Change NMS threshold criteria in GPU implementation to match CPU's (which was recently updated to fix regression). Also add a test for validating iou_threshold set to 0.0.

PiperOrigin-RevId: 342012687
Change-Id: I9614724ab371ec3083a3d8506d2a4437d25cbd90

Author: hyeygit

tensorflow/core/kernels/image/non_max_suppression_op.cu.cc

@@ -89,7 +89,7 @@ __device__ EIGEN_STRONG_INLINE bool OverThreshold(const Box* a, const Box* b,
   const float aa = intersection;
   const float bb = a_area + b_area - intersection;
   const float bt = bb * iou_threshold;
-  return aa >= bt;
+  return aa > bt;
 }
 
 template <bool flip_box>

tensorflow/python/ops/image_ops_test.py

@@ -4944,6 +4944,21 @@ def testDataTypes(self):
         selected_indices = self.evaluate(selected_indices)
         self.assertAllClose(selected_indices, [3, 0, 5])
 
+  def testZeroIOUThreshold(self):
+    boxes_np = [[0, 0, 1, 1], [0, 0.1, 1, 1.1], [0, -0.1, 1, 0.9],
+                [0, 10, 1, 11], [0, 10.1, 1, 11.1], [0, 100, 1, 101]]
+    scores_np = [1., 1., 1., 1., 1., 1.]
+    max_output_size_np = 3
+    iou_threshold_np = 0.0
+    with self.cached_session():
+      boxes = constant_op.constant(boxes_np)
+      scores = constant_op.constant(scores_np)
+      max_output_size = constant_op.constant(max_output_size_np)
+      iou_threshold = constant_op.constant(iou_threshold_np)
+      selected_indices = image_ops.non_max_suppression(
+          boxes, scores, max_output_size, iou_threshold)
+      self.assertAllClose(selected_indices, [0, 3, 5])
+
 
 class NonMaxSuppressionWithScoresTest(test_util.TensorFlowTestCase):