BUG #15438: Handle NaN when computing array range.

A small tweak to the vtkDataArrayPrivate makes it possible for us to
handle NaN in arrays when computing ranges. We should not include NaN
when computing the range. By ensuring that the "left" argument to the
min/max functions is never a NaN, we are assured that they min/max calls
won't return a NaN.

Also added a test for the same.

Common/Core/vtkDataArrayPrivate.txx

@@ -29,16 +29,21 @@ namespace msvc
 // Those min and max functions replace std ones because their
 // implementation used to generate very slow code with MSVC.
 // See https://randomascii.wordpress.com/2013/11/24/stdmin-causing-three-times-slowdown-on-vc/
+// The comparison expression in min/max are written so that if the "condition" is false,
+// the "left" value is returned. This is consistent with STL's implementations
+// and also handles the cases where the right value may be a NaN properly.
+// All code using these methods should ensure that the "left" value is never
+// NaN.
 template <class ValueType>
 ValueType max(const ValueType& left, const ValueType& right)
 {
-  return left > right ? left : right;
+  return right > left ? right : left;
 }
 
 template <class ValueType>
 ValueType min(const ValueType& left, const ValueType& right)
 {
-  return left <= right ? left : right;
+  return right <= left ? right : left;
 }
 }
 #endif
@@ -74,8 +79,8 @@ struct ComputeScalarRange
       {
       for(int i = 0, j = 0; i < NumComps; ++i, j+=2)
         {
-        tempRange[j] = detail::min(value[i], tempRange[j]);
-        tempRange[j+1] = detail::max(value[i], tempRange[j+1]);
+        tempRange[j] = detail::min(tempRange[j], value[i]);
+        tempRange[j+1] = detail::max(tempRange[j+1], value[i]);
         }
       }
 
@@ -164,8 +169,8 @@ bool DoComputeScalarRange(InputIteratorType begin, InputIteratorType end,
       {
       for(int i = 0, j = 0; i < numComp; ++i, j+=2)
         {
-        tempRange[j] = detail::min(value[i], tempRange[j]);
-        tempRange[j+1] = detail::max(value[i], tempRange[j+1]);
+        tempRange[j] = detail::min(tempRange[j], value[i]);
+        tempRange[j+1] = detail::max(tempRange[j+1], value[i]);
         }
       }
 
@@ -210,8 +215,8 @@ bool DoComputeVectorRange(InputIteratorType begin, InputIteratorType end,
       const double t = static_cast<double>(value[i]);
       squaredSum += t * t;
       }
-    range[0] = detail::min(squaredSum, range[0]);
-    range[1] = detail::max(squaredSum, range[1]);
+    range[0] = detail::min(range[0], squaredSum);
+    range[1] = detail::max(range[1], squaredSum);
     }
 
   //now that we have computed the smallest and largest value, take the

IO/Exodus/Testing/Python/CMakeLists.txt

 vtk_add_test_python(
   TestExodusPolyhedra.py
+  TestExodusWithNaN.py,NO_RT,NO_VALID
 )

IO/Exodus/Testing/Python/TestExodusWithNaN.py

+#!/usr/bin/env python
+# This test loads an Exodus file with NaNs and we test that the vtkDataArray
+# returns a correct range for the array with NaNs i.e. not including the NaN.
+from vtk import *
+from vtk.util.misc import vtkGetDataRoot
+VTK_DATA_ROOT = vtkGetDataRoot()
+
+rdr = vtkExodusIIReader()
+rdr.SetFileName(str(VTK_DATA_ROOT) + "/Data/cyl_with_NaN.g")
+rdr.UpdateInformation()
+rdr.SetPointResultArrayStatus("dist_from_origin", 1);
+rdr.Update()
+
+data = rdr.GetOutput().GetBlock(0).GetBlock(0)
+
+# Test that this dataset with NaNs gets a correct range i.e. range without NaNs
+# in it.
+drange = data.GetPointData().GetArray("dist_from_origin").GetRange()[:]
+print "'dist_from_origin' Range: ", drange
+assert (abs(drange[0] - 0.5) < 1e-3) and (abs(drange[1] - 1.118) < 1e-3)

Testing/Data/cyl_with_NaN.g.md5

+df330c4e2d7603b5d7c16d54b1d4d43f