tang

Differentiable computing in Rust.

use tang::*;
use tang_la::{DVec, DMat, Svd};
use tang_ad::{Tape, grad};
use tang_optim::Adam;

// Dual numbers give you exact derivatives for free
let x = Dual::new(2.0, 1.0);
let y = (x * x).sin(); // y.dual = cos(x²) · 2x

// Reverse-mode AD for large parameter spaces
let loss = |x: &[f64]| x[0]*x[0] + x[1]*x[1] + x[2]*x[2];
let g = grad(loss, &[1.0, 2.0, 3.0]); // [2, 4, 6]

// Dense linear algebra — LU, SVD, Cholesky, QR, Eigen
let a = DMat::from_fn(3, 3, |i, j| if i == j { 2.0 } else { -1.0 });
let svd = Svd::new(&a);

// The same Scalar trait flows through everything
let q = Quat::axis_angle(Dir3::Z, core::f64::consts::FRAC_PI_2);
let v = q.rotate(Vec3::new(1.0, 0.0, 0.0)); // ≈ (0, 1, 0)

                          tang
                    ┌───────┴───────┐
                 tang-la          tang-expr
              ┌────┼────┐        ┌──┴──┐
        tang-sparse  tang-ad  tang-gpu  │
                        │      ↗       │
                   tang-optim  tang-tensor
                        │     ╱  │      │
                   tang-train    │   tang-mesh
                                 │
                       tang-safetensors
                                 │
                              tang-hub

Arrows point from dependee → dependent. Two independent trees (tang-la for algebra, tang-expr for symbolic computation) converge at tang-tensor and tang-gpu.

One Scalar trait. f32, f64, and Dual<S> all implement Scalar. Write your physics once, get exact derivatives by swapping the type parameter. Forward-mode for small systems, reverse-mode for large ones.

Two paths to GPU. tang-expr traces Rust math into a symbolic DAG, then compiles to WGSL. tang-gpu dispatches the compiled kernels. Element-wise chains fuse into a single kernel automatically.

no_std throughout. Every crate is #![no_std] with alloc. Use tang on embedded, in WASM, wherever.

No heavyweight dependencies. Core types are hand-rolled #[repr(C)] with optional bytemuck and serde support. Dense LA is native Rust, generic over Scalar.

Fast on the CPU, by default. DMat::mul_mat and Tensor::matmul route through tang-la::gemm — cache-blocked, register-tiled, and NEON-vectorized for f32/f64, with the generic Scalar path (Dual, and anything else you impl) kept intact behind the same API. --features threads splits the work across a rayon pool; --features accelerate dispatches to Apple's AMX on macOS. See BENCHMARKS.md for numbers and for what is still on the table (x86 SIMD is not written yet).

Opt-in float reassociation. The algebraic feature compiles reduction inner loops (Scalar::alg_add/alg_sub/alg_mul) to Rust's algebraic_* ops, letting the compiler reorder and vectorize float chains — ~4x on dot products. Two caveats. First, results drift ~1 ulp per element versus a strict build, so skip it if you have a pinned numeric baseline. Second, cargo features are additive and global: if any crate in your dependency graph enables tang/algebraic, it is on for every tang consumer in that build, and you cannot opt out locally. Code whose evaluation order is load-bearing — the exact predicates in crates/tang/src/predicates.rs, the SVD Jacobi sweeps, any compensated summation — never uses the alg_* ops and is unaffected; crates/tang/tests/algebraic_forbidden.rs enforces that. algebraic and exact are compatible on purpose, since boolean geometry wants exact predicates and fast solvers at once.

Physics-native ML. The same types that run your constraint solver and physics engine also train your neural nets. tang-tensor → tang-ad → tang-optim → tang-train is a complete differentiable programming stack.

Distributed by default. tang-mesh ships expression graphs — not tensors — over QUIC. Each worker compiles locally to its own GPU backend. Data-parallel, pipeline-parallel, and tensor-parallel strategies with fault tolerance.

cargo add tang tang-la tang-ad

use tang::{Vec3, Quat, Dual, Scalar};
use tang_la::{DVec, DMat, Lu};
use tang_ad::grad;

tang provides drop-in compatibility aliases so you can migrate from nalgebra with minimal call-site changes.

Both by-value and by-reference calling conventions work:

// nalgebra style (by-ref) — works
v.dot(&w);
v.cross(&w);

// tang style (by-value) — also works
v.dot(w);
v.cross(w);

Aliases provided for common nalgebra names:

All benchmarks on Apple M-series, single-threaded. Run with cargo bench -p tang-bench.

tang's key advantage: the same code that runs your physics also gives you exact derivatives. Write your simulation once with generic S: Scalar, then swap in Dual<f64> to get gradients, Jacobians, and Hessians — no finite differences, no truncation error.

The speed comparison is secondary — the real win is that tang's derivatives are exact to machine precision. Finite differences require careful step-size tuning (too large → truncation error, too small → cancellation error) and break down for stiff systems. With tang, you just change the type parameter.

The LU solve benchmark highlights a capability nalgebra cannot match: because tang's decompositions are generic over Scalar, Lu::<Dual<f64>> gives you derivatives of the solution through the linear solve for free.

tang's dense LA is pure generic Rust (works with Dual<f64>, any Scalar impl). nalgebra dispatches to optimized BLAS/LAPACK-style routines for f64. For matrix products the gap is largely closed by tang-la::gemm; for decompositions it remains. On macOS, --features accelerate hands f32/f64 GEMM to Apple's AMX.

Matmul is dispatch-bound at small sizes (constant ~124µs for 16-128). The training step includes forward, loss, backward, and Adam update for a 3-layer network.

A character-level text generator trained on physics haikus. Demonstrates the full tang-train pipeline — dataset construction, sequential model, cross-entropy loss, Adam optimizer, and text generation.

cargo run --example quantum_poet -p tang-train

=== The Quantum Poet ===

corpus: 1491 chars, 1483 training samples, 8 parameters window
model: 21534 parameters

training...
  epoch   1: loss = 2.9453
  epoch  20: loss = 0.0916
  epoch 200: loss = 0.0207

--- seed: "quantum " ---
quantum fields vibrate below,
dimensions curl up and hide,
theory seeks the truth...

~21K parameters, trains in seconds on CPU. See crates/tang-train/examples/quantum_poet.rs.

cargo test --workspace
cargo test --workspace --all-features
cargo bench -p tang-bench

MIT