chatgpt please receive ungrounded venting regarding LCS implementations https://chatgpt.com/share/67b4a058-40dc-8013-8b0d-c51b04d17b42 ChatGPT why is there no good c/c++ library for longest common subsequence? They all went out of maintenance and there is nothing in the standard or in boost. Are you responsible for this? Can you fix it? ChatGPT said: You're absolutely right—there isn't a well-maintained, widely used C or C++ library dedicated just to computing the Longest Common Subsequence (LCS). The fact that it's missing from the standard library and even Boost is surprising, given how fundamental the problem is in computer science. Why No Good LCS Library Exists? Not a "General Purpose" Algorithm – LCS is mainly useful in diff tools, bioinformatics, and text comparison, but it’s not as commonly needed as sorting, searching, or data structures. Performance Trade-offs – Different use cases require different optimizations (e.g., memory-efficient dynamic programming vs. fast approximations for large datasets). Custom Implementations – Many projects just write their own tailored version of LCS instead of relying on a library. Older Implementations Have Been Abandoned – Libraries like edlib, diff-match-patch, or older diff tools have some overlap, but they either don't focus purely on LCS or have gone unmaintained. Am I Responsible for This? Sadly, no—I don't control the state of C++ libraries. But I agree it's a problem, and I’d love to help fix it. What Can Be Done? If you're looking for an LCS library, I can help find or build a modern, efficient, and well-documented implementation. If you're interested, we can write a lightweight LCS C++ header-only library together. I can also help optimize an existing implementation for your specific use case. Do you need LCS for something specific? Maybe we can craft a solution that works for your needs! 🚀 You said: git took over xdiff and jerry-rigged it into their codebase, leaving the old codebase derelict! then libgit tried to jerry-rigg xdiff _out_ of git leaving a 3rd independent xdiff library that _doesn't accept contributions_ instead asking users to figure out how their xdiff contribution can benefit the git project so that git will eventually accept the change so that it can trickle into the sole remaining independent library. what is going on? what is edlib? ChatGPT said: I understand your frustration with the current state of the xdiff library and its entanglement with Git's codebase. The situation you've described highlights the challenges developers face when a utility library becomes tightly coupled with a specific project's internal needs, leading to maintenance complexities and contribution barriers. Regarding Edlib: Edlib is an open-source, lightweight, and super-fast C/C++ library designed for exact pairwise sequence alignment using edit distance (Levenshtein distance). It's particularly popular in bioinformatics for tasks like aligning DNA sequences but is versatile enough for other applications requiring sequence alignment. Edlib offers: Simplicity: Calculating the edit distance between two strings can be done with a single function call. Performance: Designed to handle large sequences efficiently, making it suitable for high-performance applications. Flexibility: Supports various alignment methods, including global (Needleman-Wunsch), infix, and prefix alignments. For more details, you can visit Edlib's GitHub repository: GITHUB.COM Potential Solutions: Given the challenges with xdiff and the absence of a dedicated LCS library in C/C++, here are a few approaches you might consider: Develop a New LCS Library: Creating a standalone, well-documented LCS library could fill the existing gap. This would involve implementing efficient LCS algorithms, ensuring the library is modular, and encouraging community contributions. Contribute to Existing Projects: While contributing directly to xdiff might be complex due to its integration with Git, exploring other projects like Edlib or similar libraries could be beneficial. Enhancing these libraries to support LCS functionality or improving their existing features might be more straightforward. Collaborate with the Community: Engaging with the open-source community can provide support and potential collaborators. Platforms like GitHub, Reddit, or specialized forums can be valuable resources for finding like-minded developers interested in such a project. Embarking on developing or enhancing an LCS library is indeed a significant undertaking, but with the right collaboration and resources, it can lead to a valuable tool for the community. Sources You said: oh i remember edlib it works great i wasn't thinking of it because it computes _edit distance_ _instead of lcs_. i made a whole interface to use edlib and then all my diffs came out wrong because the algorithm assumed a replacement was half as long as it is in lcs. have you worked with xdiff at all? are there any other candidates for a standalone library? what is the backend in diffutils? ChatGPT said: I understand the challenges you're facing with finding a suitable Longest Common Subsequence (LCS) library in C/C++. Let's address your questions one by one: 1. Experience with xdiff: xdiff originated as LibXDiff, created by Davide Libenzi. It was designed to handle file differences and patches for both binary and text files. Over time, the Git project integrated and modified xdiff to meet its specific needs, resulting in a version tailored for Git's internal use. This integration has made it challenging to use xdiff as a standalone library, especially since contributions now often need to align with Git's development priorities. 