[m-rev.] diff: debugging code for fourier elimination

[Julien Fischer]

The following is intended as a source of problems for Thibault,
so he can experiment with his implementation of Fourier
elimination in G12.

Estimated hours taken: 0.1
Branches: main

Add some debugging code to Fourier elimination implementation
used by the termination analyser.

compiler/lp_rational.m:
 	Add code inside a trace goal that allows the constraint
 	systems passed to Fourier elimination to be dumped to
 	stdout.

Julien.

Index: compiler/lp_rational.m
===================================================================
RCS file: /home/mercury/mercury1/repository/mercury/compiler/lp_rational.m,v
retrieving revision 1.8
diff -u -r1.8 lp_rational.m
--- compiler/lp_rational.m	1 Dec 2006 15:04:04 -0000	1.8
+++ compiler/lp_rational.m	13 Dec 2006 02:33:00 -0000
@@ -1445,8 +1445,24 @@
          % Skip the call to fourier_elimination/6 if there are no variables to
          % project - this avoids the transformation to vector form.
          %
-        ( !.Vars \= [] ->
+        ( 
+            !.Vars = [_ | _],
              Matrix0 = constraints_to_matrix(Constraints1), 
+            trace [
+                compile_time(flag("debug_fourier_elim")),
+                run_time(env("MC_DUMP_FOURIER_ELIM")),
+                io(!IO)
+            ] (
+                io.write_string("------------------------------------\n", !IO),
+                io.write_string("Matrix passed to fourier_elimination/6\n",
+                    !IO),
+                write_matrix(Varset, no, Matrix0, !IO),
+                io.nl(!IO),
+                io.write_string("Variables to project:\n", !IO),
+                write_vars(Varset, !.Vars, !IO),
+                io.nl(!IO),
+                io.write_string("------------------------------------\n", !IO)
+            ),
              fourier_elimination(!.Vars, Varset, MaybeThreshold, 0,
                  Matrix0, FourierResult),
              (
@@ -1463,6 +1479,7 @@
              % would mean traversing the matrix, so we wait until the next
              % operation that needs to traverse it anyway or until the
              % next entailment check.
+            !.Vars = [],
              Result = ok(Constraints1)
          )
      ).
@@ -1720,10 +1737,13 @@
      ;
          NewMatrix = yes(ZeroMatrix)
      ),
-    ( if    NewMatrix = yes(Matrix)
-      then  fourier_elimination(OtherVars, Varset, MaybeThreshold, !.Step, 
+    ( 
+        NewMatrix = yes(Matrix),
+        fourier_elimination(OtherVars, Varset, MaybeThreshold, !.Step,
              Matrix, Result)
-      else  Result = no
+    ;
+        NewMatrix = no,
+        Result = no
      ).

      % separate_vectors(Matrix, Var, Positive, Negative, Zero, Num).
@@ -2309,7 +2329,7 @@

  :- func var_to_string(lp_varset, lp_var) = string.

-var_to_string(Varset, Var) = varset.lookup_name(Varset, Var, "Unnamed").
+var_to_string(Varset, Var) = varset.lookup_name(Varset, Var).

      % Write out the matrix used during fourier elimination.  If
      % `Labels' is `yes' then write out the label for each vector

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