lattice-inference 0.2.2

#[cfg(not(target_os = "macos"))]
use super::simd::simd_config;

#[cfg(all(not(target_os = "macos"), target_arch = "aarch64"))]
use super::arch_kernels::matmul_neon;
#[cfg(all(not(target_os = "macos"), target_arch = "x86_64"))]
use super::arch_kernels::{matmul_avx2, matmul_avx512};
#[cfg(target_os = "macos")]
use super::blas::{accelerate_matmul, accelerate_matmul_bt};
#[cfg(not(target_os = "macos"))]
use super::tiled::matmul_bt_tiled;

/// **Unstable**: general matmul C = A*B; dispatches to platform BLAS or SIMD fallback.
///
/// General matrix multiplication: C = A * B.
pub fn matmul(a: &[f32], b: &[f32], m: usize, k: usize, n: usize) -> Vec<f32> {
    let mut c = vec![0.0f32; m * n];
    matmul_into(a, b, &mut c, m, k, n);
    c
}

/// **Unstable**: matmul into pre-allocated buffer; dispatch logic may change.
///
/// Matrix multiply into a pre-allocated output buffer.
pub fn matmul_into(a: &[f32], b: &[f32], c: &mut [f32], m: usize, k: usize, n: usize) {
    debug_assert_eq!(a.len(), m * k);
    debug_assert_eq!(b.len(), k * n);
    debug_assert_eq!(c.len(), m * n);

    // GPU dispatch is NOT in this hot path — per-call buffer creation is too slow.
    // GPU acceleration requires the full forward pass to run on-device.
    // See gpu_gemm.rs for standalone GPU GEMM (used in benchmarks).

    #[cfg(target_os = "macos")]
    {
        accelerate_matmul(a, b, c, m, n, k);
    }

    #[cfg(not(target_os = "macos"))]
    matmul_scalar(a, b, c, m, k, n);
}

/// **Unstable**: matmul C = A @ B^T; primary inference kernel, dispatch strategy evolving.
///
/// Matrix multiply with transposed B: C = A @ B^T.
pub fn matmul_bt(a: &[f32], b: &[f32], c: &mut [f32], m: usize, k: usize, n: usize) {
    debug_assert_eq!(a.len(), m * k);
    debug_assert_eq!(b.len(), n * k);
    debug_assert_eq!(c.len(), m * n);

    // CPU path only — Accelerate AMX on macOS, SIMD/scalar elsewhere.
    #[cfg(target_os = "macos")]
    {
        accelerate_matmul_bt(a, b, c, m, n, k);
    }

    // Non-macOS fallback: hand-written SIMD with tiling for large matrices.
    #[cfg(not(target_os = "macos"))]
    {
        // Use cache-blocked (tiled) path for large matrices where blocking pays off.
        // Two conditions must be met:
        //   1. Total work > 1M elements (below this, overhead dominates).
        //   2. K >= 128 (the shared dimension must be large enough that B-rows don't fit
        //      in L1 cache naturally). When K is small (e.g. 32), each B-row is only
        //      128 bytes and fits in L1 without tiling. Tiling would only change the
        //      accumulation order and introduce unnecessary numerical differences.
        let total_work = (m as u64) * (n as u64) * (k as u64);
        if total_work >= 1024 * 1024 && k >= super::tiled::TILE_K {
            matmul_bt_tiled(a, b, c, m, k, n);
            return;
        }

        let config = simd_config();

        #[cfg(target_arch = "x86_64")]
        {
            if config.avx512f_enabled && config.fma_enabled {
                // SAFETY: The runtime feature checks above guarantee AVX-512F+FMA support.
                unsafe {
                    matmul_avx512(a, b, c, m, k, n);
                    return;
                }
            }
            if config.avx2_enabled && config.fma_enabled {
                // SAFETY: The runtime feature checks above guarantee AVX2+FMA support.
                unsafe {
                    matmul_avx2(a, b, c, m, k, n);
                    return;
                }
            }
        }

        #[cfg(target_arch = "aarch64")]
        {
            if config.neon_enabled {
                // SAFETY: NEON is available on aarch64 and the runtime gate ensures this path.
                unsafe {
                    matmul_neon(a, b, c, m, k, n);
                    return;
                }
            }
        }

        matmul_bt_scalar(a, b, c, m, k, n);
    }
}

/// **Unstable**: scalar matmul reference; used for non-SIMD targets and testing.
///
/// Scalar reference implementation of A * B.
pub fn matmul_scalar(a: &[f32], b: &[f32], c: &mut [f32], m: usize, k: usize, n: usize) {
    c.fill(0.0);

    for i in 0..m {
        for p in 0..k {
            let a_val = a[i * k + p];
            let b_row = &b[p * n..(p + 1) * n];
            let c_row = &mut c[i * n..(i + 1) * n];
            for j in 0..n {
                c_row[j] += a_val * b_row[j];
            }
        }
    }
}

#[cfg_attr(target_os = "macos", allow(dead_code))]
pub fn matmul_bt_scalar(a: &[f32], b: &[f32], c: &mut [f32], m: usize, k: usize, n: usize) {
    for i in 0..m {
        let a_row = &a[i * k..(i + 1) * k];
        let c_row = &mut c[i * n..(i + 1) * n];
        for j in 0..n {
            let b_row = &b[j * k..(j + 1) * k];
            let mut sum = 0.0f32;
            for p in 0..k {
                sum += a_row[p] * b_row[p];
            }
            c_row[j] = sum;
        }
    }
}