[Wavepacket-ng-devel] Programming language

[Ulf L. <ul...@wa...>]

Another thing that came to my mind between the project help request and
now is that there is another option for the programming language.

Basically, there are two ways (there are more, but they will not be
more attractive...).

We can use C++, especially C++-11, as suggested in the help request.
There is little to say here. However, an alternative that I came across
would be to use Java.

The advantages, which brought up the whole idea:

+ It has much better integration in IDE's and with testing toolkits
  (JUnit, JMock etc.)

+ It is an easier language for the end user; garbage collection does
  not need to be kind of added, and there are less horrible language
  features than for C++.

+ Deployment is way easier. If we could implement the basic algorithms
  in Java only or find a library, one could have a stand-alone Java
  program in the end. Imagine a course on some quantum mechanics, and
  the students could just download a jar file and write their programs
  without having to compile or care about operating systems and such
  (of course, with a considerable performance penalty, but that might
  not be a big issue for small demo systems and today's computers).

+ Possibly easier scripting language support. I know that at least
  Matlab supports directly importing and working with java objects from
  scratch. Possibly something like this might hold for other scripting
  languages as well.


However, some disadvantages:

- there is some performance penalty associated with the use of Java. I
  once did a search and only found a factor of >= 2 in runtime for raw
  numerics; I have no idea how much the overhead would be for the rest
  of the code.

- I did not find good Java-only numerical libraries. Also, for
  performance reasons, we would have to interface the low-level
  numerical details (matrix handling, FFT and such) with
  platform-dependent code. I have no idea how well this works, what
  quirks there are and so on. Also, the project would then
  probably contain different programming languages, build systems etc.,
  which is kind of ... unaesthetic.

- It might be that for some (large?) setups, setting up a Java Runtime
  environment is not trivial (e.g., parallel computing), so it might be
  that we effectively block this kind of usage. On the other hand, for
  large setups, people will usually write their own wavepacket code
  that is not portable to other problems, but well adapted to the
  targeted problem, which we will have a hard time beating anyway, or
  use a big monster like MCTDH, which is difficult to handle, but can
  handle large problems with additional approximations.


I am not really decided either way, and as written, I have no feeling
for several of the points, so I would put this to discussion and joint
decision. Feel free to discuss and give a verdict. It might also be
that we agree on testing something out, that would also be fine.


Ulf