backends/openblas Tutorial

Before You Start

backends/openblas is native only. The current repository configuration searches OpenBLAS from:

• /opt/homebrew/opt/openblas/include
• /opt/homebrew/opt/openblas/lib
• /usr/include/x86_64-linux-gnu/openblas-pthread
• /usr/include/openblas
• /usr/lib/x86_64-linux-gnu/openblas-pthread
• /usr/lib/x86_64-linux-gnu

This covers the default Homebrew layout on macOS and the default Ubuntu OpenBLAS package layout. If OpenBLAS is not installed in one of those places, native build and test commands for this package will fail at compile or link time.

Construct A BlasMatrix

///|
test "construct BlasMatrix from a 2D array" {
  let matrix = @openblas.BlasMatrix::from_2d_array([
    [1.0F, 2.0F, 3.0F],
    [4.0F, 5.0F, 6.0F],
  ])
  inspect(matrix.row(), content="2")
  inspect(matrix.col(), content="3")
}

Use Float or Double. Those are the only scalar types that currently implement BLASInnerType.

Multiply Matrices Through OpenBLAS

///|
test "BlasMatrix multiplication uses the backend matmul path" {
  let left = @openblas.BlasMatrix::from_2d_array([
    [1.0, 2.0, 3.0],
    [4.0, 5.0, 6.0],
  ])
  let right = @openblas.BlasMatrix::from_2d_array([
    [7.0, 8.0],
    [9.0, 10.0],
    [11.0, 12.0],
  ])
  let product = left * right
  debug_inspect(product.to_2d_array(), content="[[58, 64], [139, 154]]")
}

Mul is the operation that goes through OpenBLAS GEMM. Dimension mismatch keeps the same semantics as the repository's other unchecked matrix multiplication paths: it aborts.

Convert Between BlasMatrix And The Default Immutable Dense Backend

///|
test "convert between OpenBLAS and default immutable dense backend" {
  let base = @default.ImmutableDenseMatrix::from_2d_array([
    [1.0F, 2.0F],
    [3.0F, 4.0F],
  ])
  let blas = @openblas.BlasMatrix::from_default(base)
  let round_trip = blas.to_default()
  debug_inspect(round_trip.inner().to_2d_array(), content="[[1, 2], [3, 4]]")
}

Equivalent conversion APIs also exist for the concrete immutable matrix type:

• BlasMatrix::from_immut
• BlasMatrix::to_immut

Minimal Native Test Flow

Use native commands when exercising this backend:

moon test src/backends/openblas --target native
moon test --target native

If you want to depend on this package from another MoonBit package, keep the same rule in mind: choose BlasMatrix explicitly and build for native.