  
  [1X4 [33X[0;0YGaussian Algorithms[133X[101X
  
  
  [1X4.1 [33X[0;0YA list of the available algorithms[133X[101X
  
  [33X[0;0YAs  decribed earlier, the main functions of [5XGauss[105X are [2XEchelonMat[102X ([14X4.2-1[114X) and
  [2XEchelonMatTransformation[102X       ([14X4.2-2[114X),      [2XReduceMat[102X      ([14X4.2-3[114X)      and
  [2XReduceMatTransformation[102X  ([14X4.2-4[114X),  [2XKernelMat[102X  ([14X4.2-5[114X) and, additionally [2XRank[102X
  ([14X4.2-6[114X). These are all documented in the next section, but of course rely on
  specific  algorithms depending on the base ring of the matrix. These are not
  fully  documented but it should be very easy to find out how they work based
  on the documentation of the main functions.[133X
  
        EchelonMat                                                                        
                                   Field:            [10XEchelonMatDestructive[110X                
                                   Ring:             [10XHermiteMatDestructive[110X                
        EchelonMatTransformation                                                          
                                   Field:            [10XEchelonMatTransformationDestructive[110X  
                                   Ring:             [10XHermiteMatTransformationDestructive[110X  
        ReduceMat                                                                         
                                   Field:            [10XReduceMatWithEchelonMat[110X              
                                   Ring:             [10XReduceMatWithHermiteMat[110X              
        ReduceMatTransformation                                                           
                                   Field:            [10XReduceMatWithEchelonMatTransformation[110X
                                   Ring:             [10XReduceMatWithHermiteMatTransformation[110X
        KernelMat                                                                         
                                   Field:            [10XKernelEchelonMatDestructive[110X          
                                   Ring:             [10XKernelHermiteMatDestructive[110X          
        Rank                                                                              
                                   Field (dense):    [10XRank[110X ([5XGAP[105X method)                    
                                   Field (sparse):   [10XRankDestructive[110X                      
                                   GF(2) (sparse):   [10XRankOfIndicesListList[110X                
                                   Ring:             n.a.                                 
  
  
  [1X4.2 [33X[0;0YMethods and Functions for [5XGauss[105X[101X[1Xian algorithms[133X[101X
  
  [1X4.2-1 EchelonMat[101X
  
  [29X[2XEchelonMat[102X( [3Xmat[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ya  record  that  contains information about an echelonized form of
            the matrix [3Xmat[103X.[133X
  
            [33X[0;10YThe components of this record are[133X
  
            [33X[0;10Y`vectors'[133X
  
            [33X[0;10Ythe  reduced  row echelon / hermite form of the matrix [3Xmat[103X without
            zero rows.[133X
  
            [33X[0;10Y`heads'[133X
  
            [33X[0;10Ylist  that contains at position <i>, if nonzero, the number of the
            row for that the pivot element is in column <i>.[133X
  
  [33X[0;0Ycomputes  the  reduced row echelon form RREF of a dense or sparse matrix [3Xmat[103X
  over a field, or the hermite form of a sparse matrix [3Xmat[103X over [22Xℤ / < p^n >[122X.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27XM := [[0,0,0,1,0],[0,1,1,1,1],[1,1,1,1,0]] * One( GF(2) );;[127X[104X
    [4X[25Xgap>[125X [27XDisplay(M);[127X[104X
    [4X[28X . . . 1 .[128X[104X
    [4X[28X . 1 1 1 1[128X[104X
    [4X[28X 1 1 1 1 .[128X[104X
    [4X[25Xgap>[125X [27XEchelonMat(M);[127X[104X
    [4X[28Xrec( heads := [ 1, 2, 0, 3, 0 ],[128X[104X
    [4X[28X  vectors := [ <an immutable GF2 vector of length 5>,[128X[104X
    [4X[28X      <an immutable GF2 vector of length 5>,[128X[104X
    [4X[28X      <an immutable GF2 vector of length 5> ] )[128X[104X
    [4X[25Xgap>[125X [27XDisplay( last.vectors );[127X[104X
    [4X[28X 1 . . . 1[128X[104X
    [4X[28X . 1 1 . 1[128X[104X
    [4X[28X . . . 1 .[128X[104X
    [4X[25Xgap>[125X [27XSM := SparseMatrix( M );[127X[104X
    [4X[28X<a 3 x 5 sparse matrix over GF(2)>[128X[104X
    [4X[25Xgap>[125X [27XEchelonMat( SM );[127X[104X
    [4X[28Xrec( heads := [ 1, 2, 0, 3, 0 ], vectors := <a 3 x 5 sparse matrix over GF([128X[104X
    [4X[28X    2)> )[128X[104X
    [4X[25Xgap>[125X [27XDisplay(last.vectors);[127X[104X
    [4X[28X 1 . . . 1[128X[104X
    [4X[28X . 1 1 . 1[128X[104X
    [4X[28X . . . 1 .[128X[104X
    [4X[25Xgap>[125X [27XSM := SparseMatrix( [[7,4,5],[0,0,6],[0,4,4]] * One( Integers mod 8 ) );[127X[104X
    [4X[28X<a 3 x 3 sparse matrix over (Integers mod 8)>[128X[104X
    [4X[25Xgap>[125X [27XDisplay( SM );[127X[104X
    [4X[28X 7 4 5[128X[104X
    [4X[28X . . 6[128X[104X
    [4X[28X . 4 4[128X[104X
    [4X[25Xgap>[125X [27XEchelonMat( SM );[127X[104X
    [4X[28Xrec( heads := [ 1, 2, 3 ],[128X[104X
    [4X[28X  vectors := <a 3 x 3 sparse matrix over (Integers mod 8)> )[128X[104X
    [4X[25Xgap>[125X [27XDisplay( last.vectors );[127X[104X
    [4X[28X 1 . 1[128X[104X
    [4X[28X . 4 .[128X[104X
    [4X[28X . . 2      [128X[104X
  [4X[32X[104X
  
