Debugging

Debugging inference in RxInfer can be quite challenging, mostly due to the reactive nature of the inference, undefined order of computations, the use of observables, and generally hard-to-read stack traces in Julia. Below we discuss ways to help you find problems in your model that prevents you from getting the results you want.

Getting Help from the Community

When you encounter issues that are difficult to debug, the RxInfer community is here to help. To get the most effective support:

1. Share Session Data: For complex issues, you can share your session data to help us understand exactly what's happening in your model. See Session Sharing to learn how.

2. Join Community Meetings: We discuss common issues and solutions in our regular community meetings. See Getting Help with Issues for more information.

Requesting a trace of messages

RxInfer provides a way that allows to save the history of the computations leading up to the computed messages and marginals in the inference procedure. This history is added on top of messages and marginals and is referred to as a Memory Addon. Below is an example explaining how you can extract this history and use it to fix a bug.

We show the application of the Memory Addon on the coin toss example from earlier in the documentation. We model the binary outcome $x$ (heads or tails) using a Bernoulli distribution, with a parameter $\theta$ that represents the probability of landing on heads. We have a Beta prior distribution for the $\theta$ parameter, with a known shape $\alpha$ and rate $\beta$ parameter.

\[\theta \sim \mathrm{Beta}(a, b)\]

\[x_i \sim \mathrm{Bernoulli}(\theta)\]

where $x_i \in {0, 1}$ are the binary observations (heads = 1, tails = 0). This is the corresponding RxInfer model:

using RxInfer, Random, Plots

n = 4
θ_real = 0.3
dataset = float.(rand(Bernoulli(θ_real), n))

@model function coin_model(x)
    θ  ~ Beta(4, huge)
    x .~ Bernoulli(θ)
end

result = infer(
    model = coin_model(),
    data  = (x = dataset, ),
)

Inference results:
  Posteriors       | available for (θ)

The model will run without errors. But when we plot the posterior distribution for $\theta$, something's wrong. The posterior seems to be a flat distribution:

rθ = range(0, 1, length = 1000)

plot(rθ, (rvar) -> pdf(result.posteriors[:θ], rvar), label="Infered posterior")
vline!([θ_real], label="Real θ", title = "Inference results")

We can figure out what's wrong by tracing the computation of the posterior with the Memory Addon. To obtain the trace, we have to add addons = (AddonMemory(),) as an argument to the inference function. Note, that the argument to the addons keyword argument must be a tuple, because multiple addons can be activated at the same time. Here, we create a tuple with a single element however.

result = infer(
    model = coin_model(),
    data  = (x = dataset, ),
    addons = (AddonMemory(),)
)

Inference results:
  Posteriors       | available for (θ)

Now we have access to the messages that led to the marginal posterior:

RxInfer.ReactiveMP.getaddons(result.posteriors[:θ])

(AddonMemory(Product memory:
 Message mapping memory:
    At the node: Beta
    Towards interface: Val{:out}()
    With local constraint: Marginalisation()
    With addons: (AddonMemory(nothing),)
    With input marginals on Val{(:a, :b)}() edges: (PointMass{Int64}(4), PointMass{TinyHugeNumbers.HugeNumber}(huge))
    With the result: Beta{Float64}(α=4.0, β=1.0e12)
 Message mapping memory:
    At the node: Bernoulli
    Towards interface: Val{:p}()
    With local constraint: Marginalisation()
    With addons: (AddonMemory(nothing),)
    With input marginals on Val{(:out,)}() edges: (PointMass{Float64}(0.0),)
    With the result: Beta{Float64}(α=1.0, β=2.0)
 Message mapping memory:
    At the node: Bernoulli
    Towards interface: Val{:p}()
    With local constraint: Marginalisation()
    With addons: (AddonMemory(nothing),)
    With input marginals on Val{(:out,)}() edges: (PointMass{Float64}(0.0),)
    With the result: Beta{Float64}(α=1.0, β=2.0)
 Message mapping memory:
    At the node: Bernoulli
    Towards interface: Val{:p}()
    With local constraint: Marginalisation()
    With addons: (AddonMemory(nothing),)
    With input marginals on Val{(:out,)}() edges: (PointMass{Float64}(1.0),)
    With the result: Beta{Float64}(α=2.0, β=1.0)
 Message mapping memory:
    At the node: Bernoulli
    Towards interface: Val{:p}()
    With local constraint: Marginalisation()
    With addons: (AddonMemory(nothing),)
    With input marginals on Val{(:out,)}() edges: (PointMass{Float64}(0.0),)
    With the result: Beta{Float64}(α=1.0, β=2.0)
),)