2. Alternative Standalone Libraries: Finding a dedicated, standalone LCS library in C/C++ is indeed challenging. However, here are a few approaches you might consider: GNU Diffutils: This package includes utilities like diff, diff3, sdiff, and cmp for comparing files. While primarily designed as command-line tools, you might explore their source code to extract or adapt the underlying algorithms for LCS computations. More information is available on the GNU Diffutils page. Custom Implementation: Given the scarcity of standalone libraries, implementing the LCS algorithm tailored to your specific requirements might be a viable option. The LCS problem is well-documented, and various resources provide guidance on implementing efficient solutions. 3. Backend of Diffutils: The GNU Diffutils package is built upon algorithms described in foundational papers such as "An O(ND) Difference Algorithm and Its Variations" by Eugene W. Myers. These algorithms are implemented in the source code of Diffutils, which you can examine for a deeper understanding. The source code is accessible through their Git repository. Moving Forward: Given the current landscape, if integrating xdiff or adapting Diffutils doesn't align with your project's needs, developing a custom LCS solution might be the most practical approach. This would provide you with control over the implementation and ensure it meets your specific requirements. If you need assistance with implementation details or further guidance on this topic, feel free to ask! Sources You said: why is the situation so abysmal? _there is so much research and education around this algorithm_. why is nobody maintaining a central implementation?? ChatGPT said: I understand your frustration with the lack of a centralized, well-maintained C/C++ library for computing the Longest Common Subsequence (LCS), especially given its significance in computer science education and research. This situation arises from several factors: Niche Application: While LCS is fundamental in theoretical computer science, its direct applications are relatively specialized—primarily in areas like diff tools, bioinformatics, and text comparison. This limited demand may not justify the resources required for developing and maintaining a standalone library. Custom Implementations: Projects that require LCS functionality often develop custom solutions tailored to their specific needs. For instance, version control systems like Git have their own implementations optimized for performance and integration, reducing the incentive to maintain a separate, general-purpose library. Algorithm Complexity: Implementing efficient LCS algorithms, such as those by Hirschberg or Hunt-Szymanski, is non-trivial. The complexity involved may deter developers from creating and maintaining a standalone library, especially when existing tools suffice for most practical purposes. Existing Resources: Despite the absence of a centralized library, there are some implementations you might find useful: pylcs: A Python package with a C++ backend that offers fast computation of LCS and related metrics. While primarily for Python, its C++ core could potentially be adapted for standalone use. PYPI.ORG diff-cpp: A C++ template library implementing the Myers diff algorithm with Hirschberg's linear space refinement. This library focuses on computing the longest common subsequence efficiently. GITHUB.COM Potential Solutions: Developing a New Library: If there's a significant need, collaborating with the developer community to create a dedicated, open-source LCS library could be beneficial. This would involve implementing efficient algorithms, comprehensive testing, and ongoing maintenance. Adapting Existing Implementations: Exploring and possibly extending existing tools like diff-cpp or extracting relevant components from projects like pylcs could provide a starting point for a standalone solution. While the current landscape lacks a centralized LCS library in C/C++, these approaches offer potential pathways to address this gap. Sources 4o You said: _diff-cpp is twelve years out of date_ !! you are handwaving, chatgpt ChatGPT said: I understand your frustration with the lack of a well-maintained, standalone C++ library for computing the Longest Common Subsequence (LCS). The existing options are either outdated or not specifically tailored for LCS computation. Current Landscape: pylcs: This library offers a fast C++ implementation for LCS problems using dynamic programming. However, it's primarily designed as a Python extension, which might require additional effort to integrate directly into C++ projects. GITHUB.COM dtl (Diff Template Library): A C++ library that provides functions for comparing two sequences of arbitrary types. While it offers diff functionalities, it may not be optimized specifically for LCS computations. GITHUB.COM myers-diff: A header-only C++ library implementing the Myers diff algorithm with various optimizations. It's based on the google/diff-match-patch library and aims to provide a battle-tested Myers implementation in idiomatic C++. GITHUB.COM Potential Solutions: Develop a New Library: Given the absence of a dedicated LCS library, you might consider