C++20 header-only linear algebra library for mixed-precision algorithm design and optimization.

MTL5 is a modernized successor to MTL4, preserving the proven architecture for custom number types (posits, LNS, etc.) while leveraging C++20 features for cleaner, safer, and more maintainable code.

• Header-only — no linking required
• C++20 concepts — clear constraints replacing SFINAE/enable_if
• Zero Boost dependency — pure C++20 standard library
• Expression templates — lazy evaluation with CRTP
• Mixed-precision support — designed for custom arithmetic types
• Dense & sparse — CSR/CSC, COO, ELLPACK, dense row/column-major
• ITL included — Krylov solvers (CG, BiCGSTAB, GMRES, IDR(s), ...) and preconditioners
• Type-safe math — math::zero<T>() and math::one<T>() for generic algorithms

• CMake 3.22+
• C++20 compiler (GCC 11+, Clang 14+, MSVC 2022+)
• Catch2 v3 (fetched automatically for tests)

# Clone
git clone https://github.com/stillwater-sc/mtl5.git
cd mtl5

# Build (uses dev preset: Debug, tests ON)
cmake --preset dev
cmake --build build -j$(nproc)

# Run tests
ctest --test-dir build

# Run example
./build/examples/hello_mtl5

include/mtl/
├── concepts/       # C++20 concepts (Scalar, Matrix, Vector, ...)
├── tag/            # Compile-time tags (orientation, sparsity, ...)
├── traits/         # Type traits and metafunctions
├── math/           # Algebraic identities (zero, one)
├── detail/         # Internal implementation
├── mat/            # Matrix types, expressions, views
├── vec/            # Vector types and expressions
├── operation/      # Free-function operations (dot, norms, LU, QR, ...)
├── functor/        # Scalar and typed functors
├── recursion/      # Block-recursive infrastructure
├── io/             # I/O (Matrix Market)
├── itl/            # Iterative solvers and preconditioners
└── interface/      # Optional BLAS/LAPACK bindings

cmake --preset release
cmake --build build-release
cmake --install build-release --prefix /usr/local

Then in your project:

find_package(MTL5 REQUIRED)
target_link_libraries(myapp PRIVATE MTL5::mtl5)

MIT License — see LICENSE.

MTL5 builds on the foundational work of MTL4 by Peter Gottschling and the Simunova team.