The messages in the factor graph are marked in color. If you're interested in the mathematics behind these results, consider verifying them manually using the general equation for sum-product messages:

\[\underbrace{\overrightarrow{\mu}_{θ}(θ)}_{\substack{ \text{outgoing}\\ \text{message}}} = \sum_{x_1,\ldots,x_n} \underbrace{\overrightarrow{\mu}_{X_1}(x_1)\cdots \overrightarrow{\mu}_{X_n}(x_n)}_{\substack{\text{incoming} \\ \text{messages}}} \cdot \underbrace{f(θ,x_1,\ldots,x_n)}_{\substack{\text{node}\\ \text{function}}}\]

Note that the posterior (yellow) has a rate parameter on the order of 1e12. Our plot failed because a Beta distribution with such a rate parameter cannot be accurately depicted using the range of $\theta$ we used in the code block above. So why does the posterior have this rate parameter?

All the observations (purple, green, pink, blue) have much smaller rate parameters. It seems the prior distribution (red) has an unusual rate parameter, namely 1e12. If we look back at the model, the parameter was set to huge (which is a reserved keyword meaning 1e12). Reducing the prior rate parameter will ensure the posterior has a reasonable rate parameter as well.

@model function coin_model(x)
    θ  ~ Beta(4, 100)
    x .~ Bernoulli(θ)
end

result = infer(
    model = coin_model(),
    data  = (x = dataset, ),
)

Inference results:
  Posteriors       | available for (θ)

rθ = range(0, 1, length = 1000)

plot(rθ, (rvar) -> pdf(result.posteriors[:θ], rvar), fillalpha = 0.4, fill = 0, label="Infered posterior")
vline!([θ_real], label="Real θ", title = "Inference results")

Now the posterior has much more sensible shape thus confirming that we have identified the original issue correctly. We can run the model with more observations, to get an even better posterior:

result = infer(
    model = coin_model(),
    data  = (x = float.(rand(Bernoulli(θ_real), 1000)), ),
)

rθ = range(0, 1, length = 1000)
plot(rθ, (rvar) -> pdf(result.posteriors[:θ], rvar), fillalpha = 0.4, fill = 0, label="Infered posterior (1000 observations)")
vline!([θ_real], label="Real θ", title = "Inference results")

Using callbacks in the infer function

Another way to inspect the inference procedure is to use the callbacks or events from the infer function. Read more about callbacks in the documentation to the infer function. Here, we show a simple application of callbacks to a simple IID inference problem. We start with model specification:

using RxInfer

@model function iid_normal(y)
    μ  ~ Normal(mean = 0.0, variance = 100.0)
    γ  ~ Gamma(shape = 1.0, rate = 1.0)
    y .~ Normal(mean = μ, precision = γ)
end

Next, let us define a syntehtic dataset:

dataset = rand(NormalMeanPrecision(3.1415, 30.0), 100)

Now, we can use the callbacks argument of the infer function to track the order of posteriors computation and their intermediate values for each variational iteration:

# A callback that will be called every time before a variational iteration starts
function before_iteration_callback(model, iteration)
    println("Starting iteration ", iteration)
end

# A callback that will be called every time after a variational iteration finishes
function after_iteration_callback(model, iteration)
    println("Iteration ", iteration, " has been finished")
end

# A callback that will be called every time a posterior is updated
function on_marginal_update_callback(model, variable_name, posterior)
    println("Latent variable ", variable_name, " has been updated. Estimated mean is ", mean(posterior), " with standard deviation ", std(posterior))
end

on_marginal_update_callback (generic function with 1 method)

After we have defined all callbacks of interest, we can call the infer function passing them in the callback argument as a named tuple:

init = @initialization begin
    q(μ) = vague(NormalMeanVariance)
end

result = infer(
    model = iid_normal(),
    data  = (y = dataset, ),
    constraints = MeanField(),
    iterations = 5,
    initialization = init,
    returnvars = KeepLast(),
    callbacks = (
        on_marginal_update = on_marginal_update_callback,
        before_iteration   = before_iteration_callback,
        after_iteration    = after_iteration_callback
    )
)

