From: trevor_hansen <trevor_hansen@e59a4935-1847-0410-ae03-e826735625c1>
Date: Tue, 10 Apr 2012 04:54:59 +0000 (+0000)
Subject: Improvement. A simplified trailing zeroes propagator.
X-Git-Url: https://git.unchartedbackwaters.co.uk/w/?a=commitdiff_plain;h=514515ddf5c8083e2227e30d84bbbb67d5a184b9;p=francis%2Fstp.git

Improvement. A simplified trailing zeroes propagator.

git-svn-id: https://stp-fast-prover.svn.sourceforge.net/svnroot/stp-fast-prover/trunk/stp@1636 e59a4935-1847-0410-ae03-e826735625c1
---

diff --git a/src/simplifier/constantBitP/ConstantBitP_Multiplication.cpp b/src/simplifier/constantBitP/ConstantBitP_Multiplication.cpp
index 81fd383..5662ac4 100644
--- a/src/simplifier/constantBitP/ConstantBitP_Multiplication.cpp
+++ b/src/simplifier/constantBitP/ConstantBitP_Multiplication.cpp
@@ -273,9 +273,49 @@ namespace simplifier
       return NOT_IMPLEMENTED;
     }
 
+    Result
+    trailingOneReasoning_OLD(FixedBits& x, FixedBits&y, FixedBits& output);
+
+
+    // Remove from x any trailing "boths", that don't have support in y and output.
+        Result
+        trailingOneReasoning(FixedBits& x, FixedBits&y, FixedBits& output)
+        {
+          Result r = NO_CHANGE;
+
+          const int bitwidth = output.getWidth();
+
+          const int y_min = y.minimum_trailingOne();
+          const int y_max = y.maximum_trailingOne();
+
+          const int output_max = output.maximum_trailingOne();
+
+          for (int i = 0; i < bitwidth; i++)
+            {
+            if (x[i] == '0')
+              continue;
+
+            if (x[i] == '1')
+              break;
+
+            for (int j = y_min; j <= std::min(y_max, output_max); j++)
+              {
+                if (j + i >= bitwidth || (y[j] != '0' && output[i + j] != '0'))
+                  return r;
+              }
+
+              x.setFixed(i, true);
+              x.setValue(i, false);
+              r = CHANGED;
+            }
+
+          assert(trailingOneReasoning_OLD(x,y,output) == NO_CHANGE);
+          return r;
+        }
+
 // Remove from x any trailing "boths", that don't have support in y and output.
     Result
-    trailingOneReasoning(FixedBits& x, FixedBits&y, FixedBits& output)
+    trailingOneReasoning_OLD(FixedBits& x, FixedBits&y, FixedBits& output)
     {
       Result r = NO_CHANGE;