Regina Calculation Engine
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Represents a finitely generated abelian group. More...
#include <algebra/nabeliangroup.h>
Public Member Functions | |
NAbelianGroup () | |
Creates a new trivial group. | |
NAbelianGroup (const NAbelianGroup &cloneMe) | |
Creates a clone of the given group. | |
NAbelianGroup (const NMatrixInt &M, const NMatrixInt &N) | |
Creates an abelian group as the homology of a chain complex. | |
NAbelianGroup (const NMatrixInt &M, const NMatrixInt &N, const NLargeInteger &p) | |
Creates an abelian group as the homology of a chain complex, using mod-p coefficients. | |
virtual | ~NAbelianGroup () |
Destroys the group. | |
void | addRank (int extraRank=1) |
Increments the rank of the group by the given integer. | |
void | addTorsionElement (const NLargeInteger °ree, unsigned mult=1) |
Adds the given torsion element to the group. | |
void | addTorsionElement (unsigned long degree, unsigned mult=1) |
Adds the given torsion element to the group. | |
void | addTorsionElements (const std::multiset< NLargeInteger > &torsion) |
Adds the given set of torsion elements to this group. | |
void | addGroup (const NMatrixInt &presentation) |
Adds the abelian group defined by the given presentation to this group. | |
void | addGroup (const NAbelianGroup &group) |
Adds the given abelian group to this group. | |
unsigned | getRank () const |
Returns the rank of the group. | |
unsigned | getTorsionRank (const NLargeInteger °ree) const |
Returns the rank in the group of the torsion term of given degree. | |
unsigned | getTorsionRank (unsigned long degree) const |
Returns the rank in the group of the torsion term of given degree. | |
unsigned long | getNumberOfInvariantFactors () const |
Returns the number of invariant factors that describe the torsion elements of this group. | |
const NLargeInteger & | getInvariantFactor (unsigned long index) const |
Returns the given invariant factor describing the torsion elements of this group. | |
bool | isTrivial () const |
Determines whether this is the trivial (zero) group. | |
bool | operator== (const NAbelianGroup &other) const |
Determines whether this and the given abelian group are isomorphic. | |
void | writeXMLData (std::ostream &out) const |
Writes a chunk of XML containing this abelian group. | |
void | writeToFile (NFile &out) const |
Writes this abelian group to the given old-style binary file. | |
virtual void | writeTextShort (std::ostream &out) const |
The text representation will be of the form 3 Z + 4 Z_2 + Z_120 . | |
Static Public Member Functions | |
static NAbelianGroup * | readFromFile (NFile &in) |
Reads an abelian group from the given old-style binary file. | |
Protected Member Functions | |
void | replaceTorsion (const NMatrixInt &matrix) |
Replaces the torsion elements of this group with those in the abelian group represented by the given Smith normal form presentation matrix. | |
Protected Attributes | |
unsigned | rank |
The rank of the group (the number of Z components). | |
std::multiset< NLargeInteger > | invariantFactors |
The invariant factors d0,...,dn as described in the NAbelianGroup notes. |
Represents a finitely generated abelian group.
The torsion elements of the group are stored in terms of their invariant factors. For instance, Z_2+Z_3 will appear as Z_6, and Z_2+Z_2+Z_3 will appear as Z_2+Z_6.
In general the factors will appear as Z_d0+...+Z_dn, where the invariant factors di are all greater than 1 and satisfy d0|d1|...|dn. Note that this representation is unique.
regina::NAbelianGroup::NAbelianGroup | ( | ) | [inline] |
Creates a new trivial group.
regina::NAbelianGroup::NAbelianGroup | ( | const NAbelianGroup & | cloneMe | ) | [inline] |
Creates a clone of the given group.
cloneMe | the group to clone. |
regina::NAbelianGroup::NAbelianGroup | ( | const NMatrixInt & | M, |
const NMatrixInt & | N | ||
) |
Creates an abelian group as the homology of a chain complex.
M | the `right' matrix in the chain complex; that is, the matrix that one takes the kernel of when computing homology. |
N | the `left' matrix in the chain complex; that is, the matrix that one takes the image of when computing homology. |
regina::NAbelianGroup::NAbelianGroup | ( | const NMatrixInt & | M, |
const NMatrixInt & | N, | ||
const NLargeInteger & | p | ||
) |
Creates an abelian group as the homology of a chain complex, using mod-p coefficients.
M | the `right' matrix in the chain complex; that is, the matrix that one takes the kernel of when computing homology. |
N | the `left' matrix in the chain complex; that is, the matrix that one takes the image of when computing homology. |
p | the modulus, which may be any NLargeInteger. Zero is interpreted as a request for integer coefficents, which will give the same result as the NAbelianGroup(const NMatrixInt&, const NMatrixInt&) constructor. |
regina::NAbelianGroup::~NAbelianGroup | ( | ) | [inline, virtual] |
Destroys the group.
void regina::NAbelianGroup::addGroup | ( | const NMatrixInt & | presentation | ) |
Adds the abelian group defined by the given presentation to this group.
Note that this routine might be slow since calculating the new invariant factors is not trivial.
presentation | a presentation matrix for the group to be added to this group, where each column represents a generator and each row a relation. |
void regina::NAbelianGroup::addGroup | ( | const NAbelianGroup & | group | ) |
Adds the given abelian group to this group.
Note that this routine might be slow since calculating the new invariant factors is not trivial.
group | the group to add to this one. |
void regina::NAbelianGroup::addRank | ( | int | extraRank = 1 | ) | [inline] |
Increments the rank of the group by the given integer.
