bitvector - some bugfixes and further implementations
This commit is contained in:
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9bceebdd29
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e42987061f
182
bitvector.cc
182
bitvector.cc
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@ -39,21 +39,48 @@ return s;
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}
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void bitvector::zero_padding() const
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{
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if(!modulo) return;
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bitvector *p = const_cast<bitvector *>(this);
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p->v[nn-1] &= (1ULL<<modulo)-1;
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}
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bitvector& bitvector::operator++()
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{
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copyonwrite();
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zero_padding();
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int i=0;
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while(i<nn) if(++v[i++]) break;
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return *this;
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}
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bitvector& bitvector::operator--()
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{
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copyonwrite();
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zero_padding();
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int i=0;
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while(i<nn) if(v[i++]--) break;
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return *this;
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}
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//implemented so that vectors of different length are considered different automatically
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bool bitvector::operator!=(const bitvector &rhs) const
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{
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if(nn!=rhs.nn || modulo!=rhs.modulo) return 1;
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if(v==rhs.v) return 0;
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if(!modulo) return memcmp(v,rhs.v,nn*sizeof(bitvector_block));
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if(memcmp(v,rhs.v,(nn-1)*sizeof(bitvector_block))) return 1;
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bitvector_block a=v[nn-1];
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bitvector_block b=rhs.v[nn-1];
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//zero out the irrelevant bits
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bitvector_block mask= ~((bitvector_block)0);
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mask <<=modulo;
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mask = ~mask;
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a&=mask; b&=mask;
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return a!=b;
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if(nn==rhs.nn && modulo==rhs.modulo && v==rhs.v) return false;
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zero_padding();
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rhs.zero_padding();
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int minnn=nn; if(rhs.nn<minnn) minnn=rhs.nn;
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int maxnn=nn; if(rhs.nn>maxnn) maxnn=rhs.nn;
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if(memcmp(v,rhs.v,minnn*sizeof(bitvector_block))) return true;
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if(minnn==maxnn) return false;
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if(nn==minnn) {for(int i=minnn; i<maxnn; ++i) if(rhs.v[i]) return true;}
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if(rhs.nn==minnn){for(int i=minnn; i<maxnn; ++i) if(v[i]) return true;}
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return false;
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}
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@ -97,6 +124,7 @@ bitvector bitvector::operator~() const
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{
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bitvector r((*this).size());
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for(int i=0; i<nn; ++i) r.v[i] = ~v[i];
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r.zero_padding();
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return r;
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}
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@ -197,12 +225,7 @@ void bitvector::randomize()
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{
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copyonwrite();
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for(int i=0; i<nn; ++i) v[i]=RANDINT64();
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//zero the excess bits
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if(modulo)
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{
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bitvector_block mask = (1ULL<<modulo)-1;
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v[nn-1] &= mask;
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}
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zero_padding();
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}
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@ -322,6 +345,7 @@ bitvector r(size());
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r.clear();
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bitvector tmp(*this);
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tmp.resize(size()+1,true);
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tmp.copyonwrite();
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int rd=rhs.degree();
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for(int i=0; i<=rd; ++i) //avoid making a working copy of rhs and shifting it
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{
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@ -358,7 +382,7 @@ while(!newr.is_zero())
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t=newt; newt=remainder;
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}
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if(r.degree()>0) laerror("field_inv: polynomial is not irreducible or input is its multiple");
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if(r.degree()>0) laerror("field_inv: polynomial is not irreducible or input is zero modulo the polynomial");
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if(!r[0]) laerror("zero in field_inv");
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return t;
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@ -368,12 +392,13 @@ return t;
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void bitvector::resize(const unsigned int n, bool preserve)
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{
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int old=size();
