From: Matthias Maier <tamiko@43-1.org>
Date: Fri, 5 Apr 2024 19:57:13 +0000 (-0500)
Subject: Test: cgal/cgal_mesh_criteria: disable floating point exceptions
X-Git-Tag: v9.6.0-rc1~399^2
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=377b23e009792094e805eef477b0a0a412a17678;p=dealii.git

Test: cgal/cgal_mesh_criteria: disable floating point exceptions

We trigger a (deliberate) floating point exception in the CGAL (header)
library:
```
    // The multiplications could produce some NaN, with 0 * inf. Replacing it with inf is safe.
    // min(x,y) (the order is essential) returns its second argument when the first is NaN.
    // An IEEE 754-2019 maximum could help.
    __m128d big = IA::largest().simd();
->  __m128d x1 = _mm_mul_pd(aa,bz);                       // {-ai*bi,as*bs}
    //x1 = _mm_min_pd(x1,big); // no NaN
    __m128d x2 = _mm_mul_pd(aa,c);                        // {-ai*bs,as*bi}
    x2 = _mm_min_pd(x2,big); // no NaN
    __m128d x3 = _mm_mul_pd(ap,bz);                       // {-as*bi,ai*bs}
    //x3 = _mm_min_pd(x3,big); // no NaN
    __m128d x4 = _mm_mul_pd(ap,c);                        // {-as*bs,ai*bi}
    x4 = _mm_min_pd(x4,big); // no NaN
```

Thus, disable floating point exceptions for the test.
---

diff --git a/tests/cgal/cgal_mesh_criteria.cc b/tests/cgal/cgal_mesh_criteria.cc
index 3ecde4ba7e..f150f591b5 100644
--- a/tests/cgal/cgal_mesh_criteria.cc
+++ b/tests/cgal/cgal_mesh_criteria.cc
@@ -65,6 +65,13 @@ test()
 int
 main()
 {
+  // CGAL uses hand-optimized AVX instructions for certain performance
+  // critical operations that can create (temporary) signalling NaNs and
+  // trigger a spurious floating point exception. Thus disable FE_INVALID:
+#if defined(DEBUG) && defined(DEAL_II_HAVE_FP_EXCEPTIONS)
+  fedisableexcept(FE_INVALID);
+#endif
+
   initlog();
   test();
 }