  [1X4.2-2 EchelonMatTransformation[101X
  
  [29X[2XEchelonMatTransformation[102X( [3Xmat[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ya  record  that  contains information about an echelonized form of
            the matrix [3Xmat[103X.[133X
  
            [33X[0;10YThe components of this record are[133X
  
            [33X[0;10Y`vectors'[133X
  
            [33X[0;10Ythe  reduced  row echelon / hermite form of the matrix [3Xmat[103X without
            zero rows.[133X
  
            [33X[0;10Y`heads'[133X
  
            [33X[0;10Ylist  that contains at position <i>, if nonzero, the number of the
            row for that the pivot element is in column <i>.[133X
  
            [33X[0;10Y`coeffs'[133X
  
            [33X[0;10Ythe transformation matrix needed to obtain the RREF from [3Xmat[103X.[133X
  
            [33X[0;10Y`relations'[133X
  
            [33X[0;10Ythe  kernel of the matrix [3Xmat[103X if RingOfDefinition([3Xmat[103X) is a field.
            Otherwise  these  are only the obvious row relations of [3Xmat[103X, there
            might be more kernel vectors - --> [2XKernelMat[102X ([14X4.2-5[114X).[133X
  
  [33X[0;0Ycomputes  the  reduced row echelon form RREF of a dense or sparse matrix [3Xmat[103X
  over  a  field, or the hermite form of a sparse matrix [3Xmat[103X over [22Xℤ / < p^n >[122X.
  In  either  case, the transformation matrix [22XT[122X is calculated as the row union
  of `coeffs' and `relations'.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27XM := [[1,0,1],[1,1,0],[1,0,1],[1,1,0],[1,1,1]] * One( GF(2) );;[127X[104X
    [4X[25Xgap>[125X [27XEchelonMatTransformation( M );[127X[104X
    [4X[28Xrec( [128X[104X
    [4X[28X  coeffs := [ <an immutable GF2 vector of length 5>,[128X[104X
    [4X[28X      <an immutable GF2 vector of length 5>, [128X[104X
    [4X[28X      <an immutable GF2 vector of length 5> ], heads := [ 1, 2, 3 ], [128X[104X
    [4X[28X  relations := [128X[104X
    [4X[28X    [ <an immutable GF2 vector of length 5>,[128X[104X
    [4X[28X      <an immutable GF2 vector of length 5> ], [128X[104X
    [4X[28X  vectors := [ <an immutable GF2 vector of length 3>,[128X[104X
    [4X[28X      <an immutable GF2 vector of length 3>,[128X[104X
    [4X[28X      <an immutable GF2 vector of length 3> ] )[128X[104X
    [4X[25Xgap>[125X [27XDisplay(last.vectors);[127X[104X
    [4X[28X 1 . .[128X[104X
    [4X[28X . 1 .[128X[104X
    [4X[28X . . 1[128X[104X
    [4X[25Xgap>[125X [27XDisplay(last.coeffs);[127X[104X
    [4X[28X 1 1 . . 1[128X[104X
    [4X[28X 1 . . . 1[128X[104X
    [4X[28X . 1 . . 1[128X[104X
    [4X[25Xgap>[125X [27XDisplay(last.relations);[127X[104X
    [4X[28X 1 . 1 . .[128X[104X
    [4X[28X . 1 . 1 .[128X[104X
    [4X[25Xgap>[125X [27XDisplay( Concatenation( last.coeffs, last.relations ) * M );[127X[104X
    [4X[28X 1 . .[128X[104X
    [4X[28X . 1 .[128X[104X
    [4X[28X . . 1[128X[104X
