Crate lak 

Linear algebra kernels.

LAK is a personal project. Its guiding question is whether fully-safe Rust and contiguous-memory-only BLAS routines can stay minimal and elegant without sacrificing much performance. Benchmarks can be found at https://devald.dev/notes/linalg-kernels/lak_8.pdf

LAK provides small lightweight BLAS-like routines over contiguous Rust slices. Matrices are stored column-major.

The main API is organized by BLAS level:

• l1 - vector-vector routines like l1::dot() and l1::axpy()
• l2 - matrix-vector routines like l2::gemv() and l2::trsv()
• l3 - matrix-matrix routines like l3::gemm()

Currently, l3::gemm() is the only level-3 routine implemented. LAK only accepts real f32/f64 scalars.

GEMM also provides direct f32 l3::sgemm() and f64 l3::dgemm() for maximum performance. Level-1 and level-2 routines are all generic.

Example:

use lak::l3::gemm;
use lak::types::{MatMut, MatRef, Transpose};

// column-major 2 x 3 matrix:
// [1 3 5]
// [2 4 6]
let a = [1.0, 2.0, 3.0, 4.0, 5.0, 6.0];

// column-major 3 x 2 matrix:
// [ 7 10]
// [ 8 11]
// [ 9 12]
let b = [7.0, 8.0, 9.0, 10.0, 11.0, 12.0];

let mut c = [0.0, 0.0, 0.0, 0.0];

let alpha = 1.0;
let beta = 0.0;

let a = MatRef::new(&a, (2, 3));
let b = MatRef::new(&b, (3, 2));
let mut c = MatMut::new(&mut c, (2, 2));
 
// c.reborrow() used to allow c.as_slice() afterwards. 
gemm(
    Transpose::NoTranspose,
    Transpose::NoTranspose,
    alpha,
    beta,
    a,
    b,
    c.reborrow(),
);

// C = A * B 
// [ 76 103] 
// [100 136] 
assert_eq!(c.as_slice(), &[76.0, 100.0, 103.0, 136.0]);

Data is passed through view types:

• types::VecRef and types::VecMut for vectors
• types::MatRef and types::MatMut for column-major matrices

The blas module provides unsafe BLAS-shaped LP64 and ILP64 wrapper functions. These wrappers keep the historical BLAS argument order, but LAK only accepts contiguous vectors and matrices:

• vector increments must be 1
• matrix leading dimensions must be equal to the number of rows.

This crate currently uses rustc 1.94.0-nightly for portable_simd.

Informal notes from writing LAK can be found at https://devald.dev.

Modules

blas

fused

l1

l2

l3

traits

types

Macros

assert_length_eq

asserts two VecRef/VecMut have equal length buffers

assert_length_eq_n_cols

asserts the length of a VecRef/VecMut buffer equals the number of cols in a MatRef/MatMut

assert_length_eq_n_rows

asserts the length of a VecRef/VecMut buffer equals the number of rows in a MatRef/MatMut