RE: [Fwd: Discussion on GLPK]

[Meketon, Marc]

Hello Mingyue,

Typically when I see that many coefficients, it suggests that you need to 
reformulate your problem.

One example.  Suppose that X1, X2, X3, …, X20 are non-negative integers, and 
you have equations like X1 <= b1, X1 + X2 <= b2, X1 + X2 + X3 <= b3, …, X1 + X2 
+ X3 + … + X20 <= b20.  That has 20*(20+1)/2 = 210 coefficients

A reformulation would be to introduce variables Y1, Y2, Y3, …, Y20, then you 
could write Y1 = X1, Y2 = Y1 + X2, Y3 = Y2 + X3, … , Y20 = Y19 + X20, and have 
the Y’s have upper bounds: Y1 <= b1, Y2 <=  b2.  That’s 59 coefficients.

-Marc

From: Help-glpk  On 
Behalf Of Andrew Makhorin
Sent: Tuesday, April 19, 2022 7:20 AM
To: help-glpk@gnu.org
Subject: [Fwd: Discussion on GLPK]

 Forwarded Message 

Date: Tue, 19 Apr 2022 10:00:54 +0800
Subject: Discussion on GLPK
To: help-glpk@gnu.org
From: jimingyue 
<20s103...@stu.hit.edu.cn>
Dear developer,
Hope you are well!
Recently, I use GLPK to solve a LP problem in my graduation project. My 
coefficient matrix is very large so that there is a bug “glp_load_matrix: 
ne=1889848940; too many constraint coefficients”. I google this hint and find 
GLPK requires the size of coefficient matrix is less than 5.  So I have 
two questions as follows,

1. Why the size is required less than 5?

2. If I cannot limit the size within 5, is there some way to solve 
my LP problem using GLPK? If the answer is yes, do I need to modify any code? ? 
If the answer is no, could you give me some advices to solve my problem?
Looking forward to your reply!
Really appreciate your help!
Best regards,
Mingyue Ji


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[Fwd: Discussion on GLPK]

[Andrew Makhorin]

 Forwarded Message 
Date: Tue, 19 Apr 2022 10:00:54 +0800Subject: Discussion on GLPKTo: help
-glpk@gnu.orgFrom: jimingyue <20s103...@stu.hit.edu.cn>Dear developer,
Hope you are well!
Recently, I use GLPK to solve a LP problem in my graduation project. My
coefficient matrix is very large so that there is a bug
“glp_load_matrix: ne=1889848940; too many constraint coefficients”. I
google this hint and find GLPK requires the size of coefficient matrix
is less than 5.  So I have two questions as follows,
1. Why the size is required less than 5?
2. If I cannot limit the size within 5, is there some way to
solve my LP problem using GLPK? If the answer is yes, do I need to
modify any code? ? If the answer is no, could you give me some advices
to solve my problem?
Looking forward to your reply!
Really appreciate your help!
Best regards,
Mingyue Ji