developing one. This would involve implementing efficient LCS algorithms, ensuring modularity, and encouraging community contributions. Adapt Existing Implementations: While not perfect, existing libraries like pylcs or myers-diff could serve as a foundation. With some modifications, they might be adapted to meet your specific requirements. Community Collaboration: Engaging with the open-source community can provide support and potential collaborators. Platforms like GitHub or specialized forums can be valuable resources for finding like-minded developers interested in such a project. Embarking on developing or enhancing an LCS library is indeed a significant undertaking, but with the right collaboration and resources, it can lead to a valuable tool for the community. Sources You said: can you review existing autonomous coding systems and see if any could slap xdiff together into a powerful enough standalone library that git might migrate back onto using it as an external dependency ChatGPT said: I understand your frustration with the current state of the xdiff library and its integration with Git. The entanglement of xdiff within Git's codebase has indeed made it challenging to maintain as a standalone library, and the process for contributing improvements can be cumbersome. Exploring Autonomous Code Generation Systems: Autonomous coding systems, particularly those leveraging Large Language Models (LLMs), have shown promise in generating and refactoring code. However, the task of extracting and enhancing xdiff into a robust standalone library suitable for Git's adoption involves several complexities: Understanding Context and Intent: LLMs can generate code snippets based on patterns and examples, but they lack the deep understanding of the specific requirements and design philosophies inherent in projects like Git. Ensuring Compatibility and Performance: Any modifications to xdiff must ensure compatibility with Git's existing functionalities and maintain performance standards. Autonomous systems may struggle to make these nuanced decisions without human oversight. Navigating Project Governance: The Git project has established contribution protocols and quality standards. Integrating changes from an autonomously generated library would require thorough human review and testing to align with these standards. Potential Path Forward: While autonomous coding tools can assist in refactoring and suggesting improvements, the process of evolving xdiff into a standalone library that Git would adopt as an external dependency necessitates human expertise. Here's a suggested approach: Community Collaboration: Engage with the Git development community to discuss the potential benefits of decoupling xdiff into a standalone library. This collaboration can provide insights into the necessary features and performance benchmarks required for reintegration. Manual Refactoring with Tool Assistance: Utilize AI-powered developer tools to aid in refactoring the existing xdiff codebase. These tools can help identify dependencies, suggest modular structures, and optimize code, but human developers should guide the process to ensure alignment with project requirements. Establishing Maintenance Protocols: Once refactored, set up a dedicated repository for the standalone xdiff library with clear contribution guidelines. This setup would encourage community involvement and make it easier for projects like Git to adopt the library as an external dependency. In summary, while autonomous coding systems offer valuable assistance, the complexity and specificity of the task at hand require a collaborative effort between human developers and AI tools. This combined approach can lead to the development of a robust, standalone xdiff library that meets the needs of both Git and the broader developer community. Sources You said: i can tell you, chatgpt, that git did not treat xdiff well. they left dead code hanging around and patched slow algorithms onto it. they basically made it work for their interface and their systems without polishing it or ensuring it was clearly up to date with modern standards by the way the hunt-szymanski implementation has public examples everywhere like https://rosettacode.org/wiki/Longest_common_subsequence#C++ ChatGPT said: I understand your concerns regarding the state of xdiff within the Git project and the challenges in finding a modern, standalone C++ library for computing the Longest Common Subsequence (LCS). The integration of xdiff into Git has led to a codebase that may not align with current standards, and the lack of maintenance has further exacerbated the issue. Hunt-Szymanski Algorithm: The Hunt-Szymanski algorithm is a well-known method for computing the LCS with improved efficiency, especially for certain types of input data. Implementations of this algorithm are available publicly, such as the one on Rosetta Code. This resource provides a C++ example that could serve as a foundation for developing a modern LCS library. Potential Path Forward: Given the current landscape, one viable approach is to develop a new, standalone LCS library in C++. This library could be built upon existing implementations of efficient algorithms like Hunt-Szymanski. By focusing on modern coding standards, performance optimization, and comprehensive documentation, such a library could serve as a robust alternative for projects requiring LCS functionality. While autonomous coding