data-beans 0.7.3

#[cfg(feature = "ndarray")]
use ndarray::prelude::*;
use rustc_hash::FxHashMap as HashMap;

use super::DMatrix;

pub fn build_name2index_map(_names: &[Box<str>]) -> HashMap<Box<str>, usize> {
    _names
        .iter()
        .enumerate()
        .map(|(r, name)| (name.clone(), r))
        .collect()
}

pub fn take_subset_indices_names(
    new_indices: &[usize],
    ntot: usize,
    old_names: Vec<Box<str>>,
) -> (HashMap<u64, u64>, Vec<Box<str>>) {
    let mut old2new: HashMap<u64, u64> = Default::default();
    let mut new2old = vec![];
    debug_assert!(ntot == old_names.len());
    let mut k = 0_u64;
    for idx in new_indices.iter() {
        if *idx < ntot {
            old2new.insert(*idx as u64, k);
            new2old.push(*idx);
            k += 1;
        }
    }

    let new_names = new2old
        .iter()
        .map(|&i| old_names[i].clone())
        .collect::<Vec<Box<str>>>();

    (old2new, new_names)
}

pub fn take_subset_indices_names_if_needed(
    new_indices: Option<&Vec<usize>>,
    ntot: Option<usize>,
    old_names: Vec<Box<str>>,
) -> (HashMap<u64, u64>, Vec<Box<str>>) {
    let ntot = ntot.unwrap_or(old_names.len());
    if let Some(new_indices) = new_indices {
        take_subset_indices_names(new_indices, ntot, old_names)
    } else {
        let names = old_names;
        let identity = (0..(ntot as u64))
            .zip(0..(ntot as u64))
            .collect::<HashMap<u64, u64>>();
        (identity, names)
    }
}

#[cfg(feature = "ndarray")]
pub fn ndarray_to_triplets(array: &Array2<f32>) -> Vec<(u64, u64, f32)> {
    let eps = 1e-6;
    array
        .indexed_iter()
        .filter(|(_, &elem)| elem.abs() > eps)
        .map(|((row, col), &value)| (row as u64, col as u64, value))
        .collect::<Vec<(u64, u64, f32)>>()
}

pub fn dmatrix_to_triplets(matrix: &DMatrix<f32>) -> Vec<(u64, u64, f32)> {
    let (nrow, _) = matrix.shape();
    let eps = 1e-6;
    matrix
        .iter() // column-major
        .enumerate()
        .filter(|(_, &elem)| elem.abs() > eps)
        .map(|(idx, &value)| {
            let row = idx % nrow;
            let col = idx / nrow;
            (row as u64, col as u64, value)
        })
        .collect::<Vec<(u64, u64, f32)>>()
}

/// Remove a backend at `path`, whether it is a file (`.h5`, `.zarr.zip`) or a
/// directory (`.zarr`). Nothing happens when the path does not exist.
pub fn remove_backend_path(path: &str) -> anyhow::Result<()> {
    let p = std::path::Path::new(path);
    if p.exists() {
        if p.is_file() {
            std::fs::remove_file(p)?;
        } else {
            std::fs::remove_dir_all(p)?;
        }
    }
    Ok(())
}

/// Whether a preload of `nnz` entries fits the budget.
///
/// Preloading costs 12 bytes per non-zero (a `u64` index and an `f32` value)
/// and no consumer ever releases it, so an unchecked preload at imaging scale
/// is an OOM order, not a request. The budget turns that into a logged skip:
/// every read path already handles the not-preloaded state, it is just slower.
///
/// The budget is half the memory available when the process first asks,
/// shared by every preload of the process (8 GiB when the system does not
/// say). `LEGUME_PRELOAD_BUDGET_BYTES` overrides it per preload, following the
/// `LEGUME_ZARR_CACHE_CAP` precedent for memory knobs.
pub fn preload_within_budget(nnz: usize, what: &str) -> bool {
    use std::sync::atomic::{AtomicUsize, Ordering};
    const BYTES_PER_NNZ: usize = 12;
    static RESERVED: AtomicUsize = AtomicUsize::new(0);

    let cost = nnz.saturating_mul(BYTES_PER_NNZ);
    if let Some(budget) = std::env::var("LEGUME_PRELOAD_BUDGET_BYTES")
        .ok()
        .and_then(|v| v.parse::<usize>().ok())
    {
        return fits_or_warn(cost, budget, nnz, what);
    }
    let budget = auto_preload_budget_bytes();
    let reserved = RESERVED.fetch_add(cost, Ordering::Relaxed);
    if fits_or_warn(reserved.saturating_add(cost), budget, nnz, what) {
        true
    } else {
        RESERVED.fetch_sub(cost, Ordering::Relaxed);
        false
    }
}

fn fits_or_warn(cost: usize, budget: usize, nnz: usize, what: &str) -> bool {
    if cost > budget {
        log::warn!(
            "skipping {what} preload of {nnz} nnz: {cost} bytes would exceed the \
             {budget}-byte budget (LEGUME_PRELOAD_BUDGET_BYTES to raise); reads stay on the \
             streaming path"
        );
        false
    } else {
        true
    }
}

/// Half the memory available at the first call, or 8 GiB when unknown.
fn auto_preload_budget_bytes() -> usize {
    static BUDGET: std::sync::OnceLock<usize> = std::sync::OnceLock::new();
    *BUDGET.get_or_init(|| {
        const FALLBACK_BYTES: usize = 8 << 30;
        let mut sys = sysinfo::System::new();
        sys.refresh_memory();
        match usize::try_from(sys.available_memory()) {
            Ok(avail) if avail > 0 => avail / 2,
            _ => FALLBACK_BYTES,
        }
    })
}

/// Whether loaders preload columns without being asked. On unless
/// `LEGUME_AUTO_PRELOAD` is `0`, `false` or `off`; the preload itself still
/// answers to [`preload_within_budget`], so data that does not fit in memory
/// stays on the streaming path.
#[allow(dead_code)] // called by library loaders; the bin has none
pub fn auto_preload_enabled() -> bool {
    !matches!(
        std::env::var("LEGUME_AUTO_PRELOAD").as_deref(),
        Ok("0") | Ok("false") | Ok("off")
    )
}

/// Bytes of `(u64, u64, f32)` triplets a streaming-write slab may hold, and the
/// padded size of one such triplet. One definition, because the two streaming
/// pipelines (the subset trait method and the handlers' column-selection
/// writer) each carried their own copy and two memory ceilings drift apart.
pub const SLAB_BUDGET_BYTES: usize = 256 << 20;
/// `(u64, u64, f32)` padded.
pub const TRIPLET_BYTES: usize = 24;