From cfc7b0d2d4c58051565f965d558221cbd5c6eea9 Mon Sep 17 00:00:00 2001
From: Ceriel Jacobs <c.j.h.jacobs@vu.nl>
Date: Tue, 22 Nov 2022 09:36:43 +0100
Subject: [PATCH] Addressing issue #64 and issue #98: rewrite existential
 multi-head rules

---
 src/vlog/common/concepts.cpp    |  8 +++++++-
 src/vlog/forward/seminaiver.cpp | 16 +++++++++-------
 2 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/src/vlog/common/concepts.cpp b/src/vlog/common/concepts.cpp
index 2458e022..08eb41f1 100644
--- a/src/vlog/common/concepts.cpp
+++ b/src/vlog/common/concepts.cpp
@@ -1325,7 +1325,13 @@ void Program::addRule(std::vector<Literal> heads, std::vector<Literal> body,
         rewriteRule(heads, body);
     } else {
         Rule rule(allrules.size(), heads, body, isEGD);
-        addRule(rule);
+        if (heads.size() > 1 && rule.isExistential()) {
+            // Work-around for bug in existential multihead rules, github issue #98 and issue #64.
+            // Easiest fix is to just rewrite these rules.
+            rewriteRule(heads, body);
+        } else {
+            addRule(rule);
+        }
     }
 }
 
diff --git a/src/vlog/forward/seminaiver.cpp b/src/vlog/forward/seminaiver.cpp
index ad8f5a05..b691a40c 100644
--- a/src/vlog/forward/seminaiver.cpp
+++ b/src/vlog/forward/seminaiver.cpp
@@ -1831,14 +1831,16 @@ void SemiNaiver::printCountAllIDBs(std::string prefix) {
     for (PredId_t i = 0; i < program->getNPredicates(); ++i) {
         if (predicatesTables[i] != NULL) {
             if (program->isPredicateIDB(i)) {
-                size_t count = predicatesTables[i]->getNAllRows();
-                if (count == 0) {
-                    emptyRel++;
-                }
                 std::string predname = program->getPredicateName(i);
-                LOG(DEBUGL) << prefix << "Cardinality of " <<
-                    predname << ": " << count;
-                c += count;
+                if (predname.rfind("__Generated", 0) != 0) {
+                    // Only count original predicates.
+                    size_t count = predicatesTables[i]->getNAllRows();
+                    LOG(DEBUGL) << prefix << "Cardinality of " << predname << ": " << count;
+                    if (count == 0) {
+                        emptyRel++;
+                    }
+                    c += count;
+                }
             }
         }
     }