clean up index helpers and repo-level md files

CHANGELOG → CHANGELOG.md

@@ -26,6 +26,15 @@ Everything below is merged to `main` but not yet tagged/released.
   every dimensionality and included in the corresponding `Strategy*Enum` types.
 
 ### Changed
+- **Breaking:** `find_nearest_index` is renamed to `locate_lower_index` and, along with
+  the other grid/index search helpers (`step_index` -> `locate_step_index`,
+  `uniform_lower_index` -> `locate_lower_index_uniform`, `exact_index`,
+  `check_uniform_grid`), moves from `strategy::traits` to a new `strategy::utils`
+  module — `traits` now holds only the `Strategy1D`/`2D`/`3D`/`ND` trait definitions.
+  No deprecation shim, matching the other breaking renames in this release.
+  `locate_lower_index` also now clamps out-of-range points to `[0, len - 2]` itself,
+  rather than relying on each `Linear` call site to inline the same clamp before
+  calling it.
 - **Breaking:** `LeftNearest` and `RightNearest` are removed. Migrate to
   `Step::from(StepDirection::Lower)` / `Step::from(StepDirection::Upper)`, or the
   leaner `StepLower` / `StepUpper` markers.

LICENSE → LICENSE.md

@@ -1,6 +1,6 @@
 BSD 3-Clause License
 
-Copyright (c) 2024, Alliance for Sustainable Energy, LLC
+Copyright (c) 2024, Alliance for Energy Innovation, LLC
 
 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions are met:

src/interpolator/n/strategies.rs

@@ -27,15 +27,7 @@ where
             if grid[dim].is_empty() {
                 continue;
             }
-            // Binary search for an exact match: find_nearest_index returns the lower bracket,
-            // so the point can only be exactly equal to grid[lower] or grid[lower+1].
-            let lower = if &point[dim] < grid[dim].first().unwrap() {
-                0
-            } else if &point[dim] > grid[dim].last().unwrap() {
-                grid[dim].len() - 2
-            } else {
-                find_nearest_index(grid[dim].view(), &point[dim])
-            };
+            let lower = locate_lower_index(grid[dim].view(), &point[dim]);
             let pos = exact_index(grid[dim].view(), lower, &point[dim]);
             if let Some(pos) = pos {
                 point.remove(dim);
@@ -57,13 +49,7 @@ where
         for dim in 0..n {
             // Extrapolation is checked previously in Interpolator::interpolate,
             // meaning by now, point is within grid bounds or extrapolation is enabled
-            let lower_idx = if &point[dim] < grid[dim].first().unwrap() {
-                0
-            } else if &point[dim] > grid[dim].last().unwrap() {
-                grid[dim].len() - 2
-            } else {
-                find_nearest_index(grid[dim].view(), &point[dim])
-            };
+            let lower_idx = locate_lower_index(grid[dim].view(), &point[dim]);
             let interp_diff = (point[dim] - grid[dim][lower_idx])
                 / (grid[dim][lower_idx + 1] - grid[dim][lower_idx]);
             lower_idxs.push(lower_idx);
@@ -123,7 +109,8 @@ where
         let mut interp_diffs = Vec::with_capacity(n);
         for (grid_dim, &point_dim) in data.grid.iter().zip(point.iter()) {
             let step = grid_dim[1] - grid_dim[0];
-            let lower_idx = uniform_lower_index(grid_dim[0], step, grid_dim.len(), point_dim);
+            let lower_idx =
+                locate_lower_index_uniform(grid_dim[0], step, grid_dim.len(), point_dim);
             let diff = (point_dim - grid_dim[lower_idx]) / step;
             lower_idxs.push(lower_idx);
             interp_diffs.push(diff);
@@ -169,7 +156,7 @@ where
         // dimensionality reduction needed — the distance comparison handles exact matches correctly.
         let mut idx = vec![0usize; n];
         for dim in 0..n {
-            let lower_idx = find_nearest_index(data.grid[dim].view(), &point[dim]);
+            let lower_idx = locate_lower_index(data.grid[dim].view(), &point[dim]);
             idx[dim] = if point[dim] - data.grid[dim][lower_idx]
                 < data.grid[dim][lower_idx + 1] - point[dim]
             {
@@ -212,7 +199,7 @@ where
         let n = data.values.ndim();
         let mut idx = vec![0usize; n];
         for dim in 0..n {
-            idx[dim] = step_index(self.dir(dim), data.grid[dim].view(), &point[dim]);
+            idx[dim] = locate_step_index(self.dir(dim), data.grid[dim].view(), &point[dim]);
         }
         Ok(data.values.view()[idx.as_slice()])
     }
@@ -236,7 +223,7 @@ where
         let n = data.values.ndim();
         let mut idx = vec![0usize; n];
         for dim in 0..n {
-            idx[dim] = step_index(StepDirection::Lower, data.grid[dim].view(), &point[dim]);
+            idx[dim] = locate_step_index(StepDirection::Lower, data.grid[dim].view(), &point[dim]);
         }
         Ok(data.values.view()[idx.as_slice()])
     }
@@ -259,7 +246,7 @@ where
         let n = data.values.ndim();
         let mut idx = vec![0usize; n];
         for dim in 0..n {
-            idx[dim] = step_index(StepDirection::Upper, data.grid[dim].view(), &point[dim]);
+            idx[dim] = locate_step_index(StepDirection::Upper, data.grid[dim].view(), &point[dim]);
         }
         Ok(data.values.view()[idx.as_slice()])
     }

