randlapack-bindings

MATLAB, and eventually Python, bindings for RandLAPACK.

Scope (v0)

Proof-of-concept binding for a single driver, BQRRP (randomized blocked QR with column pivoting), in single and double precision, real matrices, column-major. More drivers as their C++ APIs stabilize. Python next.

Requirements

• CMake 3.20+, C++20 compiler
• RandLAPACK installed (with the pre-bindings-cleanup work or later) — point RandLAPACK_DIR at its lib/cmake/RandLAPACK directory
• MATLAB R2018a+ on a platform matching your C++ toolchain (Linux MATLAB for .mexa64, Windows MATLAB for .mexw64)

Build

cmake -S . -B build \
    -DRandLAPACK_DIR=/path/to/RandLAPACK-install/lib/cmake/RandLAPACK \
    -DMatlab_ROOT_DIR=/path/to/MATLAB
cmake --build build -j

If MATLAB is not found, MEX targets are skipped with a clear warning; the .m files still ship and can be used once the MEX is built. On success, matlab/+randlapack/private/bqrrp_mex.<ext> is in place.

Usage

addpath('/path/to/randlapack-bindings/matlab')

A = randn(2000, 200);
[Q, R, J] = randlapack.bqrrp(A);
err = norm(A(:, J) - Q*R, 'fro') / norm(A, 'fro');

Two output modes, chosen by a trailing string (qr-style):

[Q, R, J]       = randlapack.bqrrp(A, 'explicit')  % default; matches qr(A, 'vector')
[A_out, tau, J] = randlapack.bqrrp(A, 'implicit')  % GEQP3-format; skips Q materialization

Run help randlapack.bqrrp for the full signature, including the optional b_sz, d_factor, and RNG state arguments.

Runtime notes

On Linux MATLAB R2026a + Ubuntu 24.04 (and similar new-glibc hosts), MATLAB ships an older libstdc++.so.6 than your compiler's. MEX files built against the system libstdc++ fail at load with version GLIBCXX_3.4.32 not found. Workaround:

LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libstdc++.so.6 matlab

Alias it in your shell profile to make it transparent. Not needed on macOS or older Ubuntu hosts.

Conventions

• J is 1-based, matching MATLAB. BQRRP stores 1-based pivots natively; no conversion in the MEX layer.
• RNG state is Philox4x32: state.counter is uint32[4], state.key is uint32[2]. Omit it (defaults to seed 0) or pass a scalar uint32 seed.