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if(preserve) zero_padding();
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int oldnn=nn;
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NRVec<bitvector_block>::resize((n+blockbits-1)/blockbits,preserve);
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modulo=n%blockbits;
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if(preserve) //clear newly allocated memory
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{
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for(int i=old; i<nn*blockbits; ++i) this->reset(i);
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for(int i=oldnn; i<nn; ++i) v[i]=0;
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}
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else clear();
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}
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@ -430,6 +455,7 @@ return big;
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//cf. Brent & Zimmermann ANZMC08t (2008) paper
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//
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bool bitvector::is_irreducible() const
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{
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bitvector tmp(size());
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@ -452,7 +478,8 @@ for(auto p=f.begin(); p!=f.end(); ++p)
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for(unsigned int j=0; j<dm; ++j) tmp = tmp.field_mult(tmp,*this);
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tmp.flip(1);
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bitvector g=tmp.gcd(*this);
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if(!g,is_one()) return false;
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//std::cout << "TEST tmp, ir, gcd, is_one "<<tmp<<" "<<*this<<" "<<g<<" : "<<g.is_one()<<std::endl;
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if(!g.is_one()) return false;
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}
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return true;
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}
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@ -508,6 +535,117 @@ if(dimensions)
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NRVec<bitvector_block>::put(fd,dimensions,transp);
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}
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static bitvector *tryme;
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static bool irfound;
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static int mynth;
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static void irfinder(int nones, int top)
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{
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if(irfound) return;
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if(nones==0) //terminate recursion
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{
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bool testit = tryme->is_irreducible();
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//std::cout <<"candidate = "<< *tryme<< " result = "<<testit<<std::endl;
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if(testit)
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{
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--mynth;
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if(!mynth) irfound=true;
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}
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return;
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}
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for(int i=nones; i<=top; ++i)
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{
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tryme->set(i);
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irfinder(nones-1,i-1);
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if(irfound) break;
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else tryme->reset(i);
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}
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}
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bitvector find_irreducible(int deg, int pop, int nth)
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{
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if(deg<=0) laerror("illegal degree in find_irreducible");
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if(deg==1) {bitvector r(2); r.set(1); r.reset(0); return r;}
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bitvector r(deg+1);
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if(pop== -1)
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{
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do {
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r.randomize();
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r.set(0);
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r.set(deg);
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if((r.population()&1)==0) r.flip(1+RANDINT32()%(deg-2));
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}
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while(!r.is_irreducible());
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return r;
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}
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if(pop<3 || (pop&1)==0) laerror("impossible population of irreducible polynomial requested");
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r.clear();
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r.set(0);
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r.set(deg);
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pop-=2;
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tryme= &r;
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irfound=false;
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mynth=nth;
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irfinder(pop,deg-1);
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if(!irfound) r.clear();
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return r;
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}
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bitvector bitvector::pow(unsigned int n) const
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{
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if(n==0) {bitvector r(size()); r.clear(); r.set(0); return r;}
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if(n==1) return *this;
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bitvector y,z;
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z= *this;
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while(!(n&1))
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{
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z = z*z;
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n >>= 1;
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}
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y=z;
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while((n >>= 1)/*!=0*/)
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{
