Struct InvariantDivisor31 

pub struct InvariantDivisor31 { /* private fields */ }

Exact n / d for 0 <= n < 2^31 by one multu and a shift, for a divisor that is fixed across many dividends.

Granlund and Montgomery, “Division by invariant integers using multiplication” (1994), theorem 4.2 with N = 31: for l = ceil(log2 d) and m = floor(2^(31+l) / d) + 1, floor(m * n / 2^(31+l)) equals floor(n / d) for every n < 2^31, and m fits 32 bits. The R3000A’s div interlocks the pipeline for about 35 cycles and multu for about 12 (fewer for small operands), so a per-model depth-slot divide that ran once per drawn face pays for its new after a handful of faces.

Implementations

impl InvariantDivisor31

pub const fn new(divisor: u32) -> Self

Prepare divisor, which must be at least one. This is the 32-step software divide, so prepare once where the divisor is decided (a depth range, a table size), not per use.

pub fn divide(self, n: u32) -> u32

n / divisor for n < 2^31.

Trait Implementations

impl Clone for InvariantDivisor31

fn clone(&self) -> InvariantDivisor31

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for InvariantDivisor31

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

Formats the value using the given formatter.

impl PartialEq for InvariantDivisor31

fn eq(&self, other: &InvariantDivisor31) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for InvariantDivisor31

impl Eq for InvariantDivisor31

impl StructuralPartialEq for InvariantDivisor31