    [4X[28X . . .[128X[104X
    [4X[28X . . .[128X[104X
    [4X[25Xgap>[125X [27XSM := SparseMatrix( M );[127X[104X
    [4X[28X<a 5 x 3 sparse matrix over GF(2)>[128X[104X
    [4X[25Xgap>[125X [27XEchelonMatTransformation( SM );[127X[104X
    [4X[28Xrec( coeffs := <a 3 x 5 sparse matrix over GF(2)>, [128X[104X
    [4X[28X  heads := [ 1, 2, 3 ], [128X[104X
    [4X[28X  relations := <a 2 x 5 sparse matrix over GF(2)>, [128X[104X
    [4X[28X  vectors := <a 3 x 3 sparse matrix over GF(2)> )[128X[104X
    [4X[25Xgap>[125X [27XDisplay(last.vectors);[127X[104X
    [4X[28X 1 . .[128X[104X
    [4X[28X . 1 .[128X[104X
    [4X[28X . . 1[128X[104X
    [4X[25Xgap>[125X [27XDisplay(last.coeffs);[127X[104X
    [4X[28X 1 1 . . 1[128X[104X
    [4X[28X 1 . . . 1[128X[104X
    [4X[28X . 1 . . 1[128X[104X
    [4X[25Xgap>[125X [27XDisplay(last.relations);[127X[104X
    [4X[28X 1 . 1 . .[128X[104X
    [4X[28X . 1 . 1 .[128X[104X
    [4X[25Xgap>[125X [27XDisplay( UnionOfRows( last.coeffs, last.relations ) * SM );[127X[104X
    [4X[28X 1 . .[128X[104X
    [4X[28X . 1 .[128X[104X
    [4X[28X . . 1[128X[104X
    [4X[28X . . .[128X[104X
    [4X[28X . . .[128X[104X
  [4X[32X[104X
  
  [1X4.2-3 ReduceMat[101X
  
  [29X[2XReduceMat[102X( [3XA[103X, [3XB[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ya  record  with  a  single  component  `reduced_matrix' := M. M is
            created  by  reducing [3XA[103X with [3XB[103X, where [3XB[103X must be in Echelon/Hermite
            form. M will have the same dimensions as [3XA[103X.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27XM := [[0,0,0,1,0],[0,1,1,1,1],[1,1,1,1,0]] * One( GF(2) );;[127X[104X
    [4X[25Xgap>[125X [27XDisplay(M);[127X[104X
    [4X[28X . . . 1 .[128X[104X
    [4X[28X . 1 1 1 1[128X[104X
    [4X[28X 1 1 1 1 .[128X[104X
    [4X[25Xgap>[125X [27XN := [[1,1,0,0,0],[0,0,1,0,1]] * One( GF(2) );;[127X[104X
    [4X[25Xgap>[125X [27XDisplay(N);[127X[104X
    [4X[28X 1 1 . . .[128X[104X
    [4X[28X . . 1 . 1[128X[104X
    [4X[25Xgap>[125X [27XReduceMat(M,N);[127X[104X
    [4X[28Xrec([128X[104X
    [4X[28X  reduced_matrix := [ <a GF2 vector of length 5>, <a GF2 vector of length 5>,[128X[104X
    [4X[28X      <a GF2 vector of length 5> ] )[128X[104X
    [4X[25Xgap>[125X [27XDisplay(last.reduced_matrix);[127X[104X
    [4X[28X . . . 1 .[128X[104X
    [4X[28X . 1 . 1 .[128X[104X
    [4X[28X . . . 1 1[128X[104X
    [4X[25Xgap>[125X [27XSM := SparseMatrix(M); SN := SparseMatrix(N);[127X[104X
    [4X[28X<a 3 x 5 sparse matrix over GF(2)>[128X[104X
    [4X[28X<a 2 x 5 sparse matrix over GF(2)>[128X[104X
    [4X[25Xgap>[125X [27XReduceMat(SM,SN);[127X[104X
    [4X[28Xrec( reduced_matrix := <a 3 x 5 sparse matrix over GF(2)> )[128X[104X
    [4X[25Xgap>[125X [27XDisplay(last.reduced_matrix);[127X[104X
    [4X[28X . . . 1 .[128X[104X
    [4X[28X . 1 . 1 .[128X[104X
    [4X[28X . . . 1 1[128X[104X
  [4X[32X[104X
  
