Memoize the flux average the fixture generator computes

benches/reference_scenarios.rs

@@ -10,6 +10,12 @@
 //! scenario. A ratio of times is therefore close to a ratio of per-step cost, which is
 //! the thing worth comparing. If a future scenario's step counts diverge, its timing
 //! ratio means nothing until they are brought back together.
+//!
+//! One scenario is not like for like however the steps come out. Orekit's radiation
+//! pressure registers eclipse event detectors, so its integrator locates the shadow
+//! boundaries by root finding; this crate integrates straight through them. That is work
+//! Orekit does and this does not, and it is arguably the better treatment, so the
+//! radiation row is not purely a speed difference.
 
 use std::path::Path;
 use std::sync::Arc;

scripts/generate-orekit-fixtures.sh

@@ -177,6 +177,13 @@ public class Generate {
      */
     static class UnroundedWeather implements NRLMSISE00InputParameters {
         private final CssiSpaceWeatherData inner;
+        /** One average per day, because that is how often it changes.
+         *
+         * Without this the eighty-one lookups run on every density evaluation, which is
+         * every stage of every step: measured at 279 ms of a 641 ms arc, so the timing
+         * would have been reporting this wrapper rather than Orekit.
+         */
+        private final java.util.Map<Long, Double> cache = new java.util.HashMap<>();
 
         UnroundedWeather(CssiSpaceWeatherData inner) {
             this.inner = inner;
@@ -195,11 +202,19 @@ public class Generate {
         }
 
         public double getAverageFlux(AbsoluteDate date) {
+            long day = (long) Math.floor(date.durationFrom(AbsoluteDate.MODIFIED_JULIAN_EPOCH)
+                    / 86400.0);
+            Double known = cache.get(day);
+            if (known != null) {
+                return known;
+            }
             double sum = 0.0;
             for (int offset = -39; offset <= 41; offset++) {
                 sum += inner.getDailyFlux(date.shiftedBy(offset * 86400.0));
             }
-            return sum / 81.0;
+            double average = sum / 81.0;
+            cache.put(day, average);
+            return average;
         }
 
         public double[] getAp(AbsoluteDate date) {
@@ -558,7 +573,7 @@ public class Generate {
      */
     static void time() throws Exception {
         String[] names = { "two-body", "gravity-8", "gravity-20", "third-body", "radiation",
-                           "drag-harris-priester", "drag-msis" };
+                           "drag-harris-priester", "drag-msis", "drag-msis-plain" };
         for (String name : names) {
             // Build it fresh each run: a propagator carries its state, and reusing one
             // would time a different thing the second time round.
@@ -637,6 +652,17 @@ public class Generate {
                     new OneAxisEllipsoid(EARTH_RADIUS, EARTH_FLATTENING, itrf), BULGE_EXPONENT),
                     new IsotropicDrag(AREA, CD)));
         }
+        if (name.equals("drag-msis-plain")) {
+            // The same thing with CSSI's published average, to show what the recomputing
+            // wrapper costs rather than assuming it is free.
+            p.addForceModel(new DragForce(new NRLMSISE00(
+                    new CssiSpaceWeatherData(CssiSpaceWeatherData.DEFAULT_SUPPORTED_NAMES),
+                    (ExtendedPositionProvider) CelestialBodyFactory.getSun(),
+                    new OneAxisEllipsoid(EARTH_RADIUS, EARTH_FLATTENING, itrf))
+                    .withLocalSolarTimeMode(NRLMSISE00.LocalSolarTimeMode.MEAN)
+                    .withSwitch(9, -1),
+                    new IsotropicDrag(AREA, CD)));
+        }
         if (name.equals("drag-msis")) {
             p.addForceModel(new DragForce(new NRLMSISE00(
                     new UnroundedWeather(new CssiSpaceWeatherData(

tests/fixtures/orekit/msis-drag-low-earth.json

@@ -1451,6 +1451,6 @@
     { "elapsed": 86220.0, "position": [-6.655014145e+06, -1.271109816e+06, 1.780541525e-02], "velocity": [1.438812276e+03, -7.534656147e+03, -2.631428161e-06] },
     { "elapsed": 86280.0, "position": [-6.553405536e+06, -1.719910498e+06, 1.760646718e-02], "velocity": [1.946838261e+03, -7.419614578e+03, -3.997873341e-06] },
     { "elapsed": 86340.0, "position": [-6.421573259e+06, -2.160779117e+06, 1.732600875e-02], "velocity": [2.445880382e+03, -7.270355853e+03, -5.347406004e-06] },
-    { "elapsed": 86400.0, "position": [-6.260125651e+06, -2.591682544e+06, 1.696524000e-02], "velocity": [2.933636216e+03, -7.087569454e+03, -6.673865269e-06] }
+    { "elapsed": 86400.0, "position": [-6.260125651e+06, -2.591682544e+06, 1.696524000e-02], "velocity": [2.933636216e+03, -7.087569454e+03, -6.673865270e-06] }
   ]
 }