Fix bug in SSE implementations

include/kernel.txx

@@ -1750,7 +1750,7 @@ void stokes_grad(T* r_src, int src_cnt, T* v_src_, int dof, T* r_trg, int trg_cn
 }
 
 #ifndef __MIC__
-#ifdef USE_SSE
+#if defined __SSE3__
 namespace
 {
 #define IDEAL_ALIGNMENT 16
@@ -1865,7 +1865,7 @@ namespace
         double y = ty[i] - sy[j];
         double z = tz[i] - sz[j];
         double r2 = x*x + y*y + z*z;
-        double r = pvfmm::sqrt<T>(r2);
+        double r = pvfmm::sqrt<double>(r2);
         double invdr;
         if (r == 0)
           invdr = 0;
@@ -2040,7 +2040,7 @@ namespace
         double y = ty[i] - sy[j];
         double z = tz[i] - sz[j];
         double r2 = x*x + y*y + z*z;
-        double r = pvfmm::sqrt<T>(r2);
+        double r = pvfmm::sqrt<double>(r2);
         double invdr;
         if (r == 0)
           invdr = 0;
@@ -2229,7 +2229,7 @@ namespace
         double y = ty[i] - sy[j];
         double z = tz[i] - sz[j];
         double r2 = x*x + y*y + z*z;
-        double r = pvfmm::sqrt<T>(r2);
+        double r = pvfmm::sqrt<double>(r2);
         double invdr;
         if (r == 0)
           invdr = 0;