subtract_multiple()

void M2::ARingZZp::subtract_multiple ( elem & result, elem a, elem b ) const

inline

Definition at line 247 of file aring-zzp.hpp.

  {
    // we assume: a, b are NONZERO!!
    // result -= a*b
    
    // the change in code below mimics that of coeffrings.cpp which was 15-20% faster in
    // testing for some reason (in small characteristics).  The assembly generated is much more
    // clean than it was previously.
 
    //int ab = a + b;
    //if (ab > p1) ab -= p1;
    int ab = modulus_add(a,b,p1);
    //int n = exp_table[result] - exp_table[ab];
    //if (n < 0) n += p;
    int n = modulus_sub(exp_table[result],exp_table[ab],p);
    result = log_table[n];
  }

References exp_table, log_table, modulus_add(), modulus_sub(), p, p1, and result().