REVIEW 3 major objections 5 minor 17 references
Evaluating Code Generation of LLMs in Advanced Computer Science Problems
T0 review · 3 major / 5 minor · reviewed 2026-08-16 · deepseek-v4-flash
Pith's one-line read The paper claims LLMs are highly effective at introductory programming assignments but rarely solve advanced CS4/CS5 assignments, and that they tend to identify the underlying algorithm while ignoring constraints.
desk verdict Useful extension of LLM assignment-benchmarking to advanced CS, but the TSP verifier overstates two of the three 'correct' advanced results; central gap claim still holds. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The evaluation rests on a three-part prompt (problem description, input format, output format) fed to each tool, followed by automated verification: a Verifier computes the reference answer for each of 1000 random instances, and accuracy is the fraction of instances the generated program answers correctly. A problem is considered solved only when accuracy is 100%; for problems with multiple valid answers, such as TSP, the verifier checks structural properties of the answer instead of a single number. This machinery matters because every conclusion about LLM capability is defined by it, and it turns vague impressions of coding skill into a countable score across languages and tools.
What would settle it
Run the paper's nine advanced prompts through a newer LLM and grade against the original courses' hidden test suites. If most generated programs pass those suites, the central claim that advanced CS assignments are rarely solved would be weakened.
Extended reading notes
Core claim
The paper's central discovery is a sharp drop in correctness exactly where courses stop teaching basic syntax and start teaching algorithm design. Using accuracy defined as the share of correctly verified test cases, with a problem counted as solved only at 100%, the models solved the CS1 baseline problems almost everywhere, including perfect scores for the shortest-path baseline, but almost never solved the nine CS4/CS5 problems. In the advanced set, Github Copilot produced the only perfect solutions, while the other tools mostly generated heuristics, solutions that solved a simplified version of the prompt, or code that did not run. The authors conclude that LLMs are good at naming and sketching the textbook algorithm but weak at conforming to the constraints that make an assignment a genuine test of understanding.
Load-bearing premise
The whole comparison assumes that the authors' reference solutions are error-free and that 1000 random test cases are representative enough of what an advanced course would actually test.
Editorial extensions
If this is right
- Instructors can no longer assume that textbook algorithm assignments are LLM-proof: the tools recognize the underlying problem and return plausible code, so assessment must probe constraints and edge cases.
- Adding a single problem-specific constraint, as in the TV-Zapping problem, drove accuracy down to 96.4 percent at best and near zero for most tools, indicating that constraint variation is an effective way to make assignments harder for LLMs.
- GitHub Copilot was the only tool to produce any perfect advanced solutions, while the other tools more often produced non-functional code or heuristics.
- C code was the most fragile, with twelve compilation or runtime errors across the advanced problems, so language choice materially changes what a student gets from a tool.
- Students using LLMs on advanced work will frequently receive partially correct code that passes easy cases, which makes hidden-constraint testing important for fair grading.
Reading between the lines
- The perfect scores on TSP and Cut Boards should be read cautiously: for NP-hard problems the random test generator must keep instances small enough to verify exhaustively, so larger or adversarial instances could reveal failures that the paper's 1000-case suites do not.
- Because the dominant failure pattern is ignoring constraints, a cheap robustness experiment would be to move a constraint sentence earlier or later in the prompt and measure accuracy shifts; if placement matters, students could game tools by rewording assignments.
- A likely next step is repair: since many generated solutions are close, feeding failing test outputs back to the model could convert some partial solutions into correct ones, which would raise the effective usefulness of the tools beyond the paper's one-shot accuracy.
- The paper's setup amounts to a constraint-adherence benchmark; if the pattern generalizes, advanced CS assignments could serve as a practical testbed for measuring how well LLMs follow multi-part instructions.
