# fun-rec | Recommender system introductory tutorial , online reading

## kandi X-RAY | fun-rec Summary

## kandi X-RAY | fun-rec Summary

Recommender system introductory tutorial, online reading address: https://datawhalechina.github.io/fun-rec/

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### Top functions reviewed by kandi - BETA

- Generate a dynamic RNN cell
- Dynamic RNN loop
- Infer the dtype of the given state
- Return the batch size of the input tensor
- PLE layer
- Process data from csv file
- Generate a CGC layer
- Compute a mixture of experts
- Get statistics from all data
- Generate LGBM classification model
- Fetches user_id and item ids for each item
- Convenience function to add item_items to item_items
- Diagonalized DiEN algorithm
- Concatenate embedding layer
- Build embedding layer
- Build input layers
- Builds DIN layer
- A shared bottom layer
- List user actions
- Core function for Deepfm
- Predict layer
- Computes an ESSM model
- Compute the product of linear features
- Get MTL data
- Generate GBDT model
- Creates training data

## fun-rec Key Features

## fun-rec Examples and Code Snippets

## Community Discussions

Trending Discussions on fun-rec

QUESTION

I'm stuck on how to how to create a statement in SMTLIB2 that asserts something like

...ANSWER

Answered 2021-Apr-14 at 22:30In SMTLib, you'd write that property as follows:

QUESTION

I'm trying to understand how to define an assertion in such a way that it proves certain mathematical qualities of an already defined function. As discussed in this post SMT solvers are not well-suited for induction, which is often needed to prove a mathematical quality.

In my case, I have a recursive function definition for the **identity function** `f(x) = x`

(just as a simple example):

ANSWER

Answered 2021-Jan-29 at 20:04There isn't really much you can do here. Ideally, the strategy would be to define and prove the base case and the inductive-step separately, and then argue (at the meta-level) that the property is true for all strings.

For the base-case things are easy enough. I'd define:

QUESTION

With the following example I am trying to set a constraint on the length of all possible lists in a quantified way. This will lead to a "unsat" result which I am sure is correct.

Can somebody go into detail why this is unsatisfiable and if there is a way around that limitation without putting the length limitation on a specific variable/constant?

I found this interesting thread but my question was not really answered there. In addition, the answers are old and refer to SMT-LIB version 2.0 (and one to a not quantified version). Maybe Z3 is capable to do so nowadays in a way unknown to me.

...ANSWER

Answered 2021-Jan-21 at 20:56This assertion:

QUESTION

The below smt2 code gives an error related to type.

...ANSWER

Answered 2019-Dec-06 at 16:33This is by design. SMTLib's type system isn't designed to do any sort of inference, to make it easy for solvers to unambiguously load specifications. See section 3.6 of http://smtlib.cs.uiowa.edu/papers/smt-lib-reference-v2.6-r2017-07-18.pdf which discusses well-sortedness requirements. So CVC4 rightfully rejects your program.

But you are correct that this is rather annoying in practice. The typical solution is to simply define the required constant at the type you are interested in once and for all:

QUESTION

I'm trying to create a function in Z3 that is transitive but not reflexive. I.e. if `(transitive a b)`

and `(transitive b c)`

hold then `(transitive a c)`

should hold, but `(transitive a a)`

should not.

I've tried to do it the following way, with 5 "tests". The first does what I expect, but the second one fails and results in `unknown`

.

ANSWER

Answered 2019-Sep-04 at 23:52The "verbose" message is a hint here. `mbqi`

stands for model-based-quantifier-instantiation. It's a method of dealing with quantifiers in SMT solving. In the first case, MBQI manages to find a model. But your `transitive`

function is just too complicated for MBQI to handle, and thus it gives up. Increasing the limit will not likely address the problem, nor it's a long term solution.

Short story long, recursive definitions are difficult to deal with, and recursive definitions with quantifiers are even harder. The logic becomes semi-decidable, and you're at the mercy of heuristics. Even if you found a way to make z3 compute a model for this, it would be brittle. These sorts of problems are just not suitable for SMT solving; better use a proper theorem prover like Isabelle, Hol, Coq, Lean. Agda, etc. Almost all these tools offer "tactics" to dispatch subgoals to SMT solvers, so you have the best of both worlds. (Of course you lose full automation, but with quantifiers present, you can't expect any better.)

QUESTION

I'm trying to get z3 to work (most of the time) for very simple non-linear integer arithmetic problems. Unfortunately, I've hit a bit of a wall with exponentiation. I want to be able handle problems like x^{a+b+2} = (x * x * x^{a} * x{b}). I only need to handle non-negative exponents.

I tried redefining exponentiation as a recursive function (so that it's just allowed to return 1 for any non-positive exponent) and using a pattern to facilitate z3 inferring that x^{a+b} = x^{a} * x^{b}, but it doesn't seem to work - I'm still timing out.

...ANSWER

Answered 2018-May-13 at 18:19Pattern (also called triggers) may only contain uninterpreted functions. Since `+`

is an interpreted function, you essentially provide an invalid pattern, in which case virtually anything can happen.

As a first step, I disabled Z3's auto-configuration feature and also MBQI-based quantifier instantiation:

QUESTION

I'm trying to get some values out of Z3 in a way that it queries all available values automatically:

...ANSWER

Answered 2018-Mar-02 at 05:01At this page, I found the following quote:

The

command`eval`

evaluates an expression in the last model produced by Z3. It is essentially executing the"function program"produced by Z3.

Since eval is a `, it follows that it cannot be used within a `

` expression.`

I believe model-enumeration should be easier using some API interface instead of the SmtLibv2 format, as one can easily write a loop that alternates satisfiability checks with learning of a blocking clause that removes previously find solutions from the search space.

QUESTION

I'm trying recursive functions in z3, and I'm curious if there's a bug with model construction. Consider:

...ANSWER

Answered 2017-Mar-09 at 05:44The models used not to reflect the graph of recursive function definitions. So when evaluating recursive functions on values that had not been seen during solving it could produce arbitrary results. This behavior is now changed as the recursive definitions are included in models.

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