subduct1() [2/2]

ring_elem sagbi::subduct1 ( int numslots, const PolyRing * T, const PolyRing * S, ring_elem a, const RingMap * inclusionAmbient, const RingMap * fullSubstitution, const RingMap * substitutionInclusion, GBComputation * gbI, GBComputation * gbReductionIdeal )

static

Definition at line 71 of file sagbi.cpp.

{
    Nterm *f = a;
    ring_elem fr = f;
    MatrixConstructor matT(T->make_FreeModule(1), 1);
    MatrixConstructor matS(S->make_FreeModule(1), 1);
    bool breakFlag = false;
 
    (void) numslots;
    while ((f != nullptr) && (breakFlag == false))
    {
        // tensorRingg = S#"inclusionAmbient" liftg
        // tesnorRingg = gInT
        ring_elem gInT = S->eval(inclusionAmbient,fr,0);
 
        // This might be the wrong way to deal with this issue.
        // I don't know what to do, however.
        if(gInT != nullptr)
          {
              // tensorRingLTg = leadTerm tensorRingg
              // tensorRingLTg = LTgInT
              Nterm *LTgInT = gInT;
              LTgInT->next = nullptr;
        
            // h = tensorRingLTg % (inAIdeal)
            // h = h1
            matT.set_entry(0,0,LTgInT);
            Matrix *m = matT.to_matrix();
            const Matrix *n = gbReductionIdeal->matrix_remainder(m);
            ring_elem h1 = n->elem(0,0);
            delete m;
            delete n;
 
            ring_elem projectionh = T->eval(substitutionInclusion,h1,0);
            
            if(projectionh != nullptr)
            {
                // hSub = (S#"fullSubstitution" h) % I
                ring_elem hInS = T->eval(fullSubstitution,h1,0);
                matS.set_entry(0,0,hInS);
                Matrix *k = matS.to_matrix();
                const Matrix *l = gbI->matrix_remainder(k);
                ring_elem h1InS = l->elem(0,0);
                delete k;
                delete l;
                
                S->internal_subtract_to(fr,h1InS);
                f = fr;
            }
            else
                breakFlag = true;
          }
        else
            breakFlag = true;
    }
    
    return ring_elem(f);
}

References Matrix::elem(), PolyRing::eval(), PolyRing::internal_subtract_to(), Ring::make_FreeModule(), Matrix, GBComputation::matrix_remainder(), Nterm::next, MatrixConstructor::set_entry(), T, and MatrixConstructor::to_matrix().

Referenced by rawSubduction1(), and subduct1().