From 976efe0e08824f71108e7f2f0e62d473851d7dde Mon Sep 17 00:00:00 2001
From: Paul Koch <code@koch.ninja>
Date: Wed, 15 Jan 2025 01:50:48 -0800
Subject: [PATCH] disable non-IEEE 754 math

---
 build.sh                                             | 2 +-
 python/interpret-core/tests/glassbox/ebm/test_ebm.py | 5 +----
 shared/libebm/interpretable_numerics.cpp             | 6 +++++-
 3 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/build.sh b/build.sh
index dc43b8646..36989946f 100644
--- a/build.sh
+++ b/build.sh
@@ -413,7 +413,7 @@ all_args="$all_args -Wformat=2"
 all_args="$all_args -Wno-format-nonliteral"
 all_args="$all_args -Wno-parentheses"
 all_args="$all_args -fvisibility=hidden -fvisibility-inlines-hidden"
-all_args="$all_args -fno-math-errno -fno-trapping-math"
+all_args="$all_args -fno-math-errno -fno-trapping-math -fno-fast-math -ffp-contract=off"
 # TODO: once we have highly efficient tightly looped code, try no -fpic and see if that makes better code.  The compiler can save a register in this case. See https://akkadia.org/drepper/dsohowto.pdf
 # TODO: check no-plt compiler option
 all_args="$all_args -fpic"
diff --git a/python/interpret-core/tests/glassbox/ebm/test_ebm.py b/python/interpret-core/tests/glassbox/ebm/test_ebm.py
index f746563a0..af9f77f82 100644
--- a/python/interpret-core/tests/glassbox/ebm/test_ebm.py
+++ b/python/interpret-core/tests/glassbox/ebm/test_ebm.py
@@ -1245,9 +1245,6 @@ def test_replicatability_classification():
             break
 
 
-@pytest.mark.skip(
-    reason="Fails on mac. Need to work on getting cross platform identical results."
-)
 def test_identical_classification():
     from interpret.develop import get_option, set_option
 
@@ -1271,7 +1268,7 @@ def test_identical_classification():
             pred = ebm.eval_terms(X)
             total += np.sum(pred)
 
-        expected = 2.220446049250313e-15
+        expected = -3.941291737419306e-15
         if total != expected:
             assert total == expected
             break
diff --git a/shared/libebm/interpretable_numerics.cpp b/shared/libebm/interpretable_numerics.cpp
index 947a0ad5e..29383a480 100644
--- a/shared/libebm/interpretable_numerics.cpp
+++ b/shared/libebm/interpretable_numerics.cpp
@@ -1379,6 +1379,9 @@ static double Mean(const size_t cSamples,
    // https://stackoverflow.com/questions/895929/how-do-i-determine-the-standard-deviation-stddev-of-a-set-of-values
    // https://www.johndcook.com/blog/standard_deviation/
 
+   // do not put multiple floating point operations in the same statement since that can be optimized
+   // https://clang.llvm.org/docs/UsersManual.html
+
    double factor = 1.0;
    double mean;
    size_t cNaN;
@@ -1440,7 +1443,8 @@ static double Mean(const size_t cSamples,
                // if all the weights are zero, then weigh them all equally
                ratio = double{1} / static_cast<double>(cNormal);
             }
-            mean += numerator * ratio;
+            const double multiple = numerator * ratio;
+            mean += multiple;
          }
          if(nullptr != pWeight) {
             ++pWeight;