Improving Code Generation with Formal Verification
A new tool pairs LLMs and formal verification for safer code creation.
Merlijn Sevenhuijsen, Khashayar Etemadi, Mattias Nyberg
― 6 min read
Table of Contents
- The Problem with Code Generation
- How the New Tool Works
- The Experiment
- How We Generate Code
- Step 1: Initial Code Generation
- Step 2: Code Improvement
- Why This Matters
- The Versatility of Language Models
- Natural Language vs. Formal Requirements
- Assessing Effectiveness
- Results
- Setting Parameters
- The Road Ahead
- Future Aspirations
- Challenges and Limitations
- Conclusion
- Original Source
- Reference Links
Large Language Models (LLMs) are like really smart robots that can understand and write code. They’re great at many things, but sometimes they mess up when writing software that needs to be super reliable. This can be a problem, especially for things like cars or medical devices where a little mistake can lead to big trouble. So, how do we make these LLMs better at writing safe code? Let’s dive into how one tool tries to tackle this challenge.
Code Generation
The Problem withWhen LLMs generate code, they often produce Programs with bugs or behaviors that are not what we want. This is very risky for programs that have to be correct all the time. Think of it this way: would you want a robot surgeon that sometimes forgets how to perform an operation? Probably not!
To fix this, we need to ensure that the code generated by LLMs is correct. This is where Formal Verification comes in. Formal verification checks if a program behaves as expected based on specific rules. Combining LLMs with formal verification helps in automatically generating correct C programs.
How the New Tool Works
Let’s introduce our hero: a new tool that brings together LLMs and formal verification to create reliable C programs. The tool takes a set of instructions written in plain English, some formal guidelines, and a few test cases to generate code.
This process has two main steps. First, the tool makes a few guesses of what the code could look like. Second, it tweaks these guesses based on feedback to improve the code until it works perfectly. If at any point the code meets all the needed requirements, we can consider it correct.
The Experiment
To check if this tool really works, we tested it on 15 programming challenges from a popular competition called Codeforces. Out of these 15, our tool managed to solve 13 of them! Not too shabby for a robot trying to write code.
How We Generate Code
The tool generates code in a structured way. It takes a few inputs: one formal specification (which tells what the program should do), a Natural Language description (in simple English), and some test cases to guide it along.
Step 1: Initial Code Generation
In the first step, the tool makes its best guess at what the code should be based on the provided inputs. It produces several candidate programs, like a chef trying out different recipes. It then checks these programs to see if they compile correctly and meet the expected behavior.
If any of the guesses pass these checks, that means we have a winner! But if none of them do, it moves to step two.
Step 2: Code Improvement
In this step, the tool takes the feedback from its earlier attempts to try and make the code better. It picks the most promising candidate and makes changes based on what it learned from the compiler and the verification tools.
This back-and-forth continues until it either creates a program that checks all the boxes or runs out of chances. It’s like a game of darts: if you keep aiming and adjusting based on where you hit, you’ll eventually hit the bullseye!
Why This Matters
Generating reliable C code automatically is a big deal for software developers. If we can take away some of the burden of coding while ensuring safety, then we can focus on more creative tasks, like inventing the next big app or improving existing software.
Imagine a world where software bugs are a thing of the past. Sounds like a dream, right? With tools like this, we might be a step closer to that reality!
The Versatility of Language Models
These smart models can adapt to various tasks, including code generation. But like we said before, they sometimes trip up, especially in situations where strict rules need to be followed.
Natural Language vs. Formal Requirements
When it comes to generating code, this tool can use both plain English descriptions and formal specifications. The beauty of natural language is that it's easy for us to read and understand. However, formal specifications provide the structure needed for verification, which is crucial for safety-critical applications.
Using both together leads to better results because they complement one another. The natural language helps convey the intent, while the formal requirements keep the generated code on track.
Assessing Effectiveness
In our test, we monitored how well the tool did in creating sidekick code and measured its performance across different specifications.
Results
The results were promising! The tool solved most of the problems on its first attempt and did even better after refinements. This showcases the potential of marrying LLMs with formal verification to make sure our code does exactly what we want it to do.
When looking at total runtimes, we found that combining the two types of specifications was the way to go. It led to quicker problem-solving and less time wasted on unsolved issues.
Setting Parameters
In addition to the specifications, we also looked at various configurations for the tool’s performance. This included how many candidate programs it generated at once, how creative it could be during generation, and whether or not it had an example to learn from.
Interestingly, tweaking these settings helped improve performance. For example, using a lower creativity setting gave fewer solutions, while having an example to refer to sped up the process.
The Road Ahead
While this tool has made significant strides, there’s always room for improvement. For instance, it currently focuses on single-function programs. The next stage in this adventure is to see how it handles more complex scenarios, like multi-function programs or ones that involve loops.
Future Aspirations
We envision a future where this tool can produce safe code for various applications, including those that require more complex logic. By gradually enhancing its capabilities, we can better support developers in creating reliable software that keeps them and the users safe.
Challenges and Limitations
As with any new technology, there are bumps on the road. One major challenge is that our tool depends heavily on the feedback from the verification process. If it can’t verify a program, it may still be correct, but it just won’t know it.
Plus, while the results from our experiments look good, the dataset was small. The more diverse the set of programming problems used for testing, the better we can understand the tool's effectiveness.
Conclusion
To sum things up, we’ve introduced a new tool that combines the brainpower of LLMs with formal verification to generate reliable C code. Through testing, we’ve seen promising results with the tool solving 13 out of 15 programming challenges.
As we look forward, our aim is to continue perfecting this tool so that it can help us create safe and reliable software for various applications. With patience and innovation, we’re excited about what the future holds for automated code generation!
So, are you ready to let robots take over some coding chores? With tools like this, you might find yourself in a world where writing code is a breeze, and you can focus on much more interesting and fun tasks!
Title: VeCoGen: Automating Generation of Formally Verified C Code with Large Language Models
Abstract: Large Language Models (LLMs) have demonstrated impressive capabilities in generating code, yet they often produce programs with flaws or deviations from intended behavior, limiting their suitability for safety-critical applications. To address this limitation, this paper introduces VeCoGen, a novel tool that combines LLMs with formal verification to automate the generation of formally verified C programs. VeCoGen takes a formal specification in ANSI/ISO C Specification Language (ACSL), a natural language specification, and a set of test cases to attempt to generate a program. This program-generation process consists of two steps. First, VeCoGen generates an initial set of candidate programs. Secondly, the tool iteratively improves on previously generated candidates. If a candidate program meets the formal specification, then we are sure the program is correct. We evaluate VeCoGen on 15 problems presented in Codeforces competitions. On these problems, VeCoGen solves 13 problems. This work shows the potential of combining LLMs with formal verification to automate program generation.
Authors: Merlijn Sevenhuijsen, Khashayar Etemadi, Mattias Nyberg
Last Update: Nov 28, 2024
Language: English
Source URL: https://arxiv.org/abs/2411.19275
Source PDF: https://arxiv.org/pdf/2411.19275
Licence: https://creativecommons.org/licenses/by/4.0/
Changes: This summary was created with assistance from AI and may have inaccuracies. For accurate information, please refer to the original source documents linked here.
Thank you to arxiv for use of its open access interoperability.
Reference Links
- https://anonymous.4open.science/r/Vecogen-3008/
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