Merge pull request #32 from OpenPIV/copilot/fix-s2n-validation-logic

Fix GPU S2N validation: shape mismatch crash and inverted threshold logic

Author: alexlib

openpiv/gpu/process.py

@@ -1146,7 +1146,7 @@ def _validate_fields(self, u, v, dp_u, dp_v):
         if self.num_validation_iters == 0:
             return u, v, val_locations
         if "s2n" in self.validation_method:
-            s2n_ratio = self._corr_gpu.s2n_ratio
+            s2n_ratio = self._corr_gpu.s2n_ratio.reshape(u.shape)
 
         # Create the validation object.
         self._validation_gpu = Validation(

openpiv/gpu/validation.py

@@ -448,8 +448,10 @@ def _s2n_validation(self, s2n_ratio):
             return
         s2n_tol = log10(self.s2n_tol)
 
-        sig2noise_tol = s2n_ratio / DTYPE_f(s2n_tol)
-        self.val_locations = _local_validation(sig2noise_tol, 1, self.val_locations)
+        # Mark invalid where s2n_ratio < s2n_tol, i.e. (s2n_tol - s2n_ratio) > 0.
+        self.val_locations = _local_validation(
+            DTYPE_f(s2n_tol) - s2n_ratio, 0, self.val_locations
+        )
 
     def _mask_val_locations(self):
         """Removes masked locations from the validation locations."""

openpiv/test/gpu/test_validation.py

@@ -205,7 +205,7 @@ def test_validation_median_num_validation_locations(validation_gpu, peaks_reshap
 def test_validation_s2n_validation(validation_gpu, s2n_ratio):
     tol = log10(validation.S2N_TOL)
 
-    val_locations = validation._local_validation(s2n_ratio / tol, 1).get()
+    val_locations = validation._local_validation(DTYPE_f(tol) - s2n_ratio, 0).get()
     validation_gpu._s2n_validation(s2n_ratio)
     val_locations_gpu = validation_gpu.val_locations.get()