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Re: [Help-glpk] proposal for gnu lp/mip low-level format

From: Brady Hunsaker
Subject: Re: [Help-glpk] proposal for gnu lp/mip low-level format
Date: Thu, 22 Jul 2004 10:18:17 -0400

This is certainly better than MPS format and is consistent with some
other common low-level formats.  The ability to give row and column
names is good.

The one thing I would add is some guidelines about precision and
numerical formats.  Is arbitrary precision allowed in the numbers?  I
guess the idea would be that numbers would be rounded (as always) to fit
in whatever floating-point data type that a solver uses, but with no
predefined precision limit in the file.  Therefore it is possible that
different solvers would round input differently if they use different
floating-point data types.

Also, I would perhaps make it explicit that various notations are

What about slightly odd notations?
2.3e0004   (lots of unnecessary digits in the exponent)
231.3e7    (abnormal use of exponent)

Are real number input formats standardized anywhere?  I have a sense of
what's "normal" and what isn't, but I don't know if it's written down
anywhere.  This is important because we don't want some parsers to fail
on certain input files just because they disagreed on whether a format
was acceptable.


On Wed, 2004-07-21 at 21:30, Andrew Makhorin wrote:
> I propose a (GNU) low-level format for coding lp/mip instances. Below
> here is its brief description. I would appreciate any suggestions.
> Andrew Makhorin
> It is a text format. The file may contain the following lines:
> * comment
> N problem-name
> P problem-class objective-sense num-rows num-cols num-nz
> R row-num F
> R row-num L lower-bound
> R row-num U upper-bound
> R row-num D lower-bound upper-bound
> R row-num S fixed-value
> C col-num F
> C col-num L lower-bound
> C col-num U upper-bound
> C col-num D lower-bound upper-bound
> C col-num S fixed-value
> F col-num objective_coef
> F 0 constant-term
> A row-num col-num constraint-coefficient
> I row-num row-name
> J col-num col-name
> E O F
> All lines, except P-line and E-line, are optional and may follow in
> arbitrary order.

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