GitHub - bwiemz/NSL: A statically-typed, compiled programming language designed as a first-class replacement for Python + PyTorch in AI/ML workloads.

NeuralScript (NSL)

A statically-typed, compiled programming language designed as a first-class replacement for Python + PyTorch in AI/ML workloads.

NSL compiles to native code via Cranelift with zero Python or C++ dependencies. The entire stack is Rust (compiler + runtime) and NSL (standard library).

Why NSL?

Python-familiar syntax with indentation-based blocks, let/const, fn, model
Compile-time tensor shape checking — catch dimension mismatches before running
Native autodiff — grad(...) and train(...) use tape AD by default, with --source-ad for compile-time lowering when possible
Declarative training — train blocks replace boilerplate training loops
GPU/CUDA native — kernel keyword for custom GPU ops, .to(cuda) for device transfer
No GIL, no runtime — just nsl run model.nsl

Installation

From GitHub Releases

Download the latest release from GitHub Releases.

# Linux/macOS
tar xzf nsl-v0.9.0-<target>.tar.gz
export PATH="$PWD/nsl-v0.9.0-<target>/bin:$PATH"

Important: Keep nsl binary alongside the lib/ directory — the compiler needs lib/libnsl_runtime.a and lib/stdlib/.

Prerequisites

Linux/macOS: C compiler (gcc or clang) — usually pre-installed
Windows: Visual Studio Build Tools (MSVC link.exe)
GPU (optional): NVIDIA CUDA Toolkit

From Source

git clone https://github.com/bwiemz/NSL.git
cd NSL
cargo build --release -p nsl-cli

Quick Start

nsl init myproject
cd myproject
nsl run main.nsl

Contributing? See docs/wiki/ for architecture, roadmap, and how to extend the compiler.

Tutorial: Build a Transformer from Scratch

1. Define a Model

from nsl.nn.norms import RMSNorm
from nsl.nn.losses import cross_entropy

model MLP:
    w1: Tensor = randn([512, 1408]) * full([1], 0.02)
    w2: Tensor = randn([1408, 512]) * full([1], 0.02)
    norm: RMSNorm = RMSNorm(512)

    fn forward(self, x: Tensor) -> Tensor:
        let h = self.norm.forward(x)
        let gate = silu(h @ self.w1)
        return gate @ self.w2

2. Train It

from nsl.nn.losses import mse_loss

let m = MLP()
let x = randn([32, 512])
let y = randn([32, 512])

train(model=m, epochs=100):
    optimizer: AdamW(lr=0.001, weight_decay=0.01)
    scheduler: cosine_anneal(min_lr=0.0001)
    step(batch):
        let pred = m.forward(x)
        let loss = mse_loss(pred, y)
    callbacks:
        on_step(step, loss):
            if step % 10 == 0:
                print(loss)

3. Save and Load

model_save(m, "checkpoint.nslm")
# ... later ...
model_load(m, "checkpoint.nslm")

4. Run on GPU

let m = MLP()
let x = randn([32, 512]).to(cuda)
let pred = m.forward(x)

5. Custom GPU Kernels

kernel vec_add(a, b, c):
    let i = thread_id()
    c[i] = a[i] + b[i]

let a = full([1024], 1.0).to(cuda)
let b = full([1024], 2.0).to(cuda)
let c = zeros([1024]).to(cuda)
vec_add(a, b, c, grid=4, block=256)

6. Pretrain on Real Data

from model import NSLCoder
from nsl.nn.losses import cross_entropy

let m = NSLCoder()
let tokens = load_mmap("data/tokens.bin", 3)
let loader = DataLoader(tokens, batch_size=32, seq_len=1024, shuffle=true)

for batch in loader:
    let logits = m.forward_train(batch.input_ids, true)
    let loss = cross_entropy(logits, batch.labels)
    print(loss)

Autodiff Modes

NSL uses tape-based reverse-mode AD by default for train(...) and standalone grad(...) blocks. Pass --source-ad to ask the compiler to lower supported static graphs at compile time instead.

If source AD cannot extract or resolve a supported gradient graph, NSL emits a diagnostic and falls back to tape AD rather than changing program behavior.

CLI Reference

nsl run file.nsl                    # Run a program
nsl build file.nsl                  # Compile to native executable
nsl check file.nsl                  # Type-check without running
nsl fmt file.nsl                    # Format code
nsl test tests/*.nsl                # Run test suite

# Autodiff backend selection
nsl run --source-ad file.nsl        # Prefer compile-time source-to-source AD
nsl run --tape-ad file.nsl          # Force runtime tape AD

# Compile-time analysis
nsl check --perf file.nsl           # Roofline performance analysis
nsl check --nan-analysis file.nsl   # NaN/Inf risk detection
nsl check --deterministic file.nsl  # Determinism verification

# GPU build
nsl build file.nsl --features cuda  # Enable GPU support
nsl run file.nsl --target cuda      # Run with CUDA backend

# Unikernel deployment
nsl build file.nsl --unikernel --listen 0.0.0.0:8080 --memory 16G

# ZK proof generation
nsl build --zk file.nsl             # Generate ZK proof
nsl zk verify proof.zkp             # Verify a proof
nsl zk stats proof.zkp              # Proof statistics

Project Structure

crates/
  nsl-lexer/       Tokenizer (indentation-aware)
  nsl-ast/         Abstract syntax tree definitions
  nsl-parser/      Recursive descent parser
  nsl-semantic/    Type checking, shape inference, name resolution
  nsl-codegen/     Cranelift IR generation and native compilation
  nsl-runtime/     Rust static library linked into every NSL binary
  nsl-cli/         Command-line interface

stdlib/nsl/        Standard library (written in NSL)
  nn/              Neural network layers, norms, losses, attention
  optim/           Optimizers and learning rate schedulers
  tokenize/        Tokenizer wrappers

spec/              Language specification (13 chapters)
examples/          Example programs and integration tests
models/            Reference model implementations
benchmarks/        Performance benchmarks
docs/              Design documents, plans, and summaries
  research/        Research PDFs and source collections

Benchmarks

All benchmarks run on CPU (AMD 9800X3D, 64GB RAM). GPU benchmarks require --features cuda.

