Fix panic in fx2

examples/cpp/get-subgrids.cpp

@@ -136,11 +136,11 @@ int main() {
 
                         // Check the values of the node entries.
                         assert(node_values_index[0] == 5442.30542919352900); // PyAPI: `subgrid.node_values[0][16]`
-                        assert(node_values_index[1] == 0.03052158400782889); // PyAPI: `subgrid.node_values[1][20]`
-                        assert(node_values_index[2] == 0.03052158400782889); // PyAPI: `subgrid.node_values[2][20]`
+                        assert(node_values_index[1] == 0.03052158400782890); // PyAPI: `subgrid.node_values[1][20]`
+                        assert(node_values_index[2] == 0.03052158400782890); // PyAPI: `subgrid.node_values[2][20]`
 
                         // PyAPI: `grid.subgrid(0, 0, 0).to_array(subgrid.shape)[16][20][20]`
-                        assert(subgrid_array[index] == -4.936156925096015e-07);
+                        assert(subgrid_array[index] == -4.936156925096021e-07);
                     }
                     break;
                 }

examples/fortran/lhapdf_example.output

@@ -1,6 +1,6 @@
  Computing predictions with the same PDF: NNPDF31_nlo_as_0118_luxqed
-   7.1330573367785985E-005   2.1399172010335785E-004
+   7.1330573367785999E-005   2.1399172010335790E-004
  Computing predictions with different PDFs and alphasQ2(NNPDF31_nlo_as_0118_luxqed):
-   7.3091433321743418E-005   2.1927429996523019E-004
+   7.3091433321743418E-005   2.1927429996523024E-004
  Computing predictions with different PDFs and alphasQ2(MSHT20qed_nnlo):
    7.3462246623863024E-005   2.2038673987158908E-004

pineappl/src/interpolation.rs

@@ -22,7 +22,7 @@ mod applgrid {
         for _ in 0..10 {
             let x = (-yp).exp();
             let delta = (1.0 - x).mul_add(-5.0, y - yp);
-            if (delta.abs() < 1e-15) && (delta >= deltap) {
+            if (delta == 0.0) || ((delta.abs() < 2e-15) && (delta.abs() >= deltap.abs())) {
                 return x;
             }
             let deriv = x.mul_add(-5.0, -1.0);
@@ -754,4 +754,20 @@ mod tests {
             assert!(applgrid::fq20(applgrid::ftau0(q2)).ulps(&q2) < 4);
         }
     }
+
+    #[test]
+    fn pr_365() {
+        assert_approx_eq!(
+            f64,
+            applgrid::fx2(6.7865509745),
+            0.1010727499933246,
+            ulps = 4
+        );
+        assert_approx_eq!(
+            f64,
+            applgrid::fx2(6.786550974400577),
+            0.10107275000000002,
+            ulps = 4
+        );
+    }
 }

pineappl/tests/drell_yan_lo.rs

@@ -363,7 +363,7 @@ fn perform_grid_tests(
     let bins = grid.convolve(&mut convolution_cache, &[], &[], &[], &[(1.0, 1.0, 1.0)]);
 
     for (result, reference) in bins.iter().zip(reference.iter()) {
-        assert_approx_eq!(f64, *result, *reference, ulps = 4);
+        assert_approx_eq!(f64, *result, *reference, ulps = 8);
     }
 
     // TEST 5b: `convolve` with `ConvolutionCache::with_two`
@@ -397,8 +397,8 @@ fn perform_grid_tests(
 
     for (&node_value1, &node_value2, &ref_value) in izip!(&node_values[1], &node_values[2], x_grid)
     {
-        assert_approx_eq!(f64, node_value1, ref_value, ulps = 4);
-        assert_approx_eq!(f64, node_value2, ref_value, ulps = 4);
+        assert_approx_eq!(f64, node_value1, ref_value, ulps = 8);
+        assert_approx_eq!(f64, node_value2, ref_value, ulps = 8);
     }
 
     let bins = grid.convolve(&mut convolution_cache, &[], &[], &[], &[(1.0, 1.0, 1.0)]);