Merge "Merge branch release-4-6 into release-5-0" into release-5-0

diff --git a/src/gromacs/legacyheaders/types/simple.h b/src/gromacs/legacyheaders/types/simple.h
index bf1a5216af6ce355a904433518145c5e11c3f27d..de1ebdcb77865105721847e8926eb4158ac4eef7 100644 (file)
--- a/src/gromacs/legacyheaders/types/simple.h
+++ b/src/gromacs/legacyheaders/types/simple.h
@@ -109,6 +109,25 @@ typedef int         atom_id;      /* To indicate an atoms id         */
 /*! \brief Minimum single precision value */
 #define GMX_FLOAT_MIN    1.175494351E-38F
 
+#ifdef __PGI
+/* The portland group x86 C/C++ compilers do not treat negative zero initializers
+ * correctly, but "optimizes" them to positive zero, so we implement it explicitly.
+ * These constructs are optimized to simple loads at compile time. If you want to
+ * use them on other compilers those have to support gcc preprocessor extensions.
+ * Note: These initializers might be sensitive to the endianness (which can
+ * be different for byte and word order), so check that it works for your platform
+ * and add a separate section if necessary before adding to the ifdef above.
+ */
+#    define GMX_DOUBLE_NEGZERO  ({ const union { int  di[2]; double d; } _gmx_dzero = {0, -2147483648}; _gmx_dzero.d; })
+#    define GMX_FLOAT_NEGZERO   ({ const union { int  fi; float f; } _gmx_fzero = {-2147483648}; _gmx_fzero.f; })
+#else
+/*! \brief Negative zero in double */
+#    define GMX_DOUBLE_NEGZERO  (-0.0)
+
+/*! \brief Negative zero in float */
+#    define GMX_FLOAT_NEGZERO   (-0.0f)
+#endif
+
 
 /* Check whether we already have a real type! */
 #ifdef GMX_DOUBLE
@@ -118,10 +137,11 @@ typedef double      real;
 #define HAVE_REAL
 #endif
 
-#define GMX_MPI_REAL    MPI_DOUBLE
-#define GMX_REAL_EPS    GMX_DOUBLE_EPS
-#define GMX_REAL_MIN    GMX_DOUBLE_MIN
-#define GMX_REAL_MAX    GMX_DOUBLE_MAX
+#define GMX_MPI_REAL      MPI_DOUBLE
+#define GMX_REAL_EPS      GMX_DOUBLE_EPS
+#define GMX_REAL_MIN      GMX_DOUBLE_MIN
+#define GMX_REAL_MAX      GMX_DOUBLE_MAX
+#define GMX_REAL_NEGZERO  GMX_DOUBLE_NEGZERO
 #define gmx_real_fullprecision_pfmt "%21.14e"
 #else
 
@@ -130,10 +150,11 @@ typedef float           real;
 #define HAVE_REAL
 #endif
 
-#define GMX_MPI_REAL    MPI_FLOAT
-#define GMX_REAL_EPS    GMX_FLOAT_EPS
-#define GMX_REAL_MIN    GMX_FLOAT_MIN
-#define GMX_REAL_MAX    GMX_FLOAT_MAX
+#define GMX_MPI_REAL      MPI_FLOAT
+#define GMX_REAL_EPS      GMX_FLOAT_EPS
+#define GMX_REAL_MIN      GMX_FLOAT_MIN
+#define GMX_REAL_MAX      GMX_FLOAT_MAX
+#define GMX_REAL_NEGZERO  GMX_FLOAT_NEGZERO
 #define gmx_real_fullprecision_pfmt "%14.7e"
 #endif
 