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z = z*z;
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if(n&1) y *= z;
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}
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return y;
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}
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bitvector bitvector::field_pow(unsigned int n, const bitvector &ir) const
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{
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if(n==0) {bitvector r(size()); r.clear(); r.set(0); return r;}
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if(n==1) return *this;
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bitvector y,z;
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z= *this;
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while(!(n&1))
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{
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z = z.field_mult(z,ir);
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n >>= 1;
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}
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y=z;
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while((n >>= 1)/*!=0*/)
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{
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z = z.field_mult(z,ir);
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if(n&1) y = y.field_mult(z,ir);
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}
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return y;
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}
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//sqrt(x) is x^(2^(d-1))
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bitvector bitvector::field_sqrt(const bitvector &ir) const
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{
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int d=ir.degree();
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bitvector r(*this);
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for(int i=0; i<d-1; ++i)
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{
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r= r.field_mult(r,ir);
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}
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r.resize(d+1,true);
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return r;
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}
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21
bitvector.h
21
bitvector.h
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@ -43,7 +43,7 @@ private:
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unsigned int modulo;
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public:
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bitvector() : NRVec<bitvector_block>() {};
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explicit bitvector (const unsigned int n):NRVec<bitvector_block>((n+blockbits-1)/blockbits) {modulo=n%blockbits;};
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explicit bitvector (const unsigned int n):NRVec<bitvector_block>((n+blockbits-1)/blockbits) {modulo=n%blockbits; memset(v,0,nn*sizeof(bitvector_block));};
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bitvector (const bitvector_block a, const unsigned int n):NRVec<bitvector_block>(a,(n+blockbits-1)/blockbits) {modulo=n%blockbits;};
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bitvector(const bitvector &rhs) : NRVec<bitvector_block>(rhs) {modulo=rhs.modulo;};
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//operator= seems to be correctly synthetized by the compiler
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@ -63,10 +63,13 @@ public:
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const bool assign(const unsigned int i, const bool r) {if(r) set(i); else reset(i); return r;};
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void clear() {copyonwrite(true); memset(v,0,nn*sizeof(bitvector_block));};
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void fill() {memset(v,0xff,nn*sizeof(bitvector_block));};
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bool iszero() const {for(int i=0; i<nn; ++i) if(v[i]) return false; return true;};
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bool is_zero() const {return iszero();};
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bool is_one() const {if(v[0]!=1) return false; for(int i=1; i<nn; ++i) if(v[i]) return false; return true;};
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void zero_padding() const;
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bool is_zero() const {zero_padding(); for(int i=0; i<nn; ++i) if(v[i]) return false; return true;};
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bool is_one() const {zero_padding(); if(v[0]!=1) return false; for(int i=1; i<nn; ++i) if(v[i]) return false;return true;};
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bool iszero() const {return is_zero();};
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void randomize();
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bitvector& operator++();
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bitvector& operator--();
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bool operator!=(const bitvector &rhs) const;
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bool operator==(const bitvector &rhs) const {return !(*this != rhs);};
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bool operator>(const bitvector &rhs) const;
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@ -77,6 +80,9 @@ public:
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bitvector& operator&=(const bitvector &rhs);
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bitvector& operator|=(const bitvector &rhs);
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bitvector& operator^=(const bitvector &rhs);
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bitvector& operator&=(const bitvector_block rhs) {v[0]&=rhs; return *this;};
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bitvector& operator|=(const bitvector_block rhs) {v[0]|=rhs; return *this;};
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bitvector& operator^=(const bitvector_block rhs) {v[0]^=rhs; return *this;};
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bitvector& operator+=(const bitvector &rhs) {return (*this)^=rhs;}; //addition modulo 2
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bitvector& operator-=(const bitvector &rhs) {return (*this)^=rhs;}; //subtraction modulo 2
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bitvector operator&(const bitvector &rhs) const {return bitvector(*this) &= rhs;};
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@ -87,10 +93,13 @@ public:
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bitvector multiply(const bitvector &rhs, bool autoresize=true) const; //use autoresize=false only if you know it will not overflow!
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bitvector operator*(const bitvector &rhs) const {return multiply(rhs,true);} //multiplication of polynomials over GF(2) NOTE: naive algorithm, does not employ CLMUL nor fft-like approach, only for short vectors!!!
