|  |  D.7.5.1 prepMat Procedure from librarystratify.lib(see  stratify_lib).
 
Example:Usage:
prepMat(M,wr,ws,step);
where M is a matrix, wr is an intvec of size ncols(M),
ws an intvec of size nrows(M) and step is an integer
 
Return:
2 lists of submatrices corresponding to the filtrations
specified by wr and ws:
the first list corresponds to the list for the filtration
of AdA, i.e. the ranks of these matrices will be the r_i,
the second one to the list for the filtration of L, i.e.
the ranks of these matrices will be the s_i
 
Note:
* the entries of the matrix M are M_ij=delta_i(x_j),
* wr is used to determine what subset of the set of all dx_i is
generating AdF^l(A):
 if (k-1)*step <= wr[i] < k*step, then dx_i is in the set of
generators of AdF^l(A) for all l>=k and the i-th column
of M appears in each submatrix starting from the k-th
 * ws is used to determine what subset of the set of all delta_i
is generating Z_l(L):
 if (k-1)*step <= ws[i] < k*step, then delta_i is in the set
of generators of Z_l(A) for l < k and the i-th row of M
appears in each submatrix up to the (k-1)th
 * the entries of wr and ws as well as step should be positive
integers
 
 |  | LIB "stratify.lib";
ring r=0,(t(1..3)),dp;
matrix M[2][3]=0,t(1),3*t(2),0,0,t(1);
print(M);
==> 0,t(1),3*t(2),
==> 0,0,   t(1)   
intvec wr=1,3,5;
intvec ws=2,4;
int step=2;
prepMat(M,wr,ws,step);
==> [1]:
==>    [1]:
==>       _[1,1]=0
==>       _[2,1]=0
==>    [2]:
==>       _[1,1]=0
==>       _[1,2]=t(1)
==>       _[2,1]=0
==>       _[2,2]=0
==>    [3]:
==>       _[1,1]=0
==>       _[1,2]=t(1)
==>       _[1,3]=3*t(2)
==>       _[2,1]=0
==>       _[2,2]=0
==>       _[2,3]=t(1)
==> [2]:
==>    [1]:
==>       _[1,1]=0
==>       _[1,2]=t(1)
==>       _[1,3]=3*t(2)
==>       _[2,1]=0
==>       _[2,2]=0
==>       _[2,3]=t(1)
==>    [2]:
==>       _[1,1]=0
==>       _[1,2]=0
==>       _[1,3]=t(1)
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