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Re: [Help-glpk] Problem : basis
From: |
Cedric[FR] |
Subject: |
Re: [Help-glpk] Problem : basis |
Date: |
Fri, 8 Jun 2007 13:36:31 +0400 |
I understand the column status.
For row, if I understood well, the row is active if Ax=b
for the problem Ax<=b with x auxiliary variables. So, structural variables =
0
my algorithm is:
->solve problem
->delete columns and rows
->add columns
->resolve problem
But, if I delete column or rows, I must to have a basis solution to resolve
my problem.
So I must resolve my problem after fix the column status
my algorithm become:
->solve problem
->change status
->resolve problem
->delete columns and rows
->add columns
->resolve problem
Andrew Makhorin wrote:
>
>> Yes, I delete Rows and Cols
>
> If the current basis is valid (whether optimal or not) and if you
> delete active rows (i.e. the rows for which glp_get_row_stat returns
> GLP_NL, GLP_NU, GLP_NF, or GLP_NS) and/or basic columns (i.e. the
> columns for which glp_get_col_stat returns GLP_BS), the basis becomes
> invalid. To keep it valid you either have not to delete such rows or
> columns or have to change the statuses of remaining rows and columns
> appropriately.
>
>> For Row, must I use glp_set_row_stat(lp , i , GLP_NL)?
>
>> For Column, must I use glp_set_col_stat(lp , i , GLP_NL)?
>
> Do you understand what is the row/column status?
>
>> How can I fix my column at 0?
>
> glp_set_col_bnds(lp, j, GLP_FX, 0.0, 0.0);
>
>> must I resolve my problem before to add column or row?
>
>> Or
>
>> must I only start again the routine lpx_std_basis(lp)?
>
> lpx_std_basis makes all auxiliary variables basic and all structural
> variables non-basic, i.e. using it you lose all the current basis
> information.
>
>
>
>
>
> _______________________________________________
> Help-glpk mailing list
> address@hidden
> http://lists.gnu.org/mailman/listinfo/help-glpk
>
>
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