jiri/LA_library
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

bitvector: polynomial ring over GF(2) operations

Browse Source
This commit is contained in:
Jiri Pittner
2023-12-28 17:06:07 +01:00
parent c428d4650c
commit 1a38fe48ba
4 changed files with 229 additions and 18 deletions
Download Patch File Download Diff File Expand all files Collapse all files

23
bitvector.h
View File

@@ -25,7 +25,7 @@
namespace LA {
//compressed storage of large bit vectors
//let's now use 64-bit blocks exclusively
//let's now use 64-bit blocks exclusively for simplicity
typedef uint64_t bitvector_block;
@@ -48,10 +48,10 @@ public:
//operator= seems to be correctly synthetized by the compiler
//override dereferencing to address single bits, is however possible
//only in the const context (otherwise we would have to define a type which, when assigned to, changes a single bit - possible but probably inefficient)
void resize(const unsigned int n, bool preserve=false) {NRVec<bitvector_block>::resize((n+blockbits-1)/blockbits,preserve); modulo=n%blockbits;};
void resize(const unsigned int n, bool preserve=false); //preserve data or clear
unsigned int size() const {return (nn*blockbits)-blockbits+(modulo?modulo:blockbits);};
//arguments must be unsigned to keep the resulting assembly code simple and efficient
const bool operator[](const unsigned int i) const {return (v[i/blockbits] >>(i%blockbits))&1UL;};
const bool operator[](const unsigned int i) const {return (v[i/blockbits] >>(i%blockbits))&1ULL;};
const bool get(const unsigned int i) const {return (*this)[i];};
bitvector_block getblock(const unsigned int i) const {return v[i];}; //integer interpretation
void setblock(const unsigned int i, const bitvector_block b) {v[i]=b;};
@@ -62,6 +62,8 @@ public:
void clear() {copyonwrite(true); memset(v,0,nn*sizeof(bitvector_block));};
void fill() {memset(v,0xff,nn*sizeof(bitvector_block));};
bool iszero() const {for(int i=0; i<nn; ++i) if(v[i]) return false; return true;};
bool is_zero() const {return iszero();};
bool is_one() const {if(v[0]!=1) return false; for(int i=1; i<nn; ++i) if(v[i]) return false; return true;};
void randomize();
bool operator!=(const bitvector &rhs) const;
bool operator==(const bitvector &rhs) const {return !(*this != rhs);};
@@ -80,15 +82,24 @@ public:
bitvector operator^(const bitvector &rhs) const {return bitvector(*this) ^= rhs;};
bitvector operator+(const bitvector &rhs) const {return *this ^ rhs;}; //addition modulo 2
bitvector operator-(const bitvector &rhs) const {return *this ^ rhs;}; //subtraction modulo 2
unsigned int operator%(const bitvector &y) const; //number of differing bits
bitvector operator*(const bitvector &rhs) const; //multiplication of polynomials over GF(2) NOTE: naive algorithm, does not employ CLMUL nor fft-like approach, only for short vectors!!!
bitvector division(const bitvector &rhs, bitvector &remainder) const;
bitvector operator/(const bitvector &rhs) const {bitvector rem(rhs.size()); return division(rhs,rem);};
bitvector operator%(const bitvector &rhs) const {bitvector rem(rhs.size()); division(rhs,rem); return rem;};
bitvector gcd(const bitvector &rhs) const;
bitvector lcm(const bitvector &rhs) const {return (*this)*rhs/this->gcd(rhs);};
unsigned int bitdiff(const bitvector &y) const; //number of differing bits
unsigned int population(const unsigned int before=0) const; //number of 1's
unsigned int nlz() const; //number of leading zeroes
unsigned int degree() const {if(iszero()) return 0; else return size()-nlz()-1;}; //interprested as a polynomial over GF(2)
unsigned int ntz() const; //number of trailing zeroes
//extended, truncated const i.e. not on *this but return new entity, take care of modulo's bits
//logical shifts
bitvector& operator>>=(unsigned int i);
bitvector& leftshift(unsigned int i, bool autoresize=false);
bitvector& operator<<=(unsigned int i) {return leftshift(i,true);};
bitvector operator>>(unsigned int i) {bitvector r(*this); return r>>=i;};
bitvector operator<<(unsigned int i) {bitvector r(*this); return r<<=i;};
bitvector operator>>(unsigned int i) const {bitvector r(*this); return r>>=i;};
bitvector operator<<(unsigned int i) const {bitvector r(*this); return r<<=i;};
//logical rotations not implemented yet
//unformatted file IO
void read(int fd, bool dimensions=1, bool transp=0);