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Optimization constraints
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<TR><TD><FONT SIZE=4><B><A NAME="htoc338">8.10</A></B></FONT></TD>
<TD WIDTH="100%" ALIGN=center><FONT SIZE=4><B>Optimization constraints</B></FONT></TD>
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<LI><A HREF="manual064.html#toc276"> <TT>fd_minimize/2</TT>,
<TT>fd_maximize/2</TT></A>
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<TR><TD><B><A NAME="htoc339">8.10.1</A></B></TD>
<TD WIDTH="100%" ALIGN=center><B><TT>fd_minimize/2</TT>,
<TT>fd_maximize/2</TT></B></TD>
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<B>Templates</B>
<DL COMPACT=compact><DT><DD><TT>
fd_minimize(+callable_term, ?fd_variable)<BR>
fd_maximize(+callable_term, ?fd_variable)</TT></DL>
<B>Description</B><BR>
<BR>
<TT>fd_minimize(Goal, X)</TT> repeatedly calls <TT>Goal</TT> to find a
value that minimizes the variable <TT>X</TT>. <TT>Goal</TT> is a Prolog goal
that should instantiate <TT>X</TT>, a common case being the use of
<TT>fd_labeling/2</TT> (section <A HREF="manual063.html#fd-labeling/2">8.9.1</A>). This predicate uses a
branch-and-bound algorithm with restart: each time <TT>call(Goal)</TT>
succeeds the computation restarts with a new constraint <TT>X #< V</TT>
where <TT>V</TT> is the value of <TT>X</TT> at the end of the last call of
<TT>Goal</TT>. When a failure occurs (either because there are no remaining
choice-points for <TT>Goal</TT> or because the added constraint is
inconsistent with the rest of the store) the last solution is recomputed
since it is optimal.<BR>
<BR>
<TT>fd_maximize(Goal, X)</TT> is similar to <TT>fd_minimize/2</TT> but
<TT>X</TT> is maximized<TT>.</TT><BR>
<BR>
<B>Errors</B><BR>
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<TR><TD VALIGN=top ALIGN=left><TT>Goal</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP> </TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
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<TR><TD VALIGN=top ALIGN=left><TT>Goal</TT> is neither a variable nor a callable term</TD>
<TD VALIGN=top ALIGN=center NOWRAP> </TD>
<TD VALIGN=top ALIGN=left><TT>type_error(callable, Goal)</TT></TD>
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<TR><TD VALIGN=top ALIGN=left>The predicate indicator <TT>Pred</TT> of <TT>Goal</TT> does not
correspond to an existing procedure and the value of the <TT>unknown</TT>
Prolog flag is <TT>error</TT> (section <A HREF="manual045.html#set-prolog-flag/2">7.22.1</A>)</TD>
<TD VALIGN=top ALIGN=center NOWRAP> </TD>
<TD VALIGN=top ALIGN=left><TT>existence_error(procedure, Pred)</TT></TD>
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<TR><TD VALIGN=top ALIGN=left><TT>X</TT> is neither a variable nor an FD variable nor an integer
</TD>
<TD VALIGN=top ALIGN=center NOWRAP> </TD>
<TD VALIGN=top ALIGN=left><TT>type_error(fd_variable, X)</TT></TD>
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<B>Portability</B><BR>
<BR>
GNU Prolog predicates.
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