This integer may be positive, negative or zero.
extraRank | the extra rank to add; this defaults to 1. |
void regina::NAbelianGroup::addTorsionElement | ( | const NLargeInteger & | degree, |
unsigned | mult = 1 |
||
) |
Adds the given torsion element to the group.
Note that this routine might be slow since calculating the new invariant factors is not trivial. If many different torsion elements are to be added, consider using addTorsionElements() instead so the invariant factors need only be calculated once.
In this routine we add a specified number of copies of Z_d, where d is some given degree.
degree | d, where we are adding copies of Z_d to the torsion. |
mult | the multiplicity m, where we are adding precisely m copies of Z_d; this defaults to 1. |
void regina::NAbelianGroup::addTorsionElement | ( | unsigned long | degree, |
unsigned | mult = 1 |
||
) | [inline] |
Adds the given torsion element to the group.
Note that this routine might be slow since calculating the new invariant factors is not trivial. If many different torsion elements are to be added, consider using addTorsionElements() instead so the invariant factors need only be calculated once.
In this routine we add a specified number of copies of Z_d, where d is some given degree.
degree | d, where we are adding copies of Z_d to the torsion. |
mult | the multiplicity m, where we are adding precisely m copies of Z_d; this defaults to 1. |
void regina::NAbelianGroup::addTorsionElements | ( | const std::multiset< NLargeInteger > & | torsion | ) |
Adds the given set of torsion elements to this group.
Note that this routine might be slow since calculating the new invariant factors is not trivial.
The torsion elements to add are described by a list of integers k1,...,km, where we are adding Z_k1,...,Z_km. Unlike invariant factors, the ki are not required to divide each other.
torsion | a list containing the torsion elements to add, as described above. |
const NLargeInteger& regina::NAbelianGroup::getInvariantFactor | ( | unsigned long | index | ) | const |
Returns the given invariant factor describing the torsion elements of this group.
See the NAbelianGroup class notes for further details.
If the invariant factors are d0|d1|...|dn, this routine will return di where i is the value of parameter index.
index | the index of the invariant factor to return; this must be between 0 and getNumberOfInvariantFactors()-1 inclusive. |
unsigned long regina::NAbelianGroup::getNumberOfInvariantFactors | ( | ) | const [inline] |
Returns the number of invariant factors that describe the torsion elements of this group.
See the NAbelianGroup class notes for further details.
unsigned regina::NAbelianGroup::getRank | ( | ) | const [inline] |
Returns the rank of the group.
This is the number of included copies of Z.
unsigned regina::NAbelianGroup::getTorsionRank | ( | const NLargeInteger & | degree | ) | const |
Returns the rank in the group of the torsion term of given degree.
If the given degree is d, this routine will return the largest m for which mZ_d is a subgroup of this group.
For instance, if this group is Z_6+Z_12, the torsion term of degree 2 has rank 2 (one occurrence in Z_6 and one in Z_12), and the torsion term of degree 4 has rank 1 (one occurrence in Z_12).
degree | the degree of the torsion term to query. |
unsigned regina::NAbelianGroup::getTorsionRank | ( | unsigned long | degree | ) | const [inline] |
Returns the rank in the group of the torsion term of given degree.
If the given degree is d, this routine will return the largest m for which mZ_d is a subgroup of this group.
For instance, if this group is Z_6+Z_12, the torsion term of degree 2 has rank 2 (one occurrence in Z_6 and one in Z_12), and the torsion term of degree 4 has rank 1 (one occurrence in Z_12).
degree | the degree of the torsion term to query. |
bool regina::NAbelianGroup::isTrivial | ( | ) | const [inline] |
Determines whether this is the trivial (zero) group.
true
if and only if this is the trivial group. bool regina::NAbelianGroup::operator== | ( | const NAbelianGroup & | other | ) | const [inline] |
Determines whether this and the given abelian group are isomorphic.
other | the group with which this should be compared. |
true
if and only if the two groups are isomorphic. static NAbelianGroup* regina::NAbelianGroup::readFromFile | ( | NFile & | in | ) | [static] |
Reads an abelian group from the given old-style binary file.
The group will be newly allocated, and responsibility for its destruction lies with the caller of this routine.
in | the file from which to read. |
void regina::NAbelianGroup::replaceTorsion | ( | const NMatrixInt & | matrix | ) | [protected] |
Replaces the torsion elements of this group with those in the abelian group represented by the given Smith normal form presentation matrix.
Any zero columns in the matrix will also be added to the rank as additional copies of Z. Note that preexisting torsion elements will be deleted, but preexisting rank will not.
matrix | a matrix containing the Smith normal form presentation matrix for the new torsion elements, where each column represents a generator and each row a relation. |
virtual void regina::NAbelianGroup::writeTextShort | ( | std::ostream & | out | ) | const [virtual] |
The text representation will be of the form 3 Z + 4 Z_2 + Z_120
.
The torsion elements will be written in terms of the invariant factors of the group, as described in the NAbelianGroup notes.
Implements regina::ShareableObject.
void regina::NAbelianGroup::writeToFile | ( | NFile & | out | ) | const |
Writes this abelian group to the given old-style binary file.
out | the file to which to write. |
void regina::NAbelianGroup::writeXMLData | ( | std::ostream & | out | ) | const |
Writes a chunk of XML containing this abelian group.
out | the output stream to which the XML should be written. |
std::multiset<NLargeInteger> regina::NAbelianGroup::invariantFactors [protected] |
The invariant factors d0,...,dn as described in the NAbelianGroup notes.
unsigned regina::NAbelianGroup::rank [protected] |
The rank of the group (the number of Z components).