diff --git a/src/gromacs/simd/impl_intel_mic/impl_intel_mic.h b/src/gromacs/simd/impl_intel_mic/impl_intel_mic.h
index 8c62c3a43b8e070a9d81f68376ce218a1ee52f44..e3d49126f0ebf5132ad8744c2e2caa198f591f18 100644 (file)
--- a/src/gromacs/simd/impl_intel_mic/impl_intel_mic.h
+++ b/src/gromacs/simd/impl_intel_mic/impl_intel_mic.h
@@ -98,7 +98,7 @@
 #define gmx_simd_xor_f(a, b)        _mm512_castsi512_ps(_mm512_xor_epi32(_mm512_castps_si512(a), _mm512_castps_si512(b)))
 #define gmx_simd_rsqrt_f           _mm512_rsqrt23_ps
 #define gmx_simd_rcp_f             _mm512_rcp23_ps
-#define gmx_simd_fabs_f(x)         gmx_simd_andnot_f(_mm512_set1_ps(-0.0), x)
+#define gmx_simd_fabs_f(x)         gmx_simd_andnot_f(_mm512_set1_ps(GMX_FLOAT_NEGZERO), x)
 #define gmx_simd_fneg_f(x)         _mm512_addn_ps(x, _mm512_setzero_ps())
 #define gmx_simd_max_f             _mm512_gmax_ps
 #define gmx_simd_min_f             _mm512_gmin_ps
@@ -189,7 +189,7 @@
 #define gmx_simd_xor_d(a, b)       _mm512_castsi512_pd(_mm512_xor_epi32(_mm512_castpd_si512(a), _mm512_castpd_si512(b)))
 #define gmx_simd_rsqrt_d(x)        _mm512_cvtpslo_pd(_mm512_rsqrt23_ps(_mm512_cvtpd_pslo(x)))
 #define gmx_simd_rcp_d(x)          _mm512_cvtpslo_pd(_mm512_rcp23_ps(_mm512_cvtpd_pslo(x)))
-#define gmx_simd_fabs_d(x)         gmx_simd_andnot_d(_mm512_set1_pd(-0.0), x)
+#define gmx_simd_fabs_d(x)         gmx_simd_andnot_d(_mm512_set1_pd(GMX_DOUBLE_NEGZERO), x)
 #define gmx_simd_fneg_d(x)         _mm512_addn_pd(x, _mm512_setzero_pd())
 #define gmx_simd_max_d             _mm512_gmax_pd
 #define gmx_simd_min_d             _mm512_gmin_pd
@@ -282,7 +282,7 @@
 #define gmx_simd4_or_f(a, b)        _mm512_castsi512_ps(_mm512_mask_or_epi32(_mm512_undefined_epi32(), gmx_simd4_mask, _mm512_castps_si512(a), _mm512_castps_si512(b)))
 #define gmx_simd4_xor_f(a, b)       _mm512_castsi512_ps(_mm512_mask_xor_epi32(_mm512_undefined_epi32(), gmx_simd4_mask, _mm512_castps_si512(a), _mm512_castps_si512(b)))
 #define gmx_simd4_rsqrt_f(a)        _mm512_mask_rsqrt23_ps(_mm512_undefined_ps(), gmx_simd4_mask, a)
-#define gmx_simd4_fabs_f(x)         gmx_simd4_andnot_f(_mm512_set1_ps(-0.0), x)
+#define gmx_simd4_fabs_f(x)         gmx_simd4_andnot_f(_mm512_set1_ps(GMX_FLOAT_NEGZERO), x)
 #define gmx_simd4_fneg_f(x)         _mm512_mask_addn_ps(_mm512_undefined_ps(), gmx_simd4_mask, x, _mm512_setzero_ps())
 #define gmx_simd4_max_f(a, b)       _mm512_mask_gmax_ps(_mm512_undefined_ps(), gmx_simd4_mask, a, b)
 #define gmx_simd4_min_f(a, b)       _mm512_mask_gmin_ps(_mm512_undefined_ps(), gmx_simd4_mask, a, b)
@@ -325,7 +325,7 @@
 #define gmx_simd4_or_d(a, b)        _mm512_castsi512_pd(_mm512_mask_or_epi32(_mm512_undefined_epi32(), mask_loh, _mm512_castpd_si512(a), _mm512_castpd_si512(b)))
 #define gmx_simd4_xor_d(a, b)       _mm512_castsi512_pd(_mm512_mask_xor_epi32(_mm512_undefined_epi32(), mask_loh, _mm512_castpd_si512(a), _mm512_castpd_si512(b)))
 #define gmx_simd4_rsqrt_d(a)        _mm512_mask_cvtpslo_pd(_mm512_undefined_pd(), gmx_simd4_mask, _mm512_mask_rsqrt23_ps(_mm512_undefined_ps(), gmx_simd4_mask, _mm512_mask_cvtpd_pslo(_mm512_undefined_ps(), gmx_simd4_mask, x)))
-#define gmx_simd4_fabs_d(x)         gmx_simd4_andnot_d(_mm512_set1_pd(-0.0), x)
+#define gmx_simd4_fabs_d(x)         gmx_simd4_andnot_d(_mm512_set1_pd(GMX_DOUBLE_NEGZERO), x)
 #define gmx_simd4_fneg_d(x)         _mm512_mask_addn_pd(_mm512_undefined_pd(), gmx_simd4_mask, x, _mm512_setzero_pd())
 #define gmx_simd4_max_d(a, b)       _mm512_mask_gmax_pd(_mm512_undefined_pd(), gmx_simd4_mask, a, b)
 #define gmx_simd4_min_d(a, b)       _mm512_mask_gmin_pd(_mm512_undefined_pd(), gmx_simd4_mask, a, b)

