Make RFCavity faster

src/elements/RFCavity.H

@@ -187,9 +187,25 @@ namespace RFCavityData
         /** Push all particles */
         using BeamOptic::operator();
 
+        /** Compute and cache the constants for the push.
+         *
+         * In particular, used to pre-compute and cache variables that are
+         * independent of the individually tracked particle.
+         *
+         * @param refpart reference particle
+         */
+        void compute_constants (RefPart const & refpart)
+        {
+            using namespace amrex::literals; // for _rt and _prt
+
+            Alignment::compute_constants(refpart);
+        }
+
         /** This is an RF cavity functor, so that a variable of this type can be used like
          *  an RF cavity function.
          *
+         * The @see compute_constants method must be called before pushing particles through this operator.
+         *
          * @param x particle position in x
          * @param y particle position in y
          * @param t particle position in t
@@ -208,7 +224,7 @@ namespace RFCavityData
             amrex::ParticleReal & AMREX_RESTRICT py,
             amrex::ParticleReal & AMREX_RESTRICT pt,
             uint64_t & AMREX_RESTRICT idcpu,
-            [[maybe_unused]] RefPart const & refpart
+            RefPart const & AMREX_RESTRICT refpart
         ) const
         {
             using namespace amrex::literals; // for _rt and _prt