Starting iteration 1
Latent variable γ has been updated. Estimated mean is 1.01999999999004e-12 with standard deviation 1.4282856856946232e-13
Latent variable μ has been updated. Estimated mean is 3.179424625921506e-8 with standard deviation 9.999999948999998
Iteration 1 has been finished
Starting iteration 2
Latent variable γ has been updated. Estimated mean is 0.009292582887526444 with standard deviation 0.0013012218746582774
Latent variable μ has been updated. Estimated mean is 3.0838963549134513 with standard deviation 1.0318284110284448
Iteration 2 has been finished
Starting iteration 3
Latent variable γ has been updated. Estimated mean is 0.9151862683471093 with standard deviation 0.1281517104742371
Latent variable μ has been updated. Estimated mean is 3.1167424401534207 with standard deviation 0.10452532499731676
Iteration 3 has been finished
Starting iteration 4
Latent variable γ has been updated. Estimated mean is 17.09068078790042 with standard deviation 2.3931739929777094
Latent variable μ has been updated. Estimated mean is 3.1170647600258903 with standard deviation 0.024189063137263496
Iteration 4 has been finished
Starting iteration 5
Latent variable γ has been updated. Estimated mean is 20.672421223568893 with standard deviation 2.8947179728001466
Latent variable μ has been updated. Estimated mean is 3.117067920026215 with standard deviation 0.021993952195300533
Iteration 5 has been finished

We can see that the callback has been correctly executed for each intermediate variational iteration.

println("Estimated mean: ", mean(result.posteriors[:μ]))
println("Estimated precision: ", mean(result.posteriors[:γ]))

Estimated mean: 3.117067920026215
Estimated precision: 20.672421223568893

Using LoggerPipelineStage

ReactiveMP inference engine allows attaching extra computations to the default computational pipeline of message passing. Read more about pipelines in the corresponding section of ReactiveMP. Here we show how to use LoggerPipelineStage to trace the order of message passing updates for debugging purposes. We start with model specification:

using RxInfer

@model function iid_normal_with_pipeline(y)
    μ  ~ Normal(mean = 0.0, variance = 100.0)
    γ  ~ Gamma(shape = 1.0, rate = 1.0)
    y .~ Normal(mean = μ, precision = γ) where { pipeline = LoggerPipelineStage() }
end

Next, let us define a syntehtic dataset:

# We use less data points in the dataset to reduce the amount of text printed
# during the inference
dataset = rand(NormalMeanPrecision(3.1415, 30.0), 5)

Now, we can call the infer function. We combine the pipeline logger stage with the callbacks, which were introduced in the previous section:

result = infer(
    model = iid_normal_with_pipeline(),
    data  = (y = dataset, ),
    constraints = MeanField(),
    iterations = 5,
    initialization = init,
    returnvars = KeepLast(),
    callbacks = (
        on_marginal_update = on_marginal_update_callback,
        before_iteration   = before_iteration_callback,
        after_iteration    = after_iteration_callback
    )
)

Starting iteration 1
[Log]: [NormalMeanPrecision][τ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][τ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][τ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][τ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][τ]: DeferredMessage([ use `as_message` to compute the message ])
Latent variable γ has been updated. Estimated mean is 1.3999999999851476e-12 with standard deviation 7.483314773468494e-13
[Log]: [NormalMeanPrecision][μ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][μ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][μ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][μ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][μ]: DeferredMessage([ use `as_message` to compute the message ])
Latent variable μ has been updated. Estimated mean is 2.233040869412326e-9 with standard deviation 9.9999999965
Iteration 1 has been finished
Starting iteration 2
[Log]: [NormalMeanPrecision][τ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][τ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][τ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][τ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][τ]: DeferredMessage([ use `as_message` to compute the message ])
Latent variable γ has been updated. Estimated mean is 0.01265721523466773 with standard deviation 0.006765566125540312
[Log]: [NormalMeanPrecision][μ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][μ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][μ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][μ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][μ]: DeferredMessage([ use `as_message` to compute the message ])
Latent variable μ has been updated. Estimated mean is 2.7547699184840413 with standard deviation 3.6939351363066044
Iteration 2 has been finished
Starting iteration 3
[Log]: [NormalMeanPrecision][τ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][τ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][τ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][τ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][τ]: DeferredMessage([ use `as_message` to compute the message ])
Latent variable γ has been updated. Estimated mean is 0.09812848835679872 with standard deviation 0.0524518833304538
[Log]: [NormalMeanPrecision][μ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][μ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][μ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][μ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][μ]: DeferredMessage([ use `as_message` to compute the message ])
Latent variable μ has been updated. Estimated mean is 3.126339091275025 with standard deviation 1.4133058870883335
Iteration 3 has been finished
Starting iteration 4
[Log]: [NormalMeanPrecision][τ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][τ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][τ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][τ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][τ]: DeferredMessage([ use `as_message` to compute the message ])
Latent variable γ has been updated. Estimated mean is 0.5752157055944205 with standard deviation 0.30746572768939257
[Log]: [NormalMeanPrecision][μ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][μ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][μ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][μ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][μ]: DeferredMessage([ use `as_message` to compute the message ])
Latent variable μ has been updated. Estimated mean is 3.1790051245355655 with standard deviation 0.5886347921190246
Iteration 4 has been finished
Starting iteration 5
[Log]: [NormalMeanPrecision][τ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][τ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][τ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][τ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][τ]: DeferredMessage([ use `as_message` to compute the message ])
Latent variable γ has been updated. Estimated mean is 1.7972012893270688 with standard deviation 0.9606444971043254
[Log]: [NormalMeanPrecision][μ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][μ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][μ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][μ]: DeferredMessage([ use `as_message` to compute the message ])
[Log]: [NormalMeanPrecision][μ]: DeferredMessage([ use `as_message` to compute the message ])
Latent variable μ has been updated. Estimated mean is 3.1865123043258152 with standard deviation 0.3334073126462098
Iteration 5 has been finished

