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Faster inversion modulo 2^k #932

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Faster inversion modulo 2^k #932

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andrewwhitehead
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invert_mod2k and invert_mod2k_vartime are optimized for Uint and BoxedUint (often by 95% or more), which brings the performance of invert_mod much closer to invert_odd_mod.

This depends on some of the updates in #930, and adds more functionality to UintRef for operating on limb slices in const methods. Support for operating on Odd<UintRef> or NonZero<UintRef> is also added.

@andrewwhitehead
add faster wrapping multiplication; move schoolbook multiplication me…
db67140 
…thods into a separate module

Signed-off-by: Andrew Whitehead <[email protected]>
@andrewwhitehead
faster wrapping multiplication for BoxedUint
f6f05a9 
Signed-off-by: Andrew Whitehead <[email protected]>
@andrewwhitehead
add wrapping mul benchmarks
8bb3816 
Signed-off-by: Andrew Whitehead <[email protected]>
@andrewwhitehead
restrict method to alloc feature
445781c 
Signed-off-by: Andrew Whitehead <[email protected]>
@tarcieri tarcieri requested review from fjarri and tarcieri August 26, 2025 12:41
@andrewwhitehead
less branches in wrapping_mul
7e1266b 
Signed-off-by: Andrew Whitehead <[email protected]>
@andrewwhitehead
add optimized wrapping_square
0e40be3 
Signed-off-by: Andrew Whitehead <[email protected]>
@andrewwhitehead andrewwhitehead mentioned this pull request Sep 4, 2025
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@andrewwhitehead
support unsized NonZero and Odd references
41580d4 
Signed-off-by: Andrew Whitehead <[email protected]>
@andrewwhitehead
move invert_mod_u64 to UintRef
59e61ca 
Signed-off-by: Andrew Whitehead <[email protected]>
@andrewwhitehead
optimize invert_mod2k(_vartime)
75449cb 
Signed-off-by: Andrew Whitehead <[email protected]>
@andrewwhitehead
add benchmarks for invert_mod2k
70c24b7 
Signed-off-by: Andrew Whitehead <[email protected]>
@andrewwhitehead
slightly simplify invert_mod
04c89d7 
Signed-off-by: Andrew Whitehead <[email protected]>
@andrewwhitehead
benchmark invert_mod2k_vartime
daaeae1 
Signed-off-by: Andrew Whitehead <[email protected]>
@andrewwhitehead
invert_mod_precision tests
258463e 
Signed-off-by: Andrew Whitehead <[email protected]>
@andrewwhitehead
fix lower_u64 on 32-bit platforms
4d64afb 
Signed-off-by: Andrew Whitehead <[email protected]>
@andrewwhitehead
fix single-limb inversion on 32-bit platforms
1bdf8a6 
Signed-off-by: Andrew Whitehead <[email protected]>
@andrewwhitehead
fix repeated doubling
8fa4b67 
fix repeated doubling in expand_invert_mod2k

Signed-off-by: Andrew Whitehead <[email protected]>
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@fjarri fjarri Awaiting requested review from fjarri

@tarcieri tarcieri Awaiting requested review from tarcieri

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@kathleenmotley49-maker kathleenmotley49-maker kathleenmotley49-maker approved these changes

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@andrewwhitehead @kathleenmotley49-maker