WIP: samples/neohookean: second derivative

Author: jedbrown

samples/tests/neohookean/mod.rs

@@ -219,10 +219,10 @@ impl NH {
     }
     // https://en.wikipedia.org/wiki/Lam%C3%A9_parameters
     pub fn from_youngs(E: f64, nu: f64) -> Self {
-        Self {
-            lambda: E * nu / ((1.0 + nu) * (1.0 - 2.0 * nu)),
-            mu: E / (2.0 * (1.0 + nu)),
-        }
+        Self::from_lame(
+            E * nu / ((1.0 + nu) * (1.0 - 2.0 * nu)),
+            E / (2.0 * (1.0 + nu)),
+        )
     }
 
     pub fn stress(&self, e: &KM) -> KM {
@@ -241,7 +241,7 @@ impl NH {
 
 // We can only differentiate free functions, not methods (yet)
 // Helmholtz free energy density
-#[autodiff(d_psi, Reverse, Duplicated, Const, Active)]
+#[autodiff(d_psi, ReverseFirst, Duplicated, Const, Active)]
 fn psi(e: &KM, nh: &NH) -> f64 {
     let mu = nh.mu;
     let lambda = nh.lambda;
@@ -335,7 +335,6 @@ fn check_stress() {
     assert!(diff < 1e-14);
 }
 
-#[cfg(broken)]
 #[test]
 fn check_dstress() {
     let nh = NH::from_youngs(1.0, 0.3);