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bitvector& operator*=(const bitvector &rhs) {*this = (*this)*rhs; return *this;}
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bitvector pow(unsigned int n) const;
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bitvector field_mult(const bitvector &rhs, const bitvector &irpolynom) const; //multiplication in GF(2^n)
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bitvector field_inv(const bitvector &irpolynom) const; //multiplication in GF(2^n)
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bitvector field_div(const bitvector &rhs, const bitvector &irpolynom) const {return field_mult(rhs.field_inv(irpolynom),irpolynom);};
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bitvector field_composition(const bitvector &rhs, const bitvector &irpolynom) const;
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bitvector field_pow(unsigned int n, const bitvector &irpolynom) const;
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bitvector field_sqrt(const bitvector &irpolynom) const;
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bool is_irreducible() const; //test irreducibility of polynomial over GF2
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bitvector division(const bitvector &rhs, bitvector &remainder) const;
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bitvector operator/(const bitvector &rhs) const {bitvector rem(rhs.size()); return division(rhs,rem);};
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@ -99,7 +108,7 @@ public:
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bitvector lcm(const bitvector &rhs) const {return (*this)*rhs/this->gcd(rhs);};
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bitvector composition(const bitvector &rhs) const;
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unsigned int bitdiff(const bitvector &y) const; //number of differing bits (Hamming distance)
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unsigned int population(const unsigned int before=0) const; //number of 1's
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unsigned int population(const unsigned int before=0) const; //number of 1's (Hamming weight)
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unsigned int nlz() const; //number of leading zeroes
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unsigned int degree() const {if(iszero()) return 0; else return size()-nlz()-1;}; //interprested as a polynomial over GF(2)
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void truncate(int t=0) {int s=degree()+1; if(t>s) s=t; resize(s,true);};
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@ -117,6 +126,8 @@ public:
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void write(int fd, bool dimensions=1, bool transp=0);
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};
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extern bitvector find_irreducible(int deg, int pop= -1, int nth=1); //degree and requested Hamming weight or -1 for random trial
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//expand to separate bytes or ints
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template <typename T>
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void bitvector_expand(const bitvector &v, NRVec<T> &r)
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13
laerror.cc
13
laerror.cc
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@ -205,4 +205,17 @@ extern "C" int cblas_errprn(int ierr, int info, char *form, ...) {
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}
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#endif
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int endianity()
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{
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static union {int i; char z[sizeof(int)];} u;
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static int jj= -1;
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if(jj<0) /* first call */
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{
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u.i=1;
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jj=0; while(!u.z[jj]) jj++;
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}
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return jj;
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}
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}//namespace
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@ -53,6 +53,8 @@ s << x.msg;
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return s;
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}
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extern int endianity();
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}//namespace
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#endif
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47
t.cc
47
t.cc
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@ -2946,7 +2946,7 @@ cin >>n;
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cout <<factorization(n)<<" phi = "<<eulerphi(n)<<endl;
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}
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if(1)
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if(0)
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{
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bitvector ir; cin >>ir;
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if(!ir.is_irreducible()) laerror("input must be an irreducible polynomial");
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@ -2961,8 +2961,49 @@ bitvector cc=a.field_composition(ai,ir);
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cout <<c<<endl;
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cout <<c%ir<<endl;
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cout <<cc<<endl;
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}
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if(1)
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{
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int seed;
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int f=open("/dev/random",O_RDONLY);
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if(sizeof(int)!=read(f,&seed,sizeof(int))) laerror("cannot read /dev/random");
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close(f);
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srand(seed);
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int d;
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cin >>d;
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bitvector ir=find_irreducible(d,3);
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if(ir.is_zero()) ir=find_irreducible(d,5);
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if(ir.is_zero()) ir=find_irreducible(d,7);
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if(ir.is_zero()) {cout<<"cannot find IR polynomial\n"; exit(1);}
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cout <<"IR = "<<ir<<endl;
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if(!ir.is_irreducible()) laerror("error in IR finder");
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else cout <<"IS irreducible\n";
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bitvector a(d);
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do { a.randomize(); }while(a.is_zero());
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cout <<"A = "<<a<<endl;
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bitvector aa=a;
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cout <<"A+1 = "<<++aa<<endl;
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cout <<"A+1-1 = "<<--aa<<endl;
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if(a!=aa) laerror("error in inc/dec");
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bitvector g=ir.gcd(a);
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cout<<"GCD A,IR = "<<g<<endl;
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if(!g.is_one() && !a.is_zero()) laerror("ERROR IN is_irreducible\n");
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bitvector ai = a.field_inv(ir);
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cout <<"I = "<<ai<<endl;
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bitvector check = a.field_mult(ai,ir);
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cout<<"check " <<check<<endl;
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if(!check.is_one()) laerror("error in GF(2^n) inversion");
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bitvector s=a.field_sqrt(ir);
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cout <<"test a "<<a<<endl;
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cout <<"tests2 "<<s.field_mult(s,ir)<<endl;
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cout <<"test s "<<s<<endl;
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bitvector dif=a - s.field_mult(s,ir);
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if(!dif.is_zero()) laerror("error in gf 2^n sqrt");
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}
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}
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}
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