Swish.metal

#include <metal_stdlib>
using namespace metal;

kernel void swish(
  texture2d_array<half, access::read> inTexture [[texture(0)]],
  texture2d_array<half, access::write> outTexture [[texture(1)]],
  ushort3 gid [[thread_position_in_grid]])
{
  if (gid.x >= outTexture.get_width() || gid.y >= outTexture.get_height()) {
    return;
  }

  const float4 x = float4(inTexture.read(gid.xy, gid.z));
  const float4 y = x / (1.0f + exp(-x));
  outTexture.write(half4(y), gid.xy, gid.z);
}