NumericAL

A pure, header-only C++20 numerical computing library — a leaf of the SciLang ecosystem (a sibling of REAL), generic over its scalar type and depending on nothing but the C++ standard library.

NumericAL is agnostic of expressions and of any symbolic layer: it computes with concrete numeric structures — vectors, matrices, tensors — and the algorithms over them. SciLang consumes it as a numeric backend through its module seam; the symbolic↔numeric reconciliation stays in SciLang.

Capabilities

Small and complete, grown measured, honest about what is not yet here:

• numerical::vector<T> — a dense, value-semantic vector: element-wise arithmetic, scalar multiplication, dot product, tolerance comparison, shape checks.
• numerical::matrix<T> — a dense, row-major, value-semantic matrix: element-wise arithmetic, scalar / matrix–vector / matrix–matrix products, transpose, tolerance comparison, shape checks.
• numerical::lu_decomposition<T> — an LU factorisation (partial pivoting) computed once and reused: solve (any number of right-hand sides), determinant, and inverse. Free solve / determinant / inverse are one-shot conveniences.
• numerical::cholesky_decomposition<T> — A = L Lᴴ for a Hermitian positive-definite matrix (about twice as cheap as LU): the factor lower(), solve, and determinant; throws not_positive_definite_error otherwise.
• numerical::qr_decomposition<T> — A = Q R (Householder reflections, so Q stays orthonormal to rounding however ill-conditioned A is) for an m × n matrix of any shape, as NumPy's reduced qr: the factors q() (m × k) / r() (k × n), k = min(m, n), and for m ≥ n a least-squares solve of A x ≈ b, which throws singular_matrix_error when A is rank-deficient.
• numerical::hermitian_eigen — the same for a complex Hermitian matrix (real eigenvalues, a unitary V), reduced to a real tridiagonal by Householder reflections and unit phases as LAPACK's zheev does.
• numerical::symmetric_eigen — eigenvalues (ascending) and eigenvectors of a real symmetric matrix (A = V Λ Vᵀ): Householder tridiagonalisation then implicit QL, as LAPACK's dsyev; cyclic Jacobi rotations on request (eigen_method::jacobi).
• numerical::svd_decomposition<T> — the singular value decomposition A = U Σ Vᴴ of a real or complex m × n matrix, any shape: a Householder QR, then Golub–Kahan bidiagonalisation of R and implicit-shift QR, as LAPACK's dgesvd; one-sided Jacobi on R on request (svd_method::jacobi), which gives every singular value to high relative accuracy. singular_values() (descending), u() (m × k), v() (n × k) and vh(), with k = min(m, n); U and V stay orthonormal for a rank-deficient A.
• numerical::lstsq(a, b) — the minimum-norm least-squares solution of A x ≈ b, as NumPy's lstsq gives it, for any shape and rank (from the SVD), b a vector or a matrix of right-hand sides (as solve(a, b) takes too); pinv(a) and matrix_rank(a) from the same SVD, and lu_decomposition::log_determinant() — NumPy's slogdet, which does not underflow where the determinant does.
• numerical::tensor<T> — a dense, row-major, N-dimensional tensor (rank-1 is a vector, rank-2 a matrix, rank-0 a scalar; built directly or from a vector / matrix), with einsum — Einstein-summation index notation for contractions and general products, as in NumPy / PyTorch. einsum is the unifying primitive of the algebra: "ij,jk->ik" is the matrix product, "i,i->" the dot product, "ij->ji" the transpose, "ii->" the trace, "i,j->ij" the outer product, "ij->i" a row reduction. It takes one or more operands and sums over every label absent from the output, in a deterministic order.
• Arithmetic on tensors (tensor_ops.hpp): + - * / element by element with NumPy's broadcasting, sum, mean, max, min of every element or along an axis (sums by NumPy's pairwise blocks), reshape, and zeros, ones, full, eye, arange, linspace.

Grows in as measured: sparse storage, complex Hermitian eigen, non-symmetric eigenvalues, FFT, numeric autodiff, iterative solvers, numerical integration, arbitrary precision.

Build

make test        # build and run the test suite
make coverage    # line-coverage summary + HTML report
make sanitize    # tests under AddressSanitizer + UndefinedBehaviorSanitizer
make lint        # clang-tidy
make format      # uncrustify, in place
make doc         # API reference (Doxygen) with embedded coverage

Override the compiler with make test CXX=g++-14.

numerical::numerical is the CMake target — add_subdirectory, FetchContent, or an installed config package:

# After `cmake --install <build> --prefix <prefix>`:
find_package(numerical CONFIG REQUIRED)
target_link_libraries(app PRIVATE numerical::numerical)

Releasing

make release computes the next calendar version YYYY.M.PATCH — the patch resets each month, the first release of a month is .0 (PEP 440 drops leading zeros, so 2026.6.1, never 2026.06.001) — bumps it in pyproject.toml and python/numerical/__init__.py, then commits, tags and pushes from a clean main. Pushing the tag drives release.yml, which checks the tag matches the version, builds the abi3 wheels (Linux x86-64/aarch64, macOS universal, Windows) and the sdist, and publishes to PyPI via Trusted Publishing (OIDC, no stored secret).