  [1X4.2-4 ReduceMatTransformation[101X
  
  [29X[2XReduceMatTransformation[102X( [3XA[103X, [3XB[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ya  record  with a component `reduced_matrix' := M. M is created by
            reducing [3XA[103X with [3XB[103X, where [3XB[103X must be in Echelon/Hermite form. M will
            have  the  same  dimensions  as  [3XA[103X. In addition to the (identical)
            output  as  ReduceMat  this  record  also  includes  the component
            `transformation', which stores the row operations that were needed
            to  reduce  [3XA[103X  with  [3XB[103X.  This differs from "normal" transformation
            matrices  because  only  rows of [3XB[103X had to be moved. Therefore, the
            transformation matrix solves M = A + T * B.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27XM := [[0,0,0,1,0],[0,1,1,1,1],[1,1,1,1,0]] * One( GF(2) );;[127X[104X
    [4X[25Xgap>[125X [27XDisplay(M);[127X[104X
    [4X[28X . . . 1 .[128X[104X
    [4X[28X . 1 1 1 1[128X[104X
    [4X[28X 1 1 1 1 .[128X[104X
    [4X[25Xgap>[125X [27XN := [[1,1,0,0,0],[0,0,1,0,1]] * One( GF(2) );;[127X[104X
    [4X[25Xgap>[125X [27XDisplay(N);[127X[104X
    [4X[28X 1 1 . . .[128X[104X
    [4X[28X . . 1 . 1[128X[104X
    [4X[25Xgap>[125X [27XReduceMatTransformation(M,N);[127X[104X
    [4X[28Xrec( [128X[104X
    [4X[28X  reduced_matrix := [128X[104X
    [4X[28X    [ <a GF2 vector of length 5>, <a GF2 vector of length 5>, [128X[104X
    [4X[28X      <a GF2 vector of length 5> ], [128X[104X
    [4X[28X  transformation := <a 3x2 matrix over GF2> )[128X[104X
    [4X[25Xgap>[125X [27XDisplay(last.reduced_matrix);[127X[104X
    [4X[28X . . . 1 .[128X[104X
    [4X[28X . 1 . 1 .[128X[104X
    [4X[28X . . . 1 1[128X[104X
    [4X[25Xgap>[125X [27XDisplay(last.transformation);[127X[104X
    [4X[28X . .[128X[104X
    [4X[28X . 1[128X[104X
    [4X[28X 1 1[128X[104X
    [4X[25Xgap>[125X [27XDisplay( M + last.transformation * N );[127X[104X
    [4X[28X . . . 1 .[128X[104X
    [4X[28X . 1 . 1 .[128X[104X
    [4X[28X . . . 1 1 [128X[104X
    [4X[25Xgap>[125X [27XSM := SparseMatrix(M); SN := SparseMatrix(N);[127X[104X
    [4X[28X<a 3 x 5 sparse matrix over GF(2)>[128X[104X
    [4X[28X<a 2 x 5 sparse matrix over GF(2)>[128X[104X
    [4X[25Xgap>[125X [27XReduceMatTransformation(SM,SN);[127X[104X
    [4X[28Xrec( reduced_matrix := <a 3 x 5 sparse matrix over GF(2)>,[128X[104X
    [4X[28X  transformation := <a 3 x 2 sparse matrix over GF(2)> )[128X[104X
    [4X[25Xgap>[125X [27XDisplay(last.reduced_matrix);[127X[104X
    [4X[28X . . . 1 .[128X[104X
    [4X[28X . 1 . 1 .[128X[104X
    [4X[28X . . . 1 1[128X[104X
    [4X[25Xgap>[125X [27XDisplay(last.transformation);[127X[104X
    [4X[28X . .[128X[104X
    [4X[28X . 1[128X[104X
    [4X[28X 1 1[128X[104X
    [4X[25Xgap>[125X [27XDisplay( SM + last.transformation * SN );[127X[104X
    [4X[28X . . . 1 .[128X[104X
    [4X[28X . 1 . 1 .[128X[104X
    [4X[28X . . . 1 1[128X[104X
  [4X[32X[104X
  
  [1X4.2-5 KernelMat[101X
  
  [29X[2XKernelMat[102X( [3XM[103X ) [32X function
  [6XReturns:[106X  [33X[0;10Ya record with a single component `relations'.[133X
  