src/interpolator/one/strategies.rs

@@ -13,16 +13,13 @@ where
     ) -> Result<D::Elem, InterpolateError> {
         // Extrapolation is checked previously in Interpolator::interpolate,
         // meaning by now, point is within grid bounds or extrapolation is enabled
-        let x_l = if &point[0] < data.grid[0].first().unwrap() {
-            0
-        } else if &point[0] > data.grid[0].last().unwrap() {
-            data.grid[0].len() - 2
-        } else {
-            find_nearest_index(data.grid[0].view(), &point[0])
-        };
-        let x_u = x_l + 1;
-        let x_diff = (point[0] - data.grid[0][x_l]) / (data.grid[0][x_u] - data.grid[0][x_l]);
-        Ok(data.values[x_l] * (D::Elem::one() - x_diff) + data.values[x_u] * x_diff)
+        match locate_axis(data.grid[0].view(), &point[0]) {
+            AxisLocation::Exact(i) => Ok(data.values[i]),
+            AxisLocation::Interp { lower, frac } => {
+                let upper = lower + 1;
+                Ok(data.values[lower] * (D::Elem::one() - frac) + data.values[upper] * frac)
+            }
+        }
     }
 
     /// Returns `true`.
@@ -48,7 +45,7 @@ where
     ) -> Result<D::Elem, InterpolateError> {
         let grid = data.grid[0].view();
         let step = grid[1] - grid[0];
-        let x_l = uniform_lower_index(grid[0], step, grid.len(), point[0]);
+        let x_l = locate_lower_index_uniform(grid[0], step, grid.len(), point[0]);
         let x_u = x_l + 1;
         let x_diff = (point[0] - grid[x_l]) / step;
         Ok(data.values[x_l] * (D::Elem::one() - x_diff) + data.values[x_u] * x_diff)
@@ -70,7 +67,7 @@ where
         data: &InterpData1D<D>,
         point: &[D::Elem; 1],
     ) -> Result<D::Elem, InterpolateError> {
-        let x_l = find_nearest_index(data.grid[0].view(), &point[0]);
+        let x_l = locate_lower_index(data.grid[0].view(), &point[0]);
         let x_u = x_l + 1;
         let i = if point[0] - data.grid[0][x_l] < data.grid[0][x_u] - point[0] {
             x_l
@@ -107,7 +104,7 @@ where
         data: &InterpData1D<D>,
         point: &[D::Elem; 1],
     ) -> Result<D::Elem, InterpolateError> {
-        Ok(data.values[step_index(self.dir(0), data.grid[0].view(), &point[0])])
+        Ok(data.values[locate_step_index(self.dir(0), data.grid[0].view(), &point[0])])
     }
 
     fn allow_extrapolate(&self) -> bool {
@@ -125,7 +122,7 @@ where
         data: &InterpData1D<D>,
         point: &[D::Elem; 1],
     ) -> Result<D::Elem, InterpolateError> {
-        Ok(data.values[step_index(StepDirection::Lower, data.grid[0].view(), &point[0])])
+        Ok(data.values[locate_step_index(StepDirection::Lower, data.grid[0].view(), &point[0])])
     }
 
     /// Returns `false`.
@@ -144,7 +141,7 @@ where
         data: &InterpData1D<D>,
         point: &[D::Elem; 1],
     ) -> Result<D::Elem, InterpolateError> {
-        Ok(data.values[step_index(StepDirection::Upper, data.grid[0].view(), &point[0])])
+        Ok(data.values[locate_step_index(StepDirection::Upper, data.grid[0].view(), &point[0])])
     }
 
     /// Returns `false`.