Struct Table2dU8xU8 

pub struct Table2dU8xU8 { /* private fields */ }

A 2D SIMD lookup table for u8 × u8 coordinates, supporting up to 64K entries.

This table stores data in row-major order and uses SIMD gather operations for efficient parallel lookups. Each lookup takes a row index (0..num_rows) and column index (0..num_cols), both as u8, and returns the corresponding value.

Index Calculation

For row r and column c, the flat index is: index = r * num_cols + c

Since row and column are both u8 (max 255), and num_cols is at most 256, the maximum index is 255 * 256 + 255 = 65535, which fits in u16.

Example

// Create a 16x16 multiplication table
let mut data = vec![0u8; 256];
for r in 0..16u8 {
    for c in 0..16u8 {
        data[(r as usize) * 16 + (c as usize)] = r.wrapping_mul(c);
    }
}
let table = Table2dU8xU8::from_flat(&data, 16);

// Look up multiple (row, col) pairs in parallel
let rows = u8x16::from([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]);
let cols = u8x16::splat(5);  // All looking up column 5
let result = table.lookup_one(rows, cols);
// result[i] = i * 5

Implementations

impl Table2dU8xU8

pub fn from_flat(data: &[u8], num_cols: usize) -> Self

Create a 2D table from a flat slice with the given number of columns.

The data is stored in row-major order: data[row * num_cols + col].

Arguments

• data: Flat slice of values, length must be num_rows * num_cols
• num_cols: Number of columns per row (1..=256)

Panics

• Panics if num_cols is 0 or greater than 256
• Panics if data.len() is not a multiple of num_cols
• Panics if data.len() > 65536

pub fn from_2d(matrix: &[&[u8]]) -> Self

Create a 2D table from a 2D matrix (Vec of rows).

All rows must have the same length.

Panics

• Panics if the matrix is empty
• Panics if rows have different lengths
• Panics if total size exceeds 65536

pub fn num_cols(&self) -> usize

Returns the number of columns per row.

pub fn num_rows(&self) -> usize

Returns the number of rows in the table.

pub fn len(&self) -> usize

Returns the total number of entries in the table.

pub fn is_empty(&self) -> bool

Returns true if the table is empty.

pub fn lookup_one(&self, rows: u8x16, cols: u8x16) -> u8x16

Look up 16 values in parallel using (row, col) coordinates.

Computes result[i] = table[rows[i]][cols[i]] for all 16 lanes.

Arguments

• rows: Row indices (0..num_rows) for each of the 16 lanes
• cols: Column indices (0..num_cols) for each of the 16 lanes

Safety

In debug mode, asserts that all indices are in bounds. In release mode, out-of-bounds access is undefined behavior.

pub fn get(&self, row: u8, col: u8) -> u8

Scalar lookup for a single (row, col) coordinate.

Panics

Panics if row or col is out of bounds.

Trait Implementations

impl Clone for Table2dU8xU8

fn clone(&self) -> Table2dU8xU8

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Table2dU8xU8

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Table2dU8xU8

fn default() -> Table2dU8xU8

Returns the “default value” for a type.