Re: [Help-glpk] inf as RHS of constraint

[glpk xypron]

Hello Kevin, hello Andrew,

> > Which version of GLPK have you been using? GLPK 4.45 should support
> > inf and infinity.
> 

the following patch should resolve the issue.

Best regards

Xypron

--- glpk-4.45\src\glpcpx.c      2010-12-05 10:00:00.000000000 +0100
+++ glpk-4.45\src\glpcpx.c      2011-01-18 15:46:36.426163500 +0100
@@ -523,8 +523,9 @@
 *
 *  <row name> ::= <empty> | <symbolic name> :
 *  <row sense> ::= < | <= | =< | > | >= | => | =
+*  <infinity> ::= infinity | inf
 *  <right-hand side> ::= <numeric constant> | + <numeric constant> |
-*     - <numeric constant>
+*     - <numeric constant> | + <infinity> | - <infinity>
 *  <constraint> ::= <row name> <linear form> <row sense>
 *     <right-hand side>
 *  <subject to> ::= subject to | such that | st | s.t. | st.
@@ -575,9 +576,20 @@
          s = -1.0, scan_token(csa);
       else
          s = +1.0;
-      if (csa->token != T_NUMBER)
-         error(csa, "missing right-hand side\n");
-      glp_set_row_bnds(csa->P, i, type, s * csa->value, s * csa->value);
+      if (csa->token == T_NUMBER)
+      {  glp_set_row_bnds(csa->P, i, type, s * csa->value, s * csa->value);
+      } else if (the_same(csa->image, "infinity") ||
+                 the_same(csa->image, "inf"))
+      {  if ( s > 0 && type != GLP_UP ) 
+         {  error(csa, "invalid use of `inf' as lower bound\n");
+         } else if ( s < 0 && type != GLP_LO )
+         {  error(csa, "invalid use of `-inf' as upper bound\n");
+         } else
+         {  glp_set_row_bnds(csa->P, i, type, s * DBL_MAX, s * DBL_MAX );
+         }
+      } else
+      { error(csa, "missing right-hand side\n");
+      }
       /* the rest of the current line must be empty */
       if (!(csa->c == '\n' || csa->c == XEOF))
          error(csa, "invalid symbol(s) beyond right-hand side\n");

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