text: #include "reduce.h"
  
  #include "params.h"
  
  #include <stdint.h>
  /*************************************************
  * Name:        montgomery_reduce
  *
  * Description: Montgomery reduction; given a 32-bit integer a, computes
  *              16-bit integer congruent to a * R^-1 mod q,
  *              where R=2^16
  *
  * Arguments:   - int32_t a: input integer to be reduced; has to be in {-q2^15,...,q2^15-1}
  *
  * Returns:     integer in {-q+1,...,q-1} congruent to a * R^-1 modulo q.
  **************************************************/
  int16_t PQCLEAN_KYBER102490S_CLEAN_montgomery_reduce(int32_t a) {
      int32_t t;
      int16_t u;
  
      u = (int16_t)(a * (int64_t)QINV);
      t = (int32_t)u * KYBER_Q;
      t = a - t;
      t >>= 16;
      return (int16_t)t;
  }
  
  /*************************************************
  * Name:        barrett_reduce
  *
  * Description: Barrett reduction; given a 16-bit integer a, computes
  *              16-bit integer congruent to a mod q in {0,...,q}
  *
  * Arguments:   - int16_t a: input integer to be reduced
  *
  * Returns:     integer in {0,...,q} congruent to a modulo q.
  **************************************************/
  int16_t PQCLEAN_KYBER102490S_CLEAN_barrett_reduce(int16_t a) {
      int32_t t;
      const int32_t v = (1U << 26) / KYBER_Q + 1;
  
      t = v * a;
      t >>= 26;
      t *= KYBER_Q;
      return a - (int16_t)t;
  }
  
  /*************************************************
  * Name:        csubq
  *
  * Description: Conditionallly subtract q
  *
  * Arguments:   - int16_t a: input integer
  *
  * Returns:     a - q if a >= q, else a
  **************************************************/
  int16_t PQCLEAN_KYBER102490S_CLEAN_csubq(int16_t a) {
      a -= KYBER_Q;
      a += (a >> 15) & KYBER_Q;
      return a;
  }
  