47 lines
1.1 KiB
Common Lisp
47 lines
1.1 KiB
Common Lisp
#define G 1.0f
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//6.67384e-11f
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#define epsilon_sq 1.f
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float3 calculate_force(
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float3 first_pos,
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float3 second_pos,
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float first_mass,
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float second_mass)
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{
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float3 d = first_pos - second_pos;
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float q = sqrt(dot(d, d) + epsilon_sq);
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return -G * first_mass * second_mass * d / ( q*q*q );
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}
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kernel void nbody(global const float4* pos_mass_front,
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global float4* pos_mass_back,
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global float4* velocity,
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uint particle_count,
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float dt)
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{
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size_t gid = get_global_id(0);
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float3 my_pos = pos_mass_front[gid].xyz;
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float my_mass = pos_mass_front[gid].w;
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float3 my_vel = velocity[gid].xyz;
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float3 acc = (float3)0.f;
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for (uint i = 0; i < particle_count; i++)
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{
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acc += calculate_force(
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my_pos,
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pos_mass_front[i].xyz,
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my_mass,
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pos_mass_front[i].w
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);
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}
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// updated position and velocity
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my_pos += my_vel * dt + acc * 0.5f * dt * dt;
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my_vel += acc * dt;
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// write to global memory
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pos_mass_back[gid] = (float4)(my_pos, my_mass);
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velocity[gid] = (float4)(my_vel, 0.f);
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}
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