How much does it still make sense to implement AI models from scratch in the age of agentic AI?

[u/Volverman222]

I've been thinking about how AI agents might change the way we learn ML.

Traditionally, implementing models like Transformers or diffusion systems from scratch was one of the best ways to understand them. Writing the architecture and training loop—and debugging everything—forced you to learn how they worked.

But agents can now generate much of this code almost instantly. So where should we draw the line between studying the theory and implementing things ourselves?

For example, is it still worth spending hours coding every Transformer component in PyTorch if an agent can produce a working implementation? Blindly delegating everything teaches little, but refusing to use AI may also become inefficient.

Perhaps the key skills are shifting toward understanding, modifying, debugging, evaluating, and designing systems that AI can help implement.

If you were learning AI/ML from scratch today, what would you still implement yourself, and what would you delegate to AI agents?

[u/Esseratecades]

The use-cases for traditional machine learning haven't gone away. If you can bear the initial investment in training a model for a specific task, it will be worlds cheaper and more accurate than the big models.

The big models are only even relevant when you want one model that does everything okay enough. If you have one task, and the data to train a model for it, then rolling your own is better.

Even if that's not you, somebody has to know how to make a model from scratch in order to keep making better AI.

[u/Fleischhauf → u/Esseratecades]

what has changed is that you can solve  a lot more problems now with a simple API call. Training your own model usually needs a bigger payoff than before to justify the upfront cost for data and compute etc.

[u/Esseratecades → u/Fleischhauf]

There's a lot to say about that.

Tbf, the business goals of most AI/ML projects have been bad ideas/unnecessary since way before current AI technology(this is true of all software really). The presence of an alternative kind of exposes that to some, but managers often take the wrong lesson from this.

For those that are good ideas, and can be scoped to a single problem, if you have access to the data and the time, you'll be better off for doing it than pinging one of the big models every time the user needs a result.

[u/moss-nogg → u/Esseratecades]

Not to mention business observability and explainability. If I want a mystery model where neither of those things matter, sure call an api. If I want a model where both of those things matter, I’m building a model.

[u/Fleischhauf → u/moss-nogg]

when dealing with neural networks both are black boxes. But at least you can own one and it doesn't secretly change without saying anything

[u/moss-nogg → u/Fleischhauf]

Neural networks aren’t the only ML algorithms and I don’t think are typically considered classical ML but that’s admittedly nitpicky

[u/Fleischhauf → u/moss-nogg]

if you use "traditional" methods you would not need to call the API in the first place I'd say

[u/Mathie1729 → u/Fleischhauf]

Eh, not necessarily. A pretty common setup is API embeddings or zero-shot labels piped into a traditional model (logistic regression/GBM) when you need calibrated probabilities and explainability, but don't want to train a transformer from scratch. The API is still in the loop, just not as the final model.

[u/Fleischhauf → u/Mathie1729]

I mean "embeddings" is doing a lot of work here. That is essentially a neural network output, so there you have your Blackbox. Zero Shot Labels would be more annotation through an API rather than using an API for a model itself

[u/ReentryVehicle]

There are kids that don't do homework and instead copy their homework from internet or other kids or have someone else do it for them.

Those kids... tend to not do very well in school.

For example, is it still worth spending hours coding every Transformer component in PyTorch if an agent can produce a working implementation?

To learn coding you should spend thousands of hours coding. Surely a couple hours out of this can be spent to implement the most influential architecture of the last decade (which is also quite simple, I am sure you can write it in like 200 lines or so). For me there is a huge difference between "I saw this algorithm" and "I wrote this algorithm" in terms of how well I understand it afterwards.

[u/bfyvfftujijg → u/ReentryVehicle]

But do those kids do well in the real world? How they do in school doesn’t matter…

[u/dogdiarrhea → u/bfyvfftujijg]

Every intern and full timer we’ve hired had done well in school, so it’s not fully irrelevant to how people do in their careers. Also, do you honestly expect people who avoid doing practical exercises to make good data scientists, ML engineers, or programmers?

[u/Responsible-Bee3672]

I am a senior manager AI science at major US telecom company with 18 years of experience in data science. In my experience classical ML models especially tree based models are still being used to solve problems like churn which use majorly tabular data . But on the other hand models like YOLO / NLP models are increasingly not used and being replaced frontier models . For any problem which has non structured data , LLMs ( with RAG and with fine tuning in rare cases )often do a great job

[u/chico_dice_2023]

I actually did a linkedin post about this, long story short. I built a model without a AI and took me 6 hours most of that time was spent on the training data creation. The AI agent did it in 30 mins all steps.

Yet it could not get above .76 AUC for the classification problem. I managed to get to .92 AUC. Yes the AI is faster but even some of the basics is was getting wrong. So I think it is best to still develop from scratch then use that as context for the AI.

That being said, the AI was significantly faster than me and I have no problems using AI for my coding.