diff --git a/src/gromacs/simd/impl_x86_avx_128_fma/impl_x86_avx_128_fma.h b/src/gromacs/simd/impl_x86_avx_128_fma/impl_x86_avx_128_fma.h
index 823bfe81b996ef2aaefbfce38b1791c5b8ed6785..5b3096bee322f5fe367c39da2165a030ea6b1db7 100644 (file)
--- a/src/gromacs/simd/impl_x86_avx_128_fma/impl_x86_avx_128_fma.h
+++ b/src/gromacs/simd/impl_x86_avx_128_fma/impl_x86_avx_128_fma.h
@@ -104,8 +104,8 @@
 #define gmx_simd4_or_d                   _mm256_or_pd
 #define gmx_simd4_xor_d                  _mm256_xor_pd
 #define gmx_simd4_rsqrt_d(x)             _mm256_cvtps_pd(_mm_rsqrt_ps(_mm256_cvtpd_ps(x)))
-#define gmx_simd4_fabs_d(x)              _mm256_andnot_pd(_mm256_set1_pd(-0.0), x)
-#define gmx_simd4_fneg_d(x)              _mm256_xor_pd(x, _mm256_set1_pd(-0.0))
+#define gmx_simd4_fabs_d(x)              _mm256_andnot_pd(_mm256_set1_pd(GMX_DOUBLE_NEGZERO), x)
+#define gmx_simd4_fneg_d(x)              _mm256_xor_pd(x, _mm256_set1_pd(GMX_DOUBLE_NEGZERO))
 #define gmx_simd4_max_d                  _mm256_max_pd
 #define gmx_simd4_min_d                  _mm256_min_pd
 #define gmx_simd4_round_d(x)             _mm256_round_pd(x, _MM_FROUND_NINT)

diff --git a/src/gromacs/simd/impl_x86_avx_256/impl_x86_avx_256.h b/src/gromacs/simd/impl_x86_avx_256/impl_x86_avx_256.h
index d787708b4c0f6e44cd68ed55b727f8190774a02b..cff1a7e2cbd00bb782aadfba2b862214706a98d1 100644 (file)
--- a/src/gromacs/simd/impl_x86_avx_256/impl_x86_avx_256.h
+++ b/src/gromacs/simd/impl_x86_avx_256/impl_x86_avx_256.h
@@ -105,8 +105,8 @@
 #define gmx_simd_xor_f             _mm256_xor_ps
 #define gmx_simd_rsqrt_f           _mm256_rsqrt_ps
 #define gmx_simd_rcp_f             _mm256_rcp_ps
-#define gmx_simd_fabs_f(x)         _mm256_andnot_ps(_mm256_set1_ps(-0.0), x)
-#define gmx_simd_fneg_f(x)         _mm256_xor_ps(x, _mm256_set1_ps(-0.0))
+#define gmx_simd_fabs_f(x)         _mm256_andnot_ps(_mm256_set1_ps(GMX_FLOAT_NEGZERO), x)
+#define gmx_simd_fneg_f(x)         _mm256_xor_ps(x, _mm256_set1_ps(GMX_FLOAT_NEGZERO))
 #define gmx_simd_max_f             _mm256_max_ps
 #define gmx_simd_min_f             _mm256_min_ps
 #define gmx_simd_round_f(x)        _mm256_round_ps(x, _MM_FROUND_NINT)