Signed reviews
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. This paper evaluates the code-generation performance of four LLM tools (GitHub Copilot, CodePal, Llama3-70b, and Mistral-Nemo) on twelve programming problems: three introductory CS1 problems as a baseline and nine advanced CS4/CS5 problems, each in Java, Python, and C. For each problem, the authors generate 1000 random test cases, run the generated programs against those tests, and compare the outputs with their own reference solutions, defining accuracy as the fraction of correctly solved test cases and correctness as 100% accuracy. The main empirical finding is that LLMs solve most introductory problems but rarely solve advanced assignments correctly; however, they often produce partial solutions or recognize the underlying algorithm. The paper also reports tool- and language-level differences, concluding that GitHub Copilot outperforms the other tools and that C causes the most errors.
Significance. If the results hold, this is a useful empirical contribution to the growing literature on LLMs in computing education, complementing earlier work that focused on introductory programming. The study's strengths include a handpicked problem set spanning multiple institutions and levels, a handwritten baseline problem to reduce memorization risk, a public repository with prompts and data, and clear operational definitions of accuracy and correctness. The central qualitative claim—that LLMs are far more successful on introductory than advanced assignments—is visible in Table 2 and is robust to the specific verifier weaknesses discussed below. However, the quantitative strength of the claims is limited by unresolved verification and statistical issues, so the paper needs revision before its specific numbers can be taken at face value.
major comments (3)
- [4.4, Table 2, P5 (TSP)] The Traveling Salesman Problem verifier checks feasibility only, not optimality. Section 4.4 states that for problems with many valid answers, 'such as the Traveling Salesman Problem (TSP) problem', the verification step 'checks each aspect of the given answer, such as verifying all nodes exist in a path and that bounds are not exceeded.' The TSP assignment asks for the shortest route, so a feasible Hamiltonian tour is not a correct solution. Consequently, the two 100% accuracy cells for TSP (Copilot in Python and Copilot in Java) do not establish that those programs solve the assignment. Since the paper reports only three advanced-problem combinations with 100% accuracy, and two of them are TSP, the specific RQ1 count is overstated. The paper should either verify optimality against an exact solver (e.g., exhaustive search on the same small instances) or re-classify these cells.
- [4.4, Definition 1, Table 2] Accuracy is reported as a point estimate with t=1000 test cases and no variance across test-generation seeds. The test cases for all solutions use the same random seed per problem, so the reported differences between tools and languages (e.g., P5 Python: Copilot 100 vs CodePal 0; P7 Java: Copilot 0 vs Llama 77.4) could change substantially under a different seed, especially for NP-hard problems where instance-size distributions matter. This lack of error bars or confidence intervals weakens the quantitative comparisons in RQ3 and the partial-solution thresholds used in Section 5.3 (e.g., accuracy > 5%). The authors should run multiple test seeds and report variances, or at minimum justify why a single seed is representative.
- [4.4 and 6] The test-suite generation process is not described in enough detail to assess whether the 1000 random cases are representative of real assignments. For NP-hard problems like Boxes and TSP, the instances must be small enough for exhaustive verification, so the difficulty distribution may differ from typical course assignments. Moreover, the reference solutions are assumed correct without supporting evidence; a bug in any reference solution would shift every accuracy in Table 2. The manuscript should document the instance-generation parameters, the input distributions, and the verification logic per problem, and should make the reference solutions and generators available for inspection alongside the existing prompt/data repository.
minor comments (5)
- [5.1] The sentence 'Among P4 to P12, only P4,TSP and P11, Cut Boards, have two and one correct results, respectively' mislabels the TSP problem as P4; TSP is P5 according to Table 1.
- [5.3] The text 'it seems that CP in Python generates the same heuristic as CG in C' should read 'GC' instead of 'CG' for GitHub Copilot.
- [Listing 1.1] Listing 1.1 contains stray semicolons in Python code (e.g., 'return b o x e s _ n e e d e d ;'), which are likely transcription artifacts; the code should be cleaned up to match what was actually executed.
