[Help-glpk] lp/mip problem data in dimacs-like format

[Andrew Makhorin]

Below here is a draft description of dimacs-like format to represent
lp/mip problem data. Text files in this format are human-readable and
suitable for processing with text tools like sed, gawk, etc., so this
format can be used in glpk as a basic low-level format.

Any comments are appreciated. Thanks.

Andrew Makhorin



LP/MIP problem data in DIMACS-like format
*****************************************

Comment line
------------
c arbitrary text

Problem descriptor line
-----------------------
p lp ROWS COLS NONZ           LP problem
p mip ROWS COLS NONZ          MIP problem

ROWS is the number of rows
COLS is the number of columns
NONZ is the number of non-zero constraint coefficients

Row descriptor line
-------------------
r ROW f                       free (unbounded) row
r ROW l RHS                   inequality of '>=' type
r ROW u RHS                   inequality of '<=' type
r ROW d RHS1 RHS2             double-sided inequality
r ROW s RHS                   equality

ROW is row ordinal number (1 to ROWS)
RHS is right-hand side

Column descriptor line
----------------------
x COL f                       free (unbounded) column
x COL l BND                   column with (non-zero) lower bound
x COL u BND                   column with upper bound
x COL d BND1 BND2             double-bounded column
x COL s BND                   fixed column

COL is column ordinal number (1 to COLS)
BND is column bound/fixed value

Column kind descriptor line (ignored for LP)
--------------------------------------------
k COL c                       continuous column (default)
k COL i                       integer column
k COL b                       binary column

COL is column ordinal number (1 to COLS)

Objective/constraint coefficient descriptor line
------------------------------------------------
a 0 COL COEF                  objective coefficient
a ROW COL COEF                constraint coefficient

ROW is row ordinal number (1 to ROWS)
COL is column ordinal number (1 to COLS)
COEF is (non-zero) coefficient value

Symbolic name descriptor line
-----------------------------
n p NAME                      problem name
n z NAME                      objective function name
n r ROW NAME                  row name
n x COL NAME                  column name

ROW is row ordinal number (1 to ROWS)
COL is column ordinal number (1 to COLS)
NAME is symbolic name (1 to 255 chars)