diff --git a/src/gromacs/simd/impl_x86_sse2/impl_x86_sse2.h b/src/gromacs/simd/impl_x86_sse2/impl_x86_sse2.h
index 5d6b195965b25441f3bc1ca030dbfe6d51dd4b98..7aab27ae21c5faad2de33dde08b39594b00498e8 100644 (file)
--- a/src/gromacs/simd/impl_x86_sse2/impl_x86_sse2.h
+++ b/src/gromacs/simd/impl_x86_sse2/impl_x86_sse2.h
@@ -99,8 +99,8 @@
 #define gmx_simd_xor_f            _mm_xor_ps
 #define gmx_simd_rsqrt_f          _mm_rsqrt_ps
 #define gmx_simd_rcp_f            _mm_rcp_ps
-#define gmx_simd_fabs_f(x)        _mm_andnot_ps(_mm_set1_ps(-0.0), x)
-#define gmx_simd_fneg_f(x)        _mm_xor_ps(x, _mm_set1_ps(-0.0))
+#define gmx_simd_fabs_f(x)        _mm_andnot_ps(_mm_set1_ps(GMX_FLOAT_NEGZERO), x)
+#define gmx_simd_fneg_f(x)        _mm_xor_ps(x, _mm_set1_ps(GMX_FLOAT_NEGZERO))
 #define gmx_simd_max_f            _mm_max_ps
 #define gmx_simd_min_f            _mm_min_ps
 #define gmx_simd_round_f(x)       _mm_cvtepi32_ps(_mm_cvtps_epi32(x))
@@ -183,8 +183,8 @@
 #define gmx_simd_rsqrt_d(x)        _mm_cvtps_pd(_mm_rsqrt_ps(_mm_cvtpd_ps(x)))
 /* Don't use FMA for sqrt N-R iterations - this saves 1 instruction without FMA hardware */
 #define gmx_simd_rcp_d(x)          _mm_cvtps_pd(_mm_rcp_ps(_mm_cvtpd_ps(x)))
-#define gmx_simd_fabs_d(x)         _mm_andnot_pd(_mm_set1_pd(-0.0), x)
-#define gmx_simd_fneg_d(x)         _mm_xor_pd(x, _mm_set1_pd(-0.0))
+#define gmx_simd_fabs_d(x)         _mm_andnot_pd(_mm_set1_pd(GMX_DOUBLE_NEGZERO), x)
+#define gmx_simd_fneg_d(x)         _mm_xor_pd(x, _mm_set1_pd(GMX_DOUBLE_NEGZERO))
 #define gmx_simd_max_d             _mm_max_pd
 #define gmx_simd_min_d             _mm_min_pd
 #define gmx_simd_round_d(x)        _mm_cvtepi32_pd(_mm_cvtpd_epi32(x))

diff --git a/src/gromacs/simd/simd_math.h b/src/gromacs/simd/simd_math.h
index 1f6dc08361ade3a6ee3c77a1cba1c839b10c9a2a..68ab6774ef0031b3f4b71ca5cceb21663245c59f 100644 (file)
--- a/src/gromacs/simd/simd_math.h
+++ b/src/gromacs/simd/simd_math.h
@@ -124,7 +124,7 @@ static gmx_inline gmx_simd_float_t gmx_simdcall
 gmx_simd_xor_sign_f(gmx_simd_float_t a, gmx_simd_float_t b)
 {
 #ifdef GMX_SIMD_HAVE_LOGICAL
-    return gmx_simd_xor_f(a, gmx_simd_and_f(gmx_simd_set1_f(-0.0), b));
+    return gmx_simd_xor_f(a, gmx_simd_and_f(gmx_simd_set1_f(GMX_FLOAT_NEGZERO), b));
 #else
     return gmx_simd_blendv_f(a, gmx_simd_fneg_f(a), gmx_simd_cmplt_f(b, gmx_simd_setzero_f()));
 #endif
@@ -729,8 +729,8 @@ gmx_simd_sincos_f(gmx_simd_float_t x, gmx_simd_float_t *sinval, gmx_simd_float_t
     y       = gmx_simd_round_f(z);
 
