diff --git a/example.c b/example.c
index 1fd8d0a..e498d68 100644
--- a/example.c
+++ b/example.c
@@ -1,25 +1,25 @@
 #include <stdlib.h>
 
-void etics_external_init(const int n_total);
+void etics_external_init(const int n_total, const double length_scale);
 void etics_external_grav(const double* const A, const int n_act, double x_act[][3], double pot_act[], double a_act[][3]);
 
 int main()
 {
     const int n_total = 1024;
-    etics_external_init(n_total);
+    etics_external_init(n_total, 1.);
 
     srand(19640916);
 
     double x_act[n_total][3], pot_act[n_total], a_act[n_total][3];
     for (int i = 0; i < n_total; i++) {
-        x_act[i][0] = rand();
-        x_act[i][1] = rand();
-        x_act[i][2] = rand();
+        x_act[i][0] = rand()/(double)RAND_MAX;
+        x_act[i][1] = rand()/(double)RAND_MAX;
+        x_act[i][2] = rand()/(double)RAND_MAX;
     }
 
     double A[2048];
     for (int i = 0; i < 2048; i++) {
-        A[i] = rand();
+        A[i] = rand()/(double)RAND_MAX;
     }
 
     etics_external_grav(A, n_total, x_act, pot_act, a_act);
diff --git a/gravity.cpp b/gravity.cpp
index 925c9c9..6c28a75 100644
--- a/gravity.cpp
+++ b/gravity.cpp
@@ -6,10 +6,11 @@ static grapite::Active_particles* particles_i;
 static grapite::Etics_interface* etics_interface;
 
 extern "C"
-void etics_external_init(const int n_total)
+void etics_external_init(const int n_total, const double length_scale)
 {
     particles_i = new grapite::Active_particles{n_total};
     etics_interface = new grapite::Etics_interface{n_total};
+    etics::scf::SetLengthScale(length_scale);
 }
 
 extern "C"
@@ -18,13 +19,17 @@ void etics_external_grav(const double* const A, const int n_act, double x_act[][
     // Load coefficients
     std::span A_complex{reinterpret_cast<const Complex*>(A), 1024};
     std::copy(begin(A_complex), end(A_complex), etics_interface->A_h);
-    etics_interface->GetGpuLock();
-    etics_interface->SendCoeffsToGPU();
-    etics_interface->ReleaseGpuLock();
 
     // Calculate potentials and forces
     particles_i->ni_core  = 0;
     particles_i->ni_total = n_act;
+    for (int i = 0; i < n_act; i++) {
+        grapite::Particle_ext p{};
+        p.m = 1;
+        p.t = 0;
+        p.pos = vec3(x_act[i][0], x_act[i][1], x_act[i][2]);
+        particles_i->add_particle(i, &p);
+    }
     particles_i->flush_memory();
     etics_interface->calculate_gravity(particles_i, grapite::Selector::halo, 0, pot_act, reinterpret_cast<vec3*>(a_act));
 }
\ No newline at end of file