We can see the order of message update events. Note that ReactiveMP may decide to compute messages lazily, in which case the actual computation of the value of a message will be deferred until later moment. In this case, LoggerPipelineStage will report DeferredMessage.

Using RxInferBenchmarkCallbacks for Performance Analysis

RxInfer provides a built-in benchmarking callback structure called RxInferBenchmarkCallbacks that helps collect timing information during the inference procedure. This structure aggregates timing information across multiple runs, allowing you to track performance statistics (min/max/average/etc.) of your model's creation and inference procedure.

Here's how to use it:

using RxInfer


# Create a benchmark callbacks instance to track performance
benchmark_callbacks = RxInferBenchmarkCallbacks()

# Run inference multiple times to gather statistics
for i in 1:3  # Usually you'd want more runs for better statistics
    infer(
        model = iid_normal(),
        data = (y = dataset, ),
        constraints = MeanField(),
        iterations = 5,
        initialization = init,
        callbacks = benchmark_callbacks
    )
end

In order to nicely display the statistics, you may want to install PrettyTables.jl package. It is not bundled with RxInfer by default, but, if installed manually, it makes the output more readable.

using PrettyTables

# Display the benchmark statistics in a nicely formatted table
PrettyTables.pretty_table(benchmark_callbacks)

RxInfer inference benchmark statistics: 3 evaluations
╭────────────────┬────────────┬────────────┬────────────┬────────────┬───────────╮
│      Operation │        Min │        Max │       Mean │     Median │       Std │
├────────────────┼────────────┼────────────┼────────────┼────────────┼───────────┤
│ Model creation │ 271.057 μs │ 432.248 μs │ 339.217 μs │ 314.347 μs │ 83.424 μs │
│      Inference │  47.047 μs │  78.256 μs │  58.633 μs │  50.595 μs │ 17.087 μs │
│      Iteration │   3.606 μs │  26.570 μs │   7.191 μs │   4.288 μs │  6.241 μs │
╰────────────────┴────────────┴────────────┴────────────┴────────────┴───────────╯

The RxInferBenchmarkCallbacks structure collects timestamps at various stages of the inference process:

• Before and after model creation
• Before and after inference starts/ends
• Before and after each iteration
• Before and after autostart (for streaming inference)

RxInferBenchmarkCallbacks(; capacity = RxInfer.DEFAULT_BENCHMARK_CALLBACKS_BUFFER_CAPACITY)

# Create a callbacks instance to track performance
callbacks = RxInferBenchmarkCallbacks()

# Run inference multiple times to gather statistics
for _ in 1:10
    infer(
        model = my_model(),
        data = my_data,
        callbacks = callbacks
    )
end

# Display the timing statistics (you need to install `PrettyTables.jl` to use `pretty_table` function)
using PrettyTables

PrettyTables.pretty_table(callbacks)

get_benchmark_stats(callbacks::RxInferBenchmarkCallbacks)

DEFAULT_BENCHMARK_CALLBACKS_BUFFER_CAPACITY

This information can be used to:

• Track performance statistics (min/max/average) of your inference procedure
• Identify performance variability across runs
• Monitor the time spent in different stages