Perf: optimize function pow in module_gint

source/module_hamilt_lcao/module_gint/gint_tools.h

@@ -136,6 +136,28 @@ class Gint_inout
 
 namespace Gint_Tools
 {
+
+inline double pow(const double base, const int exp)
+{
+    switch (exp)
+    {
+    case 0:
+        return 1.0;
+    case 1:
+        return base;
+    case 2:
+        return base * base;
+    case 3:
+        return base * base * base;
+    case 4:
+        return base * base * base * base;
+    case 5:
+        return base * base * base * base * base;
+    default:
+        double result = std::pow(base, exp);
+        return result;
+    }
+}
 // vindex[pw.bxyz]
 int* get_vindex(const int bxyz,
                 const int bx,

source/module_hamilt_lcao/module_gint/grid_meshball.cpp

@@ -1,4 +1,5 @@
 #include "grid_meshball.h"
+#include "gint_tools.h"  // for pow(double, int)
 #include "module_base/memory.h"
 
 Grid_MeshBall::Grid_MeshBall()
@@ -127,7 +128,7 @@ double Grid_MeshBall::deal_with_atom_spillage(const double *pos)
 					cell[ip] = i*this->bigcell_vec1[ip] +
 						j*this->bigcell_vec2[ip] +
 						k*this->bigcell_vec3[ip];
-					dx += std::pow(cell[ip] - pos[ip], 2);
+					dx += pow(cell[ip] - pos[ip], 2);
 				}
 				r2 = std::min(dx, r2);
 			}

source/module_hamilt_lcao/module_gint/kernels/cuda/interp.cuh

@@ -5,6 +5,28 @@
 
 namespace GintKernel
 {
+static __device__ double pow(double base, int exp)
+{
+    switch (exp)
+    {
+    case 0:
+        return 1.0;
+    case 1:
+        return base;
+    case 2:
+        return base * base;
+    case 3:
+        return base * base * base;
+    case 4:
+        return base * base * base * base;
+    case 5:
+        return base * base * base * base * base;
+    default:
+        double result = std::pow(base, exp);
+        return result;      
+    }
+}
+
 static __device__ void interp_rho(const double dist,
                                   const double delta_r,
                                   const int atype,