matten 0.46.0

A family-car multidimensional array (tensor) library for small numerical trials / PoCs.
Documentation 
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//! Visual shape and axis summary for a few core tensor operations.
//!
//! Run: cargo run --example 57_visual_shape_axis_summary
//!
//! This example prints short, deterministic summaries: inputs, operation,
//! output shape, and small output values. It is intentionally not a full
//! tutorial; the mdBook reference pages carry the larger diagrams.

use matten::Tensor;

/// Renders a tensor as an aligned rank-2 grid, a rank-1 row, or the rank-0
/// scalar, so Reshape's two blocks visibly *look* different instead of
/// printing two identical value lists (RFC-096, applying RFC-095's playground
/// fix here too). Uses core `Tensor`'s own `Display` (RFC-100) for the
/// values; this file only adds the `label` / `shape=` header line Display
/// deliberately does not print, since Display has no notion of a caller
/// label. Rank ≤ 2's header is separate from the grid because `Display`
/// itself omits shape for those ranks; rank > 2's `Display` already includes
/// `shape=... values=...` (RFC-100 §5.3), so only the label is prepended
/// there. Because this cannot be unit-tested — examples build as binaries,
/// so `#[test]` inside one never runs — every call site below asserts the
/// exact rendered block, padding included, before printing it.
fn render_block(label: &str, t: &Tensor) -> String {
    if t.shape().len() <= 2 {
        format!("{label:<16} shape={:?}\n{t}", t.shape())
    } else {
        format!("{label:<16} {t}")
    }
}

fn main() {
    let a = Tensor::new(vec![1.0, 2.0, 3.0, 4.0, 5.0, 6.0], &[2, 3]);
    let b = Tensor::new(vec![10.0, 20.0, 30.0], &[3]);

    println!("== Broadcasting ==");
    let input_a = render_block("input A", &a);
    assert_eq!(
        input_a,
        "input A          shape=[2, 3]\n1.0 2.0 3.0\n4.0 5.0 6.0"
    );
    println!("{input_a}");
    let input_b = render_block("input b", &b);
    assert_eq!(input_b, "input b          shape=[3]\n10.0 20.0 30.0");
    println!("{input_b}");
    let broadcast = &a + &b;
    let broadcast_block = render_block("A + b", &broadcast);
    assert_eq!(
        broadcast_block,
        "A + b            shape=[2, 3]\n11.0 22.0 33.0\n14.0 25.0 36.0"
    );
    println!("{broadcast_block}");
    println!("meaning         b repeats across rows");
    assert_eq!(broadcast.shape(), &[2, 3]);
    assert_eq!(broadcast.as_slice(), &[11.0, 22.0, 33.0, 14.0, 25.0, 36.0]);

    println!();
    println!("== Reshape ==");
    let reshaped = a.reshape(&[3, 2]);
    let reshape_input = render_block("[2, 3] input", &a);
    assert_eq!(
        reshape_input,
        "[2, 3] input     shape=[2, 3]\n1.0 2.0 3.0\n4.0 5.0 6.0"
    );
    println!("{reshape_input}");
    let reshape_view = render_block("[3, 2] view", &reshaped);
    assert_eq!(
        reshape_view,
        "[3, 2] view      shape=[3, 2]\n1.0 2.0\n3.0 4.0\n5.0 6.0"
    );
    println!("{reshape_view}");
    println!("meaning         row-major values stay in the same order");
    assert_eq!(reshaped.shape(), &[3, 2]);
    assert_eq!(reshaped.as_slice(), a.as_slice());

    println!();
    println!("== Axis reductions ==");
    let col_means = a.mean_axis(0);
    let row_means = a.mean_axis(1);
    println!(
        "mean_axis(0)    collapse rows, keep columns -> shape {:?}, values {:?}",
        col_means.shape(),
        col_means.as_slice()
    );
    println!(
        "mean_axis(1)    collapse columns, keep rows -> shape {:?}, values {:?}",
        row_means.shape(),
        row_means.as_slice()
    );
    assert_eq!(col_means.shape(), &[3]);
    assert_eq!(col_means.as_slice(), &[2.5, 3.5, 4.5]);
    assert_eq!(row_means.shape(), &[2]);
    assert_eq!(row_means.as_slice(), &[2.0, 5.0]);

    println!();
    println!("== Matrix multiplication ==");
    let left = Tensor::new(vec![1.0, 2.0, 3.0, 4.0, 5.0, 6.0], &[2, 3]);
    let right = Tensor::new(vec![1.0, 2.0, 3.0, 4.0, 5.0, 6.0], &[3, 2]);
    let product = left.matmul(&right);
    let left_block = render_block("left", &left);
    assert_eq!(
        left_block,
        "left             shape=[2, 3]\n1.0 2.0 3.0\n4.0 5.0 6.0"
    );
    println!("{left_block}");
    let right_block = render_block("right", &right);
    assert_eq!(
        right_block,
        "right            shape=[3, 2]\n1.0 2.0\n3.0 4.0\n5.0 6.0"
    );
    println!("{right_block}");
    let product_block = render_block("left.matmul", &product);
    assert_eq!(
        product_block,
        "left.matmul      shape=[2, 2]\n22.0 28.0\n49.0 64.0"
    );
    println!("{product_block}");
    println!("meaning         [2, 3] x [3, 2] -> [2, 2]");
    assert_eq!(product.shape(), &[2, 2]);
    assert_eq!(product.as_slice(), &[22.0, 28.0, 49.0, 64.0]);

    println!();
    println!("57_visual_shape_axis_summary: OK");
}