PHP memory limit

[Saaweel]

PHP memory limit

Prevent excessive memory usage when rendering or processing PRT graphs with very deep or cyclic node structures.

Ensure that the same PRT node is not processed more than once inside compute_heuristic_xs() in graph.php.

This avoids unbounded traversal in long chains where each node delegates both true and false branches to the next node, which can otherwise lead to rapid memory growth and PHP hitting the memory limit.

Also:

• Track already-visited PRT nodes during graph traversal.
• Prevent repeated processing of identical nodes.
• Avoid infinite or pathological recursion in deep PRT graphs.
• Preserve existing PRT logic and grading behaviour.

Zulipchat conversation

[sangwinc]

Thanks @Saaweel much appreciated. Could you email me a question which "provoked" this change? It would be good to have one or two really complex questions in the unit testing framework, and these would help.

[Saaweel]

Thanks to you @sangwinc, sure, I'll send you the question right now.