Varfar's RedCoder 2

Contents

1. What is it?
2. Screenshot!
3. How does it do it?
4. Feature status
5. Download
6. Which Mars? - if you are interested in programming and specifically in programming Mars emulators, you might be interested in a quick summary I wrote to myself to stop me forgetting what I found when I dug up all the sourcecode I could find..

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What is it?

RedCoder 2 is a graphical MARS Emulator, incorporating a powerful debugger. The graphical nature should make it approachable to newcomers, while the graphical debugging might attract serious corewars devotees. Maybe.

The GUI is written in C++, using the wxWidgets (formerly known as wxWindows) framework. The underlying MARS is a heavily modded C Exhaust 1.9.2 by M Joonas Pihlaja, which has been adapted to be interruptable. It will soon integrate the C pMars parser, as packaged by exMars by Martin Ankerl. It ought be runnable anywhere wxWidgets is, which includes Windows, MacOS, most UNIXs and Linux on most desktop and workstation architectures.

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Screenshot!

^ a very early screenshot of the core-overview window

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How does it do it?

This is the second MARS debugger I have tried to write (Redcoder 1 being the first). I have learnt something about it!

• The MARS is run in-thread, taking cycles away from the GUI display. The MARS pauses when it hits a breakpoint (which include On Writes, On Exec and a stepping mode).
• As the MARS runs, it records an execution log, which can be useful for timescape debugging.
• As an in-thread MARS might lead to a unresponsive UI, the MARS pauses every n cycles to update the GUI and process GUI events (such as STOP; this means that a STOP command may not be honoured immediately, but so what!). The repaint in these interruptions is progressive, based upon the exec-log rather than a full core redraw; this is a major efficiency. The precise number of cycles between repaints can be automatically derived from a "n cycles per second" target in a user interface settings panel, and adjusted automatically to honour this throttling.
• The execution log has a very fine grain; it records precisely the actions being taken, making distinctions possible between: A_PREDEC_A, A_PREDEC_B, A_POSTINC_A, A_POSTINC_B, B_PREDEC_A, B_PREDEC_B, B_POSTINC_A, B_POSTINC_B, SET_A, SET_B, SET_AB, SET_I and EXEC.

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Feature status

Breakpoints
Feature	In Engine	In GUI
On Exec Execution is paused before the instruction executes, but after the operands have been evaluated (which might cause On-Write breakpoints).	2004-02-29	-
On Write Execution is paused after the write has occurred. Writes during operand evaluation (pre-decrementss and post-increments) can be caught, and can even be specifically specified in the condition.	2004-02-29	-
On Read hmm, including indirects?	-	-
Stepping Treated as a special case of On-Exec.	2004-02-29	-
Step thread	n/a	-
Step warrior	n/a	-
Timescape debugging	2004-02-29	-
Editable core	n/a	-
Other focuses to follow..

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Download

Redcoder 2 shall soon be uploaded to CVS, and prebuilt windows binary snapshots will regularly be made available from this very page right here. Redcoder 2 shall be GPLed. Watch this space!

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