     mask    = gmx_simd_cvt_fib2fb(gmx_simd_cmpeq_fi(gmx_simd_and_fi(iy, ione), gmx_simd_setzero_fi()));
-    ssign   = gmx_simd_blendzero_f(gmx_simd_set1_f(-0.0f), gmx_simd_cvt_fib2fb(gmx_simd_cmpeq_fi(gmx_simd_and_fi(iy, itwo), itwo)));
-    csign   = gmx_simd_blendzero_f(gmx_simd_set1_f(-0.0f), gmx_simd_cvt_fib2fb(gmx_simd_cmpeq_fi(gmx_simd_and_fi(gmx_simd_add_fi(iy, ione), itwo), itwo)));
+    ssign   = gmx_simd_blendzero_f(gmx_simd_set1_f(GMX_FLOAT_NEGZERO), gmx_simd_cvt_fib2fb(gmx_simd_cmpeq_fi(gmx_simd_and_fi(iy, itwo), itwo)));
+    csign   = gmx_simd_blendzero_f(gmx_simd_set1_f(GMX_FLOAT_NEGZERO), gmx_simd_cvt_fib2fb(gmx_simd_cmpeq_fi(gmx_simd_and_fi(gmx_simd_add_fi(iy, ione), itwo), itwo)));
 #else
     const gmx_simd_float_t  quarter         = gmx_simd_set1_f(0.25f);
     const gmx_simd_float_t  minusquarter    = gmx_simd_set1_f(-0.25f);
@@ -766,8 +766,8 @@ gmx_simd_sincos_f(gmx_simd_float_t x, gmx_simd_float_t *sinval, gmx_simd_float_t
      * active or inactive - you will get errors if only one is used.
      */
 #    ifdef GMX_SIMD_HAVE_LOGICAL
-    ssign   = gmx_simd_and_f(ssign, gmx_simd_set1_f(-0.0f));
-    csign   = gmx_simd_andnot_f(q, gmx_simd_set1_f(-0.0f));
+    ssign   = gmx_simd_and_f(ssign, gmx_simd_set1_f(GMX_FLOAT_NEGZERO));
+    csign   = gmx_simd_andnot_f(q, gmx_simd_set1_f(GMX_FLOAT_NEGZERO));
     ssign   = gmx_simd_xor_f(ssign, csign);
 #    else
     csign   = gmx_simd_xor_sign_f(gmx_simd_set1_f(-1.0f), q);
@@ -884,7 +884,7 @@ gmx_simd_tan_f(gmx_simd_float_t x)
     x       = gmx_simd_fnmadd_f(y, argred1, x);
     x       = gmx_simd_fnmadd_f(y, argred2, x);
     x       = gmx_simd_fnmadd_f(y, argred3, x);
-    x       = gmx_simd_xor_f(gmx_simd_blendzero_f(gmx_simd_set1_f(-0.0f), mask), x);
+    x       = gmx_simd_xor_f(gmx_simd_blendzero_f(gmx_simd_set1_f(GMX_FLOAT_NEGZERO), mask), x);
 #else
     const gmx_simd_float_t  quarter         = gmx_simd_set1_f(0.25f);
     const gmx_simd_float_t  half            = gmx_simd_set1_f(0.5f);
@@ -1338,7 +1338,7 @@ static gmx_inline gmx_simd_double_t gmx_simdcall
 gmx_simd_xor_sign_d(gmx_simd_double_t a, gmx_simd_double_t b)
 {
 #ifdef GMX_SIMD_HAVE_LOGICAL
-    return gmx_simd_xor_d(a, gmx_simd_and_d(gmx_simd_set1_d(-0.0), b));
+    return gmx_simd_xor_d(a, gmx_simd_and_d(gmx_simd_set1_d(GMX_DOUBLE_NEGZERO), b));
 #else
     return gmx_simd_blendv_d(a, gmx_simd_fneg_d(a), gmx_simd_cmplt_d(b, gmx_simd_setzero_d()));
 #endif
@@ -2025,8 +2025,8 @@ gmx_simd_sincos_d(gmx_simd_double_t x, gmx_simd_double_t *sinval, gmx_simd_doubl
     y       = gmx_simd_round_d(z);
 
