IVGCVSW-3161 Bug Fix in Nearest Neighbor implementation;

             consider 4 neighbors instead of 2.

Signed-off-by: Teresa Charlin <teresa.charlinreyes@arm.com>
Change-Id: Ia724b35f723157e9f51b5345964200f126b98267

1 files changed, 43 insertions, 8 deletions

diff --git a/src/backends/reference/workloads/Resize.cpp b/src/backends/reference/workloads/Resize.cpp
index 0e0bdd7597..3050bae870 100644
--- a/src/backends/reference/workloads/Resize.cpp
+++ b/src/backends/reference/workloads/Resize.cpp
@@ -25,6 +25,11 @@ inline float Lerp(float a, float b, float w)
     return w * b + (1.f - w) * a;
 }
 
+inline double EuclideanDistance(float Xa, float Ya, const unsigned int Xb, const unsigned int Yb)
+{
+    return std::sqrt(pow(Xa - boost::numeric_cast<float>(Xb), 2) + pow(Ya - boost::numeric_cast<float>(Yb), 2));
+}
+
 }// anonymous namespace
 
 void Resize(Decoder<float>&   in,
@@ -104,20 +109,50 @@ void Resize(Decoder<float>&   in,
                             break;
                         }
                         case armnn::ResizeMethod::NearestNeighbor:
-                        default:
                         {
-                            auto distance0 = std::sqrt(pow(fix - boost::numeric_cast<float>(x0), 2) + 
-                                                       pow(fiy - boost::numeric_cast<float>(y0), 2));
-                            auto distance1 = std::sqrt(pow(fix - boost::numeric_cast<float>(x1), 2) +
-                                                       pow(fiy - boost::numeric_cast<float>(y1), 2));
-
-                            unsigned int xNearest = distance0 <= distance1? x0 : x1;
-                            unsigned int yNearest = distance0 <= distance1? y0 : y1;
+                            // calculate euclidean distance to the 4 neighbours
+                            auto distance00 = EuclideanDistance(fix, fiy, x0, y0);
+                            auto distance01 = EuclideanDistance(fix, fiy, x0, y1);
+                            auto distance10 = EuclideanDistance(fix, fiy, x1, y0);
+                            auto distance11 = EuclideanDistance(fix, fiy, x1, y1);
+
+                            auto minimum = std::min( { distance00, distance01, distance10, distance11 } );
+
+                            unsigned int xNearest = 0;
+                            unsigned int yNearest = 0;
+
+                            if (minimum == distance00)
+                            {
+                               xNearest = x0;
+                               yNearest = y0;
+                            }
+                            else if (minimum == distance01)
+                            {
+                                xNearest = x0;
+                                yNearest = y1;
+                            }
+                            else if (minimum == distance10)
+                            {
+                                xNearest = x1;
+                                yNearest = y0;
+                            }
+                            else if (minimum == distance11)
+                            {
+                                xNearest = x1;
+                                yNearest = y1;
+                            }
+                            else
+                            {
+                                throw armnn::InvalidArgumentException("Resize Nearest Neighbor failure");
+                            }
 
                             in[dataLayout.GetIndex(inputShape, n, c, yNearest, xNearest)];
                             interpolatedValue = in.Get();
                             break;
                         }
+                        default:
+                            throw armnn::InvalidArgumentException("Unknown resize method: " +
+                                                                  std::to_string(static_cast<int>(resizeMethod)));
                     }
                     out[dataLayout.GetIndex(outputShape, n, c, y, x)];
                     out.Set(interpolatedValue);