Revert previous commit and test methods

pineappl/src/empty_subgrid.rs

@@ -18,6 +18,10 @@ impl Subgrid for EmptySubgridV1 {
         Vec::new()
     }
 
+    fn shape(&mut self) -> &[usize] {
+        panic!("EmptySubgridV1 doesn't have a shape");
+    }
+
     fn is_empty(&self) -> bool {
         true
     }
@@ -103,4 +107,10 @@ mod tests {
     fn node_values() {
         assert!(EmptySubgridV1.node_values().is_empty());
     }
+
+    #[test]
+    #[should_panic(expected = "EmptySubgridV1 doesn't have a shape")]
+    fn shape() {
+        let _ = EmptySubgridV1.shape();
+    }
 }

pineappl/src/grid.rs

@@ -205,6 +205,12 @@ impl Grid {
         &mut self.pid_basis
     }
 
+    /// Return a vector containing the interpolation specifications for this grid.
+    #[must_use]
+    pub fn interpolations(&self) -> &[Interp] {
+        &self.interps
+    }
+
     /// Return a vector containing the kinematic specifications for this grid.
     #[must_use]
     pub fn kinematics(&self) -> &[Kinematics] {
@@ -1535,9 +1541,36 @@ mod tests {
     use crate::boc::ScaleFuncForm;
     use crate::channel;
     use crate::convolutions::ConvType;
+    use crate::interpolation::Map;
     use float_cmp::assert_approx_eq;
     use std::fs::File;
 
+    #[test]
+    fn interpolations() {
+        let grid = Grid::new(
+            PidBasis::Pdg,
+            vec![Channel::new(vec![(vec![1, -1], 1.0), (vec![2, -2], 1.0)])],
+            vec![Order::new(0, 2, 0, 0, 0)],
+            vec![0.0, 1.0],
+            vec![
+                Conv::new(ConvType::UnpolPDF, 2212),
+                Conv::new(ConvType::UnpolPDF, 2212),
+            ],
+            v0::default_interps(2),
+            vec![Kinematics::Scale(0), Kinematics::X(0), Kinematics::X(1)],
+            Scales {
+                ren: ScaleFuncForm::Scale(0),
+                fac: ScaleFuncForm::Scale(0),
+                frg: ScaleFuncForm::NoScale,
+            },
+        );
+
+        let interps = grid.interpolations();
+        assert!(matches!(interps[0].map(), Map::ApplGridH0));
+        assert!(matches!(interps[1].map(), Map::ApplGridF2));
+        assert!(matches!(interps[2].map(), Map::ApplGridF2));
+    }
+
     #[test]
     #[should_panic(expected = "channel #0 has wrong number of PIDs: expected 2, found 3")]
     fn grid_new_panic0() {

pineappl/src/import_subgrid.rs

@@ -112,6 +112,10 @@ impl Subgrid for ImportSubgridV1 {
         Box::new(self.array.indexed_iter())
     }
 
+    fn shape(&mut self) -> &[usize] {
+        self.array.shape()
+    }
+
     fn stats(&self) -> Stats {
         Stats {
             total: self.array.shape().iter().product(),

pineappl/src/interp_subgrid.rs

@@ -52,6 +52,10 @@ impl Subgrid for InterpSubgridV1 {
         self.array.is_empty()
     }
 
+    fn shape(&mut self) -> &[usize] {
+        self.array.shape()
+    }
+
     fn merge(&mut self, other: &SubgridEnum, transpose: Option<(usize, usize)>) {
         // we cannot use `Self::indexed_iter` because it multiplies with `reweight`
         if let SubgridEnum::InterpSubgridV1(other) = other {
@@ -261,5 +265,7 @@ mod tests {
         assert_eq!(node_values[0].len(), 23);
         assert_eq!(node_values[1].len(), 1);
         assert_eq!(node_values[2].len(), 1);
+
+        assert_eq!(subgrid.shape(), [23, 1, 1]);
     }
 }

pineappl/src/subgrid.rs

@@ -74,6 +74,9 @@ pub trait Subgrid {
     /// Scale the subgrid by `factor`.
     fn scale(&mut self, factor: f64);
 
+    /// Return the shape of the subgrid
+    fn shape(&mut self) -> &[usize];
+
     /// Assume that the convolution functions for indices `a` and `b` for this grid are the same
     /// and use this to optimize the size of the grid.
     fn symmetrize(&mut self, a: usize, b: usize);