Module arithmetic 

Arithmetic primitives for rANS.

This module provides:

• mul_hi_u64: High 64 bits of 64x64 multiply (equivalent to __umulh / Mul64Hi)
• compute_reciprocal: Reciprocal frequency preparation for fast division

The arithmetic here must match the Microsoft C++ implementation exactly.

Functions

compute_reciprocal_u32

Compute the fixed-point reciprocal frequency for a 32-bit state.

compute_reciprocal_u64

Compute the fixed-point reciprocal frequency for a 64-bit state.

fast_quotient_u32

fast_quotient_u64

Perform fast division by frequency using the reciprocal.

freq_one_reciprocal_u32

Compute the frequency-one reciprocal for 32-bit state.

freq_one_reciprocal_u64

Compute the frequency-one reciprocal for 64-bit state.

mul_hi_u64

Returns the high 64 bits of the 128-bit product of two 64-bit integers.

reciprocal_shift

Compute the reciprocal shift for a given frequency.