- [2 Related Work] The sentence 'Their results show that the ACG performs better than students in this course Finnie-Ansley et al..' is grammatically incomplete and has a duplicated period; it should be rewritten and properly cited.
- [Table 2 header] The table header is visually ambiguous: the HF column is split into LL and MS subcolumns, making it look like five tools rather than four. Use a clearer multi-row header that groups Llama and Mistral under a single Hugging Face tool category.
Circularity Check
No significant circularity: the paper reports a direct empirical measurement against independently written reference solutions.
full rationale
This paper is an empirical evaluation, not a derivation. The central claim—that LLMs solve CS1 assignments better than CS4/CS5 assignments—is supported by running generated programs against 1000 random test cases per problem and comparing outputs with the authors' reference solutions, as described in Section 4.4. No parameter is fitted to a subset of the data and then used to predict a closely related quantity; correctness is defined directly in Definitions 1 and 2, and the accuracy values in Table 2 are measured results rather than consequences of the definition. The bibliography contains no work by Catir, Claesson, or Tsoupidi, so no load-bearing premise is justified only by a self-citation, and no uniqueness theorem or ansatz is imported from the authors' own prior papers. The one notable weakness is that, for problems with many valid answers such as TSP, the verifier checks feasibility ('all nodes exist in a path and that bounds are not exceeded') rather than optimality, which threatens the validity of individual 100% TSP cells; however, this is an evaluation-validity concern, not circularity, and it cuts against the paper's advanced-problem difficulty claim only by potentially over-crediting LLMs. Even discounting both TSP cells, the qualitative gap between CS1 and CS4/CS5 remains, so the central claim does not reduce to the paper's own inputs by construction.
Assumptions & free parameters
free parameters (3)
- Test suite size t =
1000
- Floating-point tolerance =
0.1
- Partial-solution accuracy threshold =
>5%
assumptions (3)
- domain assumption The reference solutions are correct implementations of the problems.
- domain assumption Randomly generated test cases are representative of the problem space.
- domain assumption Manual modifications to generated code do not alter the algorithm.
Cite this review
Pith. "Pith review of Evaluating Code Generation of LLMs in Advanced Computer Science Problems." pith.science (2026). https://pith.science/paper/TUZODANP
@misc{pith2026250414964,
author = {Pith},
title = {Pith review of: Evaluating Code Generation of LLMs in Advanced Computer Science Problems},
year = {2026},
howpublished = {\url{https://pith.science/paper/TUZODANP}},
note = {Machine review of arXiv:2504.14964}
}
read the original abstract
Large Language Models (LLMs), such as GitHub Copilot and ChatGPT have become popular among programming students. Students use LLMs to assist them in programming courses, including generating source code. Previous work has evaluated the ability of LLMs in solving introductory-course programming assignments. The results have shown that LLMs are highly effective in generating code for introductory Computer Science (CS) courses. However, there is a gap in research on evaluating LLMs' ability to generate code that solves advanced programming assignments. In this work, we evaluate the ability of four LLM tools to solve programming assignments from advanced CS courses in three popular programming languages, Java, Python, and C. We manually select 12 problems, three problems from introductory courses as the baseline and nine programming assignments from second- and third-year CS courses. To evaluate the LLM-generated code, we generate a test suite of 1000 test cases per problem and analyze the program output. Our evaluation shows that although LLMs are highly effective in generating source code for introductory programming courses, solving advanced programming assignments is more challenging. Nonetheless, in many cases, LLMs identify the base problem and provide partial solutions that may be useful to CS students. Furthermore, our results may provide useful guidance for teachers of advanced programming courses on how to design programming assignments.
Figures
Reference graph
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No changes were made to the algorithms of the solutions
to lower the runtime of the programs. No changes were made to the algorithms of the solutions. Table 3 list all solutions that had some changes made before running the tests. There were four different types of changes made. The most common change Evaluating Advanced Course Ass...
Reviewed August 16, 2026 · model on record in the stance chip above.
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