (DeepSeek-AI)

Installation

pip install mhc-mlx

Compatibility

• Primary: macOS + Apple Silicon for peak performance.
• Support: Linux (CPU/CUDA) and Intel Macs via automatic pure-MLX compiled fallback.
• Software: MLX >= 0.30.0.

Quick Start (30-second Demo)

import mlx.core as mx
import mlx.nn as nn
from mhc_mlx import MHCRewire

# 1. Take any standard MLX layer
layer = nn.Linear(2048, 2048)

# 2. Wrap it with mHC stability (automatically uses optimized Metal kernels)
model = MHCRewire(layer, dims=2048, n=32)

# 3. Run forward pass
x = mx.random.normal((1, 2048))
y = model(x)
mx.eval(y)

# 4. Run backward pass (fully vectorized)
loss_fn = lambda m, x: mx.sum(m(x))
grads = mx.grad(loss_fn)(model, x)
mx.eval(grads)

print(f"Output shape: {y.shape}") # (1, 2048)

Note: You can also use from mlx_mhc import MHCRewire for a community-friendly alias.

Performance

mhc-mlx utilizes fused Metal kernels to minimize memory bandwidth bottlenecks. We benchmarked on an Apple M4 Pro (macOS 15.6).

Comparative Benchmarks

Comparison with a standard MLX implementation of mHC ($C=512$):

Why It's Faster

Reproduce Benchmarks

Run the standardized benchmark suite on your own hardware:

mhc-mlx-bench --mode latency --C 512,2048,4096

Key Optimizations

• Universal Rewiring: MHCRewire wraps any existing nn.Module (Linear, Conv2d) to apply mHC dynamics.
• Quantized Layer Support: Seamlessly wraps nn.QuantizedLinear (4-bit/8-bit).
• Fully Fused Kernel: Single-pass kernel for Aggregate + RMS + Mix + Add.
• Adaptive Dispatch: Runtime heuristic selects the fastest kernel strategy for your workload.

Diagnostics

If you encounter issues, run the diagnostic utility:

mhc-mlx-info

Set MHC_MLX_DISABLE_METAL=1 in your environment to force the pure-MLX reference path (useful for debugging or non-Metal hardware).

Support Policy

• Tested: macOS (Apple Silicon) + Linux (CPU/CUDA) using MLX 0.30.0+.
• Best Effort: Intel Macs, older macOS versions, and older MLX versions.
• Reporting: Please include OS, MLX version, and mhc-mlx-info output in bug reports.

License

MIT