From 6d034596d31b7c9810dfc2cc8f7ffcf0ea1f9e8d Mon Sep 17 00:00:00 2001
From: Evghenii <egaburov@dds.nl>
Date: Sun, 2 Feb 2014 19:01:10 +0100
Subject: [PATCH] +1

---
 examples_ptx/nbody/nbody.cu   | 14 ++++++++++++--
 examples_ptx/nbody/nbody.ispc | 18 ++++++++++++++++--
 2 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/examples_ptx/nbody/nbody.cu b/examples_ptx/nbody/nbody.cu
index cf93f788..4a711882 100644
--- a/examples_ptx/nbody/nbody.cu
+++ b/examples_ptx/nbody/nbody.cu
@@ -39,6 +39,16 @@ void closeNbody()
   closeNbody___export<<<1,1>>>();
 }
 
+static inline __device__
+real rsqrt_real(real r2)
+{
+#if 1
+  return r2> (real)0.0 ? (real)1.0/sqrt(r2) : 0; 
+#else
+  return r2> (real)0.0 ? rsqrt((float)r2) : 0; 
+#endif
+}
+
 
 
 __global__
@@ -75,7 +85,7 @@ void computeForces(
         const real    dy  = jposy - iposy; 
         const real    dz  = jposz - iposz; 
         const real    r2  = dx*dx + dy*dy + dz*dz; 
-        const real  rinv  = r2; // > 0.0 ? rsqrt((float)r2) : 0; 
+        const real  rinv  = rsqrt_real(r2);
         const real mrinv  = -jmass * rinv; 
         const real mrinv3 = mrinv * rinv*rinv; 
         iaccx += mrinv3 * dx; 
@@ -118,7 +128,7 @@ void computeForces(
           const real    dy  = jposy - iposy; 
           const real    dz  = jposz - iposz; 
           const real    r2  = dx*dx + dy*dy + dz*dz; 
-          const real  rinv  = r2 > 0.0 ? 1.0/sqrt(r2) : 0; 
+          const real  rinv  = rsqrt_real(r2);
           const real mrinv  = -jmass * rinv; 
           const real mrinv3 = mrinv * rinv*rinv; 
           iaccx += mrinv3 * dx; 
diff --git a/examples_ptx/nbody/nbody.ispc b/examples_ptx/nbody/nbody.ispc
index 4b98650c..f1d4b22f 100644
--- a/examples_ptx/nbody/nbody.ispc
+++ b/examples_ptx/nbody/nbody.ispc
@@ -26,6 +26,16 @@ void closeNbody()
   delete gpotList;
 }
 
+  static inline
+real rsqrt_real(real r2)
+{
+#if 1
+  return r2> (real)0.0 ? (real)1.0d0/sqrt(r2) : 0; 
+#else
+  return r2> (real)0.0 ? rsqrt((float)r2) : 0; 
+#endif
+}
+
 uniform int nn = programCount;
 
 
@@ -64,7 +74,7 @@ void computeForces(
       const real    dy  = jposy - iposy; 
       const real    dz  = jposz - iposz; 
       const real    r2  = dx*dx + dy*dy + dz*dz; 
-      const real  rinv  = r2> 0.0d ? 1.0/sqrt(r2) : 0; 
+      const real  rinv  = rsqrt_real(r2);
       const real mrinv  = -jmass * rinv; 
       const real mrinv3 = mrinv * rinv*rinv; 
  
@@ -104,7 +114,11 @@ void computeForces(
         const real    dy  = jposy - iposy; 
         const real    dz  = jposz - iposz; 
         const real    r2  = dx*dx + dy*dy + dz*dz; 
-        const real  rinv  = r2 > 0.0d ? 1.0/sqrt(r2) : 0; 
+#if 0 /* faster */
+        const real rinv  = r2> (real)0.0 ? (real)1.0d0/sqrt(r2) : 0; 
+#else
+        const real rinv  = rsqrt_real(r2);
+#endif
         const real mrinv  = -jmass * rinv; 
         const real mrinv3 = mrinv * rinv*rinv;