MLDB – Machine Learning Database | Hacker News Reader

MLDB – Machine Learning Database

mldb.ai

103 pointsJPKab10 comments

Not having dug through the code or documentation yet, I'm curious if anyone else knows if this can be used with a minimal memory footprint. The home page touts performance with everything in memory, which is great for blasting through a dataset and then spinning down a $1/hr server. What if I'm willing to accept orders of magnitude slower processing to run this full-time in the background of a low-memory server?

(Founder here).

Could you describe your use-case? This is an interesting question and I'd love to hear more about what you are thinking of.

There are two main parts to most machine learning workloads: training and prediction (though in online scenarios they can be mixed). The training is what tends to be memory intensive, as it involves looking at historical data. Prediction, especially in real-time, is typically less memory intensive and more suited to your scenario. It is possible with MLDB to have training and prediction on separate instances to optimize hardware cost.

Our focus to date has been on getting large real-world use cases to fit, for both training and prediction, on a single commodity server with decent amounts of RAM (4GB and up), especially for training. Performance there is good; you can train user scorers or recommenders over hundreds of millions of users with 20 billion historical actions in minutes on a single server. We haven't focused much on the absolute memory footprint and there is some overhead; you will need a server with a good amount of memory, a couple of gigs, to have a pleasant user experience.

(edit): The team tells me it will work decently down to 256MB of RAM or so, for carefully designed automated workloads. For interactive use you will want more RAM.

I appreciate the detailed response! My use case is yet another indie web, run-your-own-server kind of thing that processes content my friends post online (from tweets to shared articles) and can predict whether or not it is relevant to me based on extracted topics, source, my context/location, and whatnot. Both the source data and training data comes in at a trickle (though I'm pondering ways to propagate training data throughout friend-of-friend networks) and is processed in the background rather than on-demand, so my performance characteristics are very different than most of the use cases I've seen.

I'm trying to keep the system frugal with memory but liberal with persistent storage, since you can run a commodity instance 24/7 and mount a pretty large volume for fairly cheap. It'll be slow, for sure, if there's only one user for each installation it won't need to worry about handling many queries per second.

It seems that MLDB would be a decent fit for this use-case. You would be able to do pre-processing in the background continuously, and predictions could do a significant amount of work on-demand. Depending upon the size of the overall training set, you might need to spin up a larger server for an hour or so to retrain a model... but if you set the system up right, the model would only need to be trained infrequently as most of the work would be done online. The more preprocessing you can do in the background, the richer and smaller the data that would go into the training phase.

MLDB can memory-map some kinds of datasets which would also help with the low memory-to-datasest size ratio.

Please feel free to reach out (jeremy at datacratic) if you'd like to discuss further.

How does this compare to RecDB, other than being commercial? http://www-users.cs.umn.edu/~sarwat/RecDB/

(MLDB product lead here)

I hadn't seen RecDB, thanks for the link! At a glance, other than the licensing, the main point of comparison is that MLDB is more powerful/general-purpose than RecDB, as it provides primitives for not only for creating recommenders but to do other machine-learning tasks like classification, clustering, dimensionality reduction, visualization etc. MLDB also seems to have a bit more documentation :)

I've used madlib[1] before and was quite happy with that. Maybe you can do a feature comparison with similar existing solutions as many people don't have the bandwidth to go through your documentations.

[1] http://madlib.net/

That's a good idea, thanks! What kinds of problems were you solving with madlib?

Classification problems in a medical domain. It literally took me 30 minutes to install madlib and run logistic regression on a table. It then probably took me a few more days to do some analysis, try out various algorithms and productionize the predictor.

A feature comparison with other solutions is a great idea. We'll work on that and share here.

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