In many of my Windows batch files, I used the following
construct to detect failures:
do_something
if errorlevel 1 (
echo.An error occurred in do_something
exit /b 1
)
I discovered that it is possible for a Windows program
to exit with a negative integer error code.
This causes the above construct to miss the failure
and the batch file blithely continues.
So I have replaced that construct with
do_something || (
echo.An error occurred in do_something
exit /b 1
)
This way, if the command exits with any nonzero error,
we correctly detect it as a failure.
While trying to convert ecliptic coordinates from mean
equinox of date to true equinox of date, I ran into excessive
overhead from the IAU2000B nutation model. The fact that it
uses 77 trigonometric terms made the calculations a lot slower.
https://apps.dtic.mil/sti/pdfs/AD1112517.pdf
Page 4 in the above document mentions a shorter series
“NOD version 2” that has 13 terms instead of 77 as used in IAU2000B.
I had not noticed NOD2 before, because it appears only in
the FORTRAN version of NOVAS 3.x, not the C version.
After reading the FORTRAN code, I realized NOD2 is the same
as IAU2000B, only it keeps the first 13 of 77 terms.
The terms are already arranged in descending order of
significance, so it is easy to truncate the series.
Based on this discovery, I realized I could achieve all of
the required accuracy needed for Astronomy Engine by
keeping only the first 5 terms of the nutation series.
This tremendously speeds up nutation calculations while
sacrificing only a couple of arcseconds of accuracy.
It also makes the minified JavaScript code smaller:
Before: 119500 bytes.
After: 116653 bytes.
So that's what I did here. Most of the work was updating
unit tests for accepting slightly different calculation
results.
The nutation formula change did trigger detection of a
lurking bug in the inverse_terra functions, which convert
a geocentric vector into latitude, longitude, and elevation
(i.e. an Observer object). The Newton's Method loop in
this function was not always converging, resulting in
an infinite loop. I fixed that by increasing the
convergence threshold and throwing an exception
if the loop iterates more than 10 times.
I also fixed a couple of bugs in the `demotest` scripts.
Changes to the altitude search caused a tiny
change in rise/set times in all the demo programs.
I remembered to update the expected output for
Kotlin, but forgot to do it for Java.
Added the following iterator functions that wrap
search/next pairs of functions:
globalSolarEclipsesAfter
localSolarEclipsesAfter
lunarApsidesAfter
lunarEclipsesAfter
moonNodesAfter
moonQuartersAfter
planetApsidesAfter
transitsAfter
I updated the following Kotlin demos:
MoonPhase.kt ==> moonQuartersAfter
LunarEclipse.kt ==> lunarEclipsesAfter
However, I have not yet figured out how to use these
functions in the corresponding Java demos.
The help pages for the Java and Kotlin demos mention
a Windows batch file `rundemo.bat`, but they did not exist.
I created them, so now the documentation is correct.
Three of the lunar eclipse demos (Python, Java, Kotlin)
provided a less than ideal example of efficient computation.
They were wasting a lunar eclipse search by calculating it
but not printing it. Now after printing exactly 10 lunar
eclipses, stop running immediately.
Added Java demo to search for rise/set/culmination
of the Sun and Moon.
Also added the missing entry for the Kotlin
rise/set/culmination demo that I had forgotten.
Added Kotlin and Java demos for calculating Jupiter's moons.
Illustrates correcting for light travel time.
I added named getters for the 4 moons in `JupiterMoonsInfo`,
because in Java it was really ugly to write
`jm.getMoon()[0]`, etc.
I made the scripts for testing the demos for
C, C#, JavaScript, and Python follow the improved
pattern used for Java and Kotlin: much smaller
and easier to maintain thanks to bash functions.
I also reworked how the Java and Kotlin demos
process errors in the command line arguments.
Using exceptions that are caught by main() rather
than directly exiting the process where the errors
are detected.
I found that it is possible to use the "||" operator
in Windows batch files, and it works the same as the
"||" operator in bash scripts.
This inspired me to rework the bash scripts and
Windows batch files for running the Java/Kotlin demo
tests to be much more compact using functions/subroutines.
The best part is, the new approach will make it much
easier to add more demo tests in the future.
Removed the "now" test from Java demos, because it
does not follow the same pattern as the other demos,
plus it is not really demonstrating astronomy calculations.
Starting working on the Positions.kt demo; but not finished yet.
As I add more Java demos, it will make the code more
compact to factor out argument count checking, etc.
Reworked as a table-driven model instead of using `switch`,
so that I will be able to add new demos more concisely.
Run the Java demo unit test as part of the automated test suite.
If the test fails, print the xml test results to the screen,
so if it happens in GitHub Actions, we can see what went wrong
and diagnose the problem.
This is the first substantial demo of using
the Kotlin version of Astronomy Engine from
a Java program.
Structured the README.md so I can keep adding more and
more demos as separate Java class files.
The `demotest` script builds the code and will run
each demo one at a time, verifying each one's output.
The Kotlin version of Astronomy Engine was using Java
classes like `Date` and `GregorianCalendar`.
Reworked the code to use a completely self-contained
representation of calendar date/time, just like the C version does.
Now Astronomy Engine does not depend on anything outside of
the Kotlin standard library. This should allow us to use
Astronomy Engine for Kotlin Native apps, Web Assembly, etc.
Updated Java demo to use the new method Time.fromMillisecondsSince1970.
Moved the step that creates the fatJar into
the main build process for Kotlin. This is
needed to run the Java demos, and it is good
to fail early if it cannot be built.
Renamed AstroTime to Time.
Renamed AstroVector to Vector.
For some reason this breaks the Java demo build.
I'm pushing the broken build anyway to see if
ebraminio can help me fix it.
Restructured the Java code so we pass in command
line arguments to select which demo we want to run.
We will also pass in date/time, latitude/longitude,
or whatever numeric data we need for future demos.
Automated test run of the Java demos from the
unit test suite.
Adopted from https://stackoverflow.com/a/63332420
So one can run the demo with `./gradlew jar && java -jar build/libs/astronomy-demo-0.0.1.jar`
instead `./gradlew run`