     mask    = gmx_simd_cvt_dib2db(gmx_simd_cmpeq_di(gmx_simd_and_di(iy, ione), gmx_simd_setzero_di()));
-    ssign   = gmx_simd_blendzero_d(gmx_simd_set1_d(-0.0), gmx_simd_cvt_dib2db(gmx_simd_cmpeq_di(gmx_simd_and_di(iy, itwo), itwo)));
-    csign   = gmx_simd_blendzero_d(gmx_simd_set1_d(-0.0), gmx_simd_cvt_dib2db(gmx_simd_cmpeq_di(gmx_simd_and_di(gmx_simd_add_di(iy, ione), itwo), itwo)));
+    ssign   = gmx_simd_blendzero_d(gmx_simd_set1_d(GMX_DOUBLE_NEGZERO), gmx_simd_cvt_dib2db(gmx_simd_cmpeq_di(gmx_simd_and_di(iy, itwo), itwo)));
+    csign   = gmx_simd_blendzero_d(gmx_simd_set1_d(GMX_DOUBLE_NEGZERO), gmx_simd_cvt_dib2db(gmx_simd_cmpeq_di(gmx_simd_and_di(gmx_simd_add_di(iy, ione), itwo), itwo)));
 #else
     const gmx_simd_double_t  quarter         = gmx_simd_set1_d(0.25);
     const gmx_simd_double_t  minusquarter    = gmx_simd_set1_d(-0.25);
@@ -2062,8 +2062,8 @@ gmx_simd_sincos_d(gmx_simd_double_t x, gmx_simd_double_t *sinval, gmx_simd_doubl
      * active or inactive - you will get errors if only one is used.
      */
 #    ifdef GMX_SIMD_HAVE_LOGICAL
-    ssign   = gmx_simd_and_d(ssign, gmx_simd_set1_d(-0.0));
-    csign   = gmx_simd_andnot_d(q, gmx_simd_set1_d(-0.0));
+    ssign   = gmx_simd_and_d(ssign, gmx_simd_set1_d(GMX_DOUBLE_NEGZERO));
+    csign   = gmx_simd_andnot_d(q, gmx_simd_set1_d(GMX_DOUBLE_NEGZERO));
     ssign   = gmx_simd_xor_d(ssign, csign);
 #    else
     csign   = gmx_simd_xor_sign_d(gmx_simd_set1_d(-1.0), q);
@@ -2179,7 +2179,7 @@ gmx_simd_tan_d(gmx_simd_double_t x)
     x       = gmx_simd_fnmadd_d(y, argred1, x);
     x       = gmx_simd_fnmadd_d(y, argred2, x);
     x       = gmx_simd_fnmadd_d(y, argred3, x);
-    x       = gmx_simd_xor_d(gmx_simd_blendzero_d(gmx_simd_set1_d(-0.0), mask), x);
+    x       = gmx_simd_xor_d(gmx_simd_blendzero_d(gmx_simd_set1_d(GMX_DOUBLE_NEGZERO), mask), x);
 #else
     const gmx_simd_double_t  quarter         = gmx_simd_set1_d(0.25);
     const gmx_simd_double_t  half            = gmx_simd_set1_d(0.5);

diff --git a/src/testutils/tests/testasserts_tests.cpp b/src/testutils/tests/testasserts_tests.cpp
index 111bbc5e627bf0d2ee0aaf3fc7996fb155c1b317..c586374863360c74c40cde97fa39f94e6f6b9f7a 100644 (file)
--- a/src/testutils/tests/testasserts_tests.cpp
+++ b/src/testutils/tests/testasserts_tests.cpp
@@ -75,7 +75,7 @@ TEST(FloatingPointDifferenceTest, HandlesEqualValues)
 
 TEST(FloatingPointDifferenceTest, HandlesZerosOfDifferentSign)
 {
-    FloatingPointDifference diff(0.0, -0.0);
+    FloatingPointDifference diff(0.0, GMX_DOUBLE_NEGZERO);
     EXPECT_FALSE(diff.isNaN());
     EXPECT_EQ(0.0, diff.asAbsolute());
     EXPECT_EQ(0U,  diff.asUlps());
@@ -91,7 +91,7 @@ TEST(FloatingPointDifferenceTest, HandlesSignComparisonWithZero)
         EXPECT_TRUE(diff.signsDiffer());
     }
     {
-        FloatingPointDifference diff(-0.0, -1.2);
+        FloatingPointDifference diff(GMX_DOUBLE_NEGZERO, -1.2);
         EXPECT_FALSE(diff.isNaN());
         EXPECT_DOUBLE_EQ(1.2, diff.asAbsolute());
         EXPECT_FALSE(diff.signsDiffer());
@@ -120,7 +120,7 @@ TEST(FloatingPointDifferenceTest, HandlesUlpDifferences)
 
 TEST(FloatingPointDifferenceTest, HandlesUlpDifferenceAcrossZero)
 {
-    const double            first  = addUlps(-0.0, 2);
+    const double            first  = addUlps(GMX_DOUBLE_NEGZERO, 2);
     const double            second = addUlps( 0.0, 2);
     FloatingPointDifference diff(first, second);
     EXPECT_FALSE(diff.isNaN());