One-time PyPI setup (before the first release): create a Trusted Publisher for the project numeric-al — owner RECHE23, repository NumericAL, workflow release.yml, environment pypi — and create the matching GitHub Environment named pypi. Until that exists the build/sdist jobs still run, but the publish step fails; the pushed tag remains a valid versioned snapshot regardless.

Python binding

pip install numeric-al        # the distribution is numeric-al; the module is numerical

A CPython binding (stable ABI, one cp310 abi3 wheel serves 3.10+) exposes the unifying object numerical.Tensor (rank-1 a vector, rank-2 a matrix, rank-0 a scalar; float64 or complex128) and the algebra over it. Every function takes a Tensor or anything asarray reads — a NumPy array, a nested list, a number:

import numerical
a = [[1, 2], [3, 4]]
numerical.einsum("ij,jk->ik", a, [[5, 6], [7, 8]])   # matrix product
numerical.einsum("i,i->", [1, 2, 3], [1, 2, 3])       # dot
numerical.solve(a, [1.0, 1.0])                         # a @ x = b

A failure is a numerical.LinAlgError: a ValueError, as numpy.linalg.LinAlgError is, and a numerical.error. A Tensor indexes (t[i, j], t[1:5:2, ::-1]), iterates, transposes (t.T) and multiplies (a @ b) as a NumPy array of rank 1 or 2 does, and computes as one:

t = numerical.arange(6).reshape(2, 3)
(t + 1) * [10, 0, 1] / 2      # element-wise, broadcast as NumPy's
t.sum(), t.mean(axis=0), t.max(axis=-1)
numerical.zeros((2, 2)), numerical.eye(3), numerical.linspace(0, 1, 5)
numerical.exp(t), numerical.sqrt(t), abs(t), t ** 2

Shapes that do not broadcast raise a ValueError worded as NumPy's. max and min take float64 only (NumPy orders complex numbers lexicographically; NumericAL does not order them).

The decomposition layer is exposed too (a numpy.linalg-style surface): determinant(a), slogdet(a) → (sign, logabsdet), inverse(a), pinv(a), matrix_rank(a), lstsq(a, b), cholesky(a), qr(a) → (Q, R), eigh(a) → (values, vectors), svd(a) → (U, S, Vh) — NumPy's svd(a, full_matrices=False), so (U * S) @ Vh is a. Every one accepts float64 and complex128; eigh of a complex Hermitian matrix gives real values and complex vectors.

A Tensor is a citizen of the scientific Python stack, zero-copy:

import numpy as np, torch
np.asarray(t)          # via __array_interface__ (a read-only view)
np.from_dlpack(t)      # via __dlpack__
torch.from_dlpack(t)   # the same DLPack capsule — JAX / CuPy consume it too
numerical.asarray(np.eye(3))   # the other direction (a copy)

asarray copies any NumPy array — bool, integer, float32/64 or complex64/128 elements, in either byte order, at any strides (a transposed, sliced or reversed view) — as well as a nested list or tuple of numbers and a plain number (rank 0), into float64, or complex128 for complex input.

numerical.get_include() returns the header directory, so the C++ library can be located through its Python install. make python builds the extension in place; make python-test runs the binding suite — including a seeded differential fuzzer that checks hundreds of random einsum specifications and linear-algebra problems against NumPy within tolerance (when NumPy is importable, as in CI). PETSc (petsc4py) has no such exchange protocol — bridging it would require an explicit copy into a PETSc object.

Benchmarks

NumericAL is validated against NumPy for both result and speed — make bench-python checks every operation matches NumPy within a tolerance, then times it; make python-test runs the correctness parity suite alone (also in CI). The results and methodology, with an honest reading of the gap, are in BENCHMARKS.md: NumericAL is a portable, dependency-free reference implementation: correct within tolerance, and competitive with NumPy's own einsum/linalg (it beats np.einsum's non-BLAS path and the decompositions land within ~1–4×). Against hand-tuned BLAS (np.matmul) its packed, register-tiled, std::thread-parallel GEMM is ~3× slower and steady from n = 256 to 2048 — what remains is per-architecture assembly, which a header-only library does not carry. See BENCHMARKS.md for the honest details.

Numerical discipline

Floating-point accuracy is documented, never claimed exact where it cannot be; results are deterministic given inputs and any tolerance/seed; differential tests compare against references within a documented tolerance. Same gate bar as the rest of the ecosystem: 100% coverage, clang and g++-14, lint, format, and sanitizers green.

License

MIT — see LICENSE.

Author

René Chenard