Add force calculation kernel and fix incorrect ctest configuration for Cuda tests

kernels/CMakeLists.txt

@@ -2,12 +2,14 @@ project(${NAME}_cuda_lib CUDA CXX)
 
 set(HEADER_FILES
     pair_potentials.cuh
+    forces.cuh
 )
 set(SOURCE_FILES
+    forces.cu
 )
 
 # The library contains header and source files.
-add_library(${NAME}_cuda_lib INTERFACE
+add_library(${NAME}_cuda_lib STATIC
     ${SOURCE_FILES}
     ${HEADER_FILES}
 )

kernels/forces.cu

@@ -0,0 +1,36 @@
+#include "forces.cuh"
+
+__global__ void CAC::calc_forces_and_energies(real *xs, real *forces,
+                                              real *energies, int n_particles,
+                                              real *box_len,
+                                              PairPotential &potential) {
+  int i = blockIdx.x * blockDim.x + threadIdx.x;
+  if (i < n_particles) {
+    real xi = xs[3 * i];
+    real yi = xs[3 * i + 1];
+    real zi = xs[3 * i + 2];
+
+    for (int j = 0; j < n_particles; j++) {
+      if (i != j) {
+        real xj = xs[3 * j];
+        real yj = xs[3 * j + 1];
+        real zj = xs[3 * j + 2];
+
+        real dx = xi - xj;
+        real dy = yi - yj;
+        real dz = zi - zj;
+
+        // Apply periodic boundary conditions
+        dx -= box_len[0] * round(dx / box_len[0]);
+        dy -= box_len[1] * round(dy / box_len[1]);
+        dz -= box_len[2] * round(dz / box_len[2]);
+
+        ForceAndEnergy sol = potential.calc_force_and_energy({dx, dy, dz});
+        forces[3 * i] += sol.force.x;
+        forces[3 * i + 1] += sol.force.y;
+        forces[3 * i + 2] += sol.force.z;
+        energies[i] = sol.energy;
+      }
+    }
+  }
+}

kernels/forces.cuh

@@ -0,0 +1,19 @@
+#ifndef FORCES_CUH
+#define FORCES_CUH
+
+#include "pair_potentials.cuh"
+#include "precision.hpp"
+namespace CAC {
+/**
+ * Calculate forces and energies using CUDA for acceleration
+ * This code currently only accepts a single PairPotential object and does an
+ * n^2 force calculation. Future improvements will:
+ *   - Allow for neighbor listing
+ *   - Allow for overlaid force calculations
+ */
+__global__ void calc_forces_and_energies(real *xs, real *forces, real *energies,
+                                         int n_particles, real *box_bd,
+                                         PairPotential &potential);
+} // namespace CAC
+
+#endif

kernels/pair_potentials.cuh

@@ -1,5 +1,5 @@
-#ifndef POTENTIALS_H
-#define POTENTIALS_H
+#ifndef POTENTIALS_CUH
+#define POTENTIALS_CUH
 
 #include "precision.hpp"
 #include "vec3.h"
@@ -84,8 +84,8 @@ struct LennardJones : PairPotential {
     }
   };
 
-  CUDA_CALLABLE ~LennardJones(){};
+  CUDA_CALLABLE inline ~LennardJones(){};
 };
 
-PairPotential::~PairPotential() {};
+inline PairPotential::~PairPotential() {};
 #endif