  [33X[0;0YIf   [3XM[103X   is   a   matrix   over   a   field  this  is  the  same  output  as
  [2XEchelonMatTransformation[102X  ([14X4.2-2[114X) provides in the `relations' component, but
  with  less  memory  and CPU usage. If the base ring of [3XM[103X is a non-field, the
  Kernel might have additional generators, which are added to the output.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27XM := [[2,1],[0,2]];[127X[104X
    [4X[28X[ [ 2, 1 ], [ 0, 2 ] ][128X[104X
    [4X[25Xgap>[125X [27XSM := SparseMatrix( M * One( GF(3) ) );[127X[104X
    [4X[28X<a 2 x 2 sparse matrix over GF(3)>[128X[104X
    [4X[25Xgap>[125X [27XKernelMat(SM);[127X[104X
    [4X[28Xrec( relations := <a 0 x 2 sparse matrix over GF(3)> )[128X[104X
    [4X[25Xgap>[125X [27XSN := SparseMatrix( M * One( Integers mod 4 ) );[127X[104X
    [4X[28X<a 2 x 2 sparse matrix over (Integers mod 4)>[128X[104X
    [4X[25Xgap>[125X [27XKernelMat(SN);[127X[104X
    [4X[28Xrec( relations := <a 1 x 2 sparse matrix over (Integers mod 4)> )[128X[104X
    [4X[25Xgap>[125X [27XDisplay(last.relations);[127X[104X
    [4X[28X 2 1[128X[104X
  [4X[32X[104X
  
  [1X4.2-6 Rank[101X
  
  [29X[2XRank[102X( [3Xsm[103X[, [3Xboundary[103X] ) [32X method
  [6XReturns:[106X  [33X[0;10Ythe rank of the sparse matrix [3Xsm[103X. Only works for fields.[133X
  
  [33X[0;0YComputes  the  rank of a sparse matrix. If the optional argument [3Xboundary[103X is
  provided,  some  algorithms  take  into  account  the  fact that Rank([3Xsm[103X) <=
  [3Xboundary[103X, thus possibly terminating earlier.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27XM := SparseDiagMat( ListWithIdenticalEntries( 10,[127X[104X
    [4X[25X>[125X [27X        SparseMatrix( [[1,1],[1,1]] * One( GF(5) ) ) ) );[127X[104X
    [4X[28X<a 20 x 20 sparse matrix over GF(5)>[128X[104X
    [4X[25Xgap>[125X [27XDisplay(M);[127X[104X
    [4X[28X 1 1 . . . . . . . . . . . . . . . . . .[128X[104X
    [4X[28X 1 1 . . . . . . . . . . . . . . . . . .[128X[104X
    [4X[28X . . 1 1 . . . . . . . . . . . . . . . .[128X[104X
    [4X[28X . . 1 1 . . . . . . . . . . . . . . . .[128X[104X
    [4X[28X . . . . 1 1 . . . . . . . . . . . . . .[128X[104X
    [4X[28X . . . . 1 1 . . . . . . . . . . . . . .[128X[104X
    [4X[28X . . . . . . 1 1 . . . . . . . . . . . .[128X[104X
    [4X[28X . . . . . . 1 1 . . . . . . . . . . . .[128X[104X
    [4X[28X . . . . . . . . 1 1 . . . . . . . . . .[128X[104X
    [4X[28X . . . . . . . . 1 1 . . . . . . . . . .[128X[104X
    [4X[28X . . . . . . . . . . 1 1 . . . . . . . .[128X[104X
    [4X[28X . . . . . . . . . . 1 1 . . . . . . . .[128X[104X
    [4X[28X . . . . . . . . . . . . 1 1 . . . . . .[128X[104X
    [4X[28X . . . . . . . . . . . . 1 1 . . . . . .[128X[104X
    [4X[28X . . . . . . . . . . . . . . 1 1 . . . .[128X[104X
    [4X[28X . . . . . . . . . . . . . . 1 1 . . . .[128X[104X
    [4X[28X . . . . . . . . . . . . . . . . 1 1 . .[128X[104X
    [4X[28X . . . . . . . . . . . . . . . . 1 1 . .[128X[104X
    [4X[28X . . . . . . . . . . . . . . . . . . 1 1[128X[104X
    [4X[28X . . . . . . . . . . . . . . . . . . 1 1[128X[104X
    [4X[25Xgap>[125X [27XRank(M);[127X[104X
    [4X[28X10[128X[104X
  [4X[32X[104X
  
