Add a function for evaluating ψ.

1 files changed, 23 insertions, 0 deletions

diff --git a/brill_data.h b/brill_data.h
index b8b63e8..85e1aac 100644
--- a/brill_data.h
+++ b/brill_data.h
@@ -138,3 +138,26 @@ void bd_context_free(BDContext **bd);
  * @return >= 0 on success, a negative error code on failure
  */
 int bd_solve(BDContext *bd);
+
+/**
+ * Evaluate the conformal factor ψ or its derivatives at the specified rectangular grid.
+ *
+ * @param bd the solver context
+ * @param rho the array of ρ coordinates.
+ * @param nb_coords_rho the number of elements in rho.
+ * @param z   the array of z coordinates.
+ * @param nb_coords_z the number of elements in z.
+ * @param diff_order the order of the derivatives of ψ to evaluate. The first element specifies the
+ *                   derivative wrt ρ, the second wrt z. I.e. diff_order = { 0, 0 } evaluates ψ
+ *                   itself, diff_order = { 0, 1 } evaluates ∂ψ/∂z etc.
+ * @param psi the array into which the values of ψ will be written. ψ is evaluated on the grid
+ *            formed by the outer product of the rho and z vectors.
+ *            I.e. psi[j * nb_coords_rho + i] = ψ(rho[i], z[j]). The length of psi must be
+ *            nb_coords_rho * nb_coords_z.
+ *
+ * @return >= 0 on success, a negative error code on failure.
+ */
+int bd_eval_psi(BDContext *bd, const double *rho, int nb_coords_rho,
+                const double *z, int nb_coords_z,
+                const unsigned int diff_order[2],
+                double *psi);