Operator Fusion (M31)

Chains of elementwise ops are fused into a single loop — zero intermediate tensor allocations.

Chain	Fused	Unfused	Speedup
`sigmoid(relu(a + b))` on [1000,1000]	3.45 ms, 1 alloc, 4 MB	8.67 ms, 2 allocs, 8 MB	2.5x
`sigmoid(tanh(relu(a + b)))` on [256,512]	32.3 ms, 20 allocs	52.7 ms, 40 allocs	1.6x

Fusion is automatic and preserves numerical correctness. Disable with --disable-fusion for differential testing.

DataLoader Throughput (M19)

Config	Throughput
batch=1, seq=1024	270K batches/sec, 277M tokens/sec
batch=32, seq=1024	9.3K batches/sec, 306M tokens/sec

The DataLoader reads pre-tokenized u16 data via zero-copy mmap. Causal attention masks are generated inside the model's GQA layer, not in the DataLoader.

Roofline Cost Model (M37)

Per-op analysis of the NSLCoder-50M forward pass (H100-SXM target):

Operation	GFLOPs	AI (FLOP/byte)	Bound
Q/K/V projections	0.27-0.54	73-102	Compute
Attention QK^T	1.07	28.4	Compute
Softmax	0.04	0.625	Memory
FFN matmuls	1.48	137.4	Compute
LM head	51.5	169.5	Compute

Full forward pass: 117.5 GFLOPs, overall AI = 63.9 FLOP/byte. Memory-bound at batch=1 (softmax and elementwise ops dominate); compute-bound at batch=32.

Training Correctness

$ nsl run examples/m14_sgd_basic.nsl
4.0                    # epoch 1: mse_loss = 4.0 (correct for ones([2,1]) weights)
3.6863999366760254     # epoch 2: gradient descent working
3.397386074066162      # epoch 3: loss decreasing
3.1310312747955322     # epoch 4
2.8855583667755127     # epoch 5

Validation commands live in .github/workflows/ci.yml. The current local snapshot for this checkout is:

cargo build --workspace ✅
cargo test --workspace -- --skip e2e_ ❌ currently fails in crates/nsl-cli/tests/cpdt_cli.rs::bare_cpdt_report_enables_full_mode
cargo test -p nsl-cli --test e2e -- --test-threads=1 ❌ currently reports widespread failures in this environment, including OpenSSL linker errors

Recommended Training Config (RTX 5070 Ti, 16GB VRAM)

# models/coder50m/config.nsl
const PRETRAIN_BATCH_SIZE = 32     # ~83% VRAM utilization, compute-bound
const PRETRAIN_LR = 0.0003
const PRETRAIN_WARMUP = 3000
const PRETRAIN_GRAD_CLIP = 1.0

Testing

cargo test --workspace              # Run the workspace unit and integration tests
cargo test --workspace -- --skip e2e_  # Match the main CI unit-test step
cargo test -p nsl-cli --test e2e -- --test-threads=1  # Run the CLI smoke/e2e suite
cargo run -p nsl-cli -- run examples/m14_sgd_basic.nsl  # Training demo
cargo run -p nsl-cli -- test tests/m15_test.nsl          # NSL test suite

# Run benchmarks
cargo run -p nsl-cli --release -- run benchmarks/bench_fusion_metrics.nsl
cargo run -p nsl-cli --release -- run benchmarks/bench_roofline.nsl

Documentation

SPECIFICATION.md — Full feature reference, architecture, per-op roofline analysis
spec/ — Formal language specification (13 chapters)
docs/research/ — Research PDFs and source notes used to shape the roadmap
docs/summaries/ — Condensed technical summaries for each subsystem
docs/plans/ — Roadmap and future milestone designs

Contributing

NSL is structured as a standard Rust workspace. To get started:

git clone https://github.com/bwiemz/NSL.git
cd NSL
cargo build                         # Build all crates
cargo test --workspace              # Run the full workspace test suite
cargo run -p nsl-cli -- run examples/m14_sgd_basic.nsl  # Run a training example

Key entry points for contributors:

Add a tensor op: crates/nsl-runtime/src/tensor/ — implement the op, add to builtins.rs
Add an AD rule: crates/nsl-runtime/src/autodiff/backward.rs — add a TapeOp variant and backward logic
Add a stdlib layer: stdlib/nsl/nn/ — pure NSL, no Rust needed
Add a language feature: Parser → AST → Semantic → Codegen pipeline across the 4 crates

Known Limitations

No REPL
CUDA required for GPU features (ROCm/Metal/WebGPU KIR built, untested on real hardware)
Windows requires Visual Studio Build Tools for linking
Fusion fires on elementwise chains; matmul+epilogue fusion (fused bias+relu inside matmul) is analysis-only

License

Apache 2.0

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