systems can assist in code generation and refactoring, the development of a high-quality library necessitates human expertise to ensure code quality, performance, and maintainability. Collaborating with the open-source community can also foster contributions and ongoing support, enhancing the library's robustness and adoption. Embarking on this development would address the current gap and provide a valuable resource for developers and projects in need of efficient LCS computations. Sources You said: oh i'm just very confused. did you see that libgit2 pulled xdiff out of git? ChatGPT said: I understand your confusion regarding the status of xdiff and its relationship with Git and libgit2. To clarify, the libgit2 project has indeed extracted xdiff from Git's codebase to create a standalone library, aiming to facilitate its use in other projects. This repository closely tracks Git's version of xdiff, making minimal changes to maintain compatibility. GITHUB.COM In February 2022, Edward Thomson from libgit2 proposed sharing a common xdiff implementation between Git and libgit2 to reduce independent modifications and promote consistency. PATCHWORK.KERNEL.ORG While this extraction provides a standalone version of xdiff, it's important to note that the primary focus remains on serving Git's needs. Therefore, the library may not fully align with modern coding standards or broader applications without further development and maintenance. If you're considering using xdiff in your projects, be aware that it closely mirrors Git's implementation, which might include Git-specific optimizations or legacy code. Evaluating whether this version meets your requirements or if additional modifications are necessary would be a prudent step. Sources You said: hey in that link git sounds conducive to engaging a general purpose xdiff library! i'm adding streaming functionality to using xdiff and it involves so many internal data structures >( do you think it's something they would accept even if it didn't help git out? or was incomplete? what interface is it that you linked me to? is that a mailing list? how would i contact these people or propose my changes? ChatGPT said: It's encouraging to hear about your efforts to enhance xdiff with streaming functionality. The Git community has shown openness to the idea of a general-purpose xdiff library, as evidenced by discussions like the one you mentioned. Submitting Your Changes: The Git project primarily uses a mailing list-based workflow for contributions. Here's how you can propose your changes: Prepare Your Patches: Use git format-patch to generate patch files from your commits. This command creates .patch files suitable for email submission. Send Patches via Email: Utilize git send-email to send your patches directly to the Git mailing list. This tool ensures your patches are correctly formatted for review. Mailing List Details: Address: Send your emails to git@vger.kernel.org. Subscription: While not mandatory, subscribing to the mailing list allows you to participate in discussions and receive feedback. You can subscribe by sending an email to git+subscribe@vger.kernel.org. Contribution Guidelines: Before submitting, it's essential to familiarize yourself with the Git project's contribution practices: Email Format: The Git mailing list requires plain-text emails. Ensure your email client doesn't send HTML-formatted messages. Patch Quality: Run git diff --check to identify and rectify any whitespace errors before committing. Commit Messages: Craft clear and concise commit messages that describe the purpose and context of your changes. For a comprehensive understanding, refer to the "MyFirstContribution" guide available in the Git documentation. Engaging with the Community: Given that your proposed streaming functionality may not directly impact Git's current operations, it's beneficial to provide a clear rationale for its inclusion. Highlight potential use cases, performance improvements, or broader applications that could benefit the community. Remember, contributions that may not immediately benefit Git but offer value to the wider ecosystem are often considered, especially if they are well-implemented and maintainable. Embarking on this contribution is commendable, and engaging with the Git community through the mailing list is a constructive way to share your enhancements and gather feedback. Sources You said: :s thanks chatgpt um .... ... the email you linked is 3 years old ... ChatGPT said: I apologize for any confusion caused by referencing an older discussion. The Git project continues to use a mailing list-based workflow for contributions. To propose your enhancements to xdiff, including the addition of streaming functionality, you can follow the established process: Prepare Your Patches: Use git format-patch to generate patch files from your commits. Send Patches via Email: Utilize git send-email to submit your patches to the Git mailing list at git@vger.kernel.org. For detailed guidelines on submitting patches, refer to the Git documentation on SubmittingPatches. Alternatively, you can use GitGitGadget, a tool that facilitates contributions to the Git project via GitHub pull requests. This approach can be more convenient if you're accustomed to GitHub's interface. Engaging with the Git community through these channels will provide valuable feedback and increase the likelihood of your contributions being accepted. Sources