From 014777a816991682748e500dc1e5de7e844c7d3e Mon Sep 17 00:00:00 2001
From: Greg Carl <26096779+snowgoer540@users.noreply.github.com>
Date: Sat, 17 Jun 2023 11:49:28 -0400
Subject: [PATCH] interp: fix GE/LE operators to better handle double-precision
 comparison

This commit does four things:
1. Changes the LE/GE operators to better handle double-precision
floating-point comparisons. When comparing two values as equal (or not
equal) the EQ and NE operators considered the floating-point precision
"issue" by comparing the difference between the two values to
TOLERANCE_EQUAL, GE and LE did not.
2. Tidy the difference by using fabs()
3. Modify the TOLERANCE_EQUAL threshold to 1e-6.  Previously this was
set to .0001 which is very close to a reasonable difference between two
gcode coordinate values.
4. Update the documentation to reflect these change.
---
 docs/src/gcode/overview.adoc        |  9 ++++-----
 src/emc/rs274ngc/interp_execute.cc  | 12 ++++++------
 src/emc/rs274ngc/interp_internal.hh |  4 ++--
 3 files changed, 12 insertions(+), 13 deletions(-)

diff --git a/docs/src/gcode/overview.adoc b/docs/src/gcode/overview.adoc
index 6d8a1e7ac8f..de07e876dc9 100644
--- a/docs/src/gcode/overview.adoc
+++ b/docs/src/gcode/overview.adoc
@@ -704,11 +704,10 @@ false, and any non-zero number is equivalent to logical true.
 
 == Equality and floating-point values
 
-The RS274/NGC language only supports floating-point values of finite
-precision. Therefore, testing for equality or inequality of two
-floating-point values is inherently problematic. The interpreter
-solves this problem by considering values equal if their absolute
-difference is less than 0.0001 (this value is defined as
+Testing for equality or inequality of two
+double-precision floating-point values is inherently problematic.
+The interpreter solves this problem by considering values equal if
+their absolute difference is less than 1e-6 (this value is defined as
 'TOLERANCE_EQUAL' in src/emc/rs274ngc/interp_internal.hh).
 
 [[gcode:functions]]
diff --git a/src/emc/rs274ngc/interp_execute.cc b/src/emc/rs274ngc/interp_execute.cc
index 7897ba7ae48..4e0367f8467 100644
--- a/src/emc/rs274ngc/interp_execute.cc
+++ b/src/emc/rs274ngc/interp_execute.cc
@@ -158,20 +158,20 @@ int Interp::execute_binary2(double *left,        //!< pointer to the left operan
       *left = (*left < *right) ? 1.0 : 0.0;
       break;
   case EQ:
-      diff = *left - *right;
-      diff = (diff < 0) ? -diff : diff;
+      diff = fabs(*left - *right);
       *left = (diff < TOLERANCE_EQUAL) ? 1.0 : 0.0;
       break;
   case NE:
-      diff = *left - *right;
-      diff = (diff < 0) ? -diff : diff;
+      diff = fabs(*left - *right);
       *left = (diff >= TOLERANCE_EQUAL) ? 1.0 : 0.0;
       break;
   case LE:
-      *left = (*left <= *right) ? 1.0 : 0.0;
+      diff = fabs(*left - *right);
+      *left = ((diff < TOLERANCE_EQUAL) || (*left <= *right)) ? 1.0 : 0.0;
       break;
   case GE:
-      *left = (*left >= *right) ? 1.0 : 0.0;
+      diff = fabs(*left - *right);
+      *left = ((diff < TOLERANCE_EQUAL) || (*left >= *right)) ? 1.0 : 0.0;
       break;
   case GT:
       *left = (*left > *right) ? 1.0 : 0.0;
diff --git a/src/emc/rs274ngc/interp_internal.hh b/src/emc/rs274ngc/interp_internal.hh
index 15092fa75ba..99547e3db0e 100644
--- a/src/emc/rs274ngc/interp_internal.hh
+++ b/src/emc/rs274ngc/interp_internal.hh
@@ -87,8 +87,8 @@ Tighter tolerance down to a minimum of 1 micron +- also accepted.
 #define SPIRAL_RELATIVE_TOLERANCE 0.001
 
 /* angle threshold for concavity for cutter compensation, in radians */
-#define TOLERANCE_CONCAVE_CORNER 0.05  
-#define TOLERANCE_EQUAL 0.0001 /* two numbers compare EQ if the
+#define TOLERANCE_CONCAVE_CORNER 0.05
+#define TOLERANCE_EQUAL 1e-6 /* two numbers compare EQ if the
 				  difference is less than this */
 
 static inline bool equal(double a, double b)