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Re: [Help-glpk] Basis read/write
From: |
prem swaroop |
Subject: |
Re: [Help-glpk] Basis read/write |
Date: |
Mon, 26 Oct 2009 03:35:02 +0300 |
Thanks Dave.
In the hope of achieving the same, I found and tried -w and -r options
documented thus in version 4.39:
-r filename, --read filename
read solution from filename rather to find it with
the solver
-w filename, --write filename
write solution to filename in plain text format
However, after -r, the solver does not solve the problem at all (despite my
specifying --min just to try). This is consistent to documentation for sure.
I am unsure how far this can go - but there apparently are APIs that do these
jobs, we only need their equivalent command-line versions:
3.3.2 glp read sol—read basic solution from text file
Description
The routine glp_read_sol reads basic solution from a text file whose name
is specified by the parameter fname into the problem object.
For the file format see description of the routine glp_write_sol.
3.3.3 glp write sol—write basic solution to text file
Description
The routine glp_write_sol writes the current basic solution to a text file
whose name is specified by the parameter fname. This file can be read back
with the routine glp_read_sol.
Thanks for a great work!
Regards
Prem
On Sun, Oct 25, 2009 at 12:31 PM, David Posner <address@hidden> wrote:
Hi Prem, I don #39;t have an answer but I asked about a few months ago in
connection with a port I was trying to do from a commercial LP solver which
supports saving/restoring bases from files and I never got an answer. Anyway I
second your request!
Dave Posner
----- Original Message ----
From: prem swaroop <address@hidden>
To: address@hidden
Sent: Sunday, October 25, 2009 5:08:46 AM
Subject: [Help-glpk] Basis read/write
Team
There #39;s a couple of features documented in 4.34 in the stand-alone solver
section (Appendix D):
(Options specific to simplex method)
--bas filename read initial basis from filename in MPS format
--wbas filename write nal basis to filename in MPS format
Both are missing from the glpsol that I built on cygwin/Windows Vista, for
versions 4.34 as well as 4.39.
Now, documentation for 4.39 does NOT mention these features - so that #39;s at
least consistent.
I suspect this feature existed earlier on. I think this could be a useful
feature to keep, and I can quote my case here.
I am essentially solving a large-ish LP whose parameters are generated by
incrementing one parameter value. And so, I dont expect too many changes in
the solution for a large part of my increments, and hence using a final basis
for one solution as an initial basis for the next could save a lot in time.
Regards
Prem
Thanks Dave.
In the hope of achieving the same, I found and tried -w and -r options documented thus in version 4.39:
-r filename, --read filename
read solution from filename rather to find it with
the solver
-w filename, --write filename
write solution to filename in plain text format
However, after -r, the solver does not solve the problem at all (despite my specifying --min just to try). This is consistent to documentation for sure.
I am unsure how far this can go - but there apparently are APIs that do these jobs, we only need their equivalent command-line versions:
3.3.2 glp read solread basic solution from text file
Description
The routine glp_read_sol reads basic solution from a text file whose name
is specified by the parameter fname into the problem object.
For the file format see description of the routine glp_write_sol.
3.3.3 glp write solwrite basic solution to text file
Description
The routine glp_write_sol writes the current basic solution to a text file
whose name is specified by the parameter fname. This file can be read back
with the routine glp_read_sol.
Thanks for a great work!
Regards
Prem
On Sun, Oct 25, 2009 at 12:31 PM, David Posner
<address@hidden> wrote:
Hi Prem, I don't have an answer but I asked about a few months ago in connection with a port I was trying to do from a commercial LP solver which supports saving/restoring bases from files and I never got an answer. Anyway I second your request!
Dave Posner
----- Original Message ----
From: prem swaroop <address@hidden>
To: address@hidden
Sent: Sunday, October 25, 2009 5:08:46 AM
Subject: [Help-glpk] Basis read/write
Team
There #39;s a couple of features documented in 4.34 in the stand-alone solver section (Appendix D):
(Options specific to simplex method)
--bas filename read initial basis from filename in MPS format
--wbas filename write nal basis to filename in MPS format
Both are missing from the glpsol that I built on cygwin/Windows Vista, for versions 4.34 as well as 4.39.
Now, documentation for 4.39 does NOT mention these features - so that #39;s at least consistent.
I suspect this feature existed earlier on. I think this could be a useful feature to keep, and I can quote my case here.
I am essentially solving a large-ish LP whose parameters are generated by incrementing one parameter value. And so, I dont expect too many changes in the solution for a large part of my increments, and hence using a final basis for one solution as an initial basis for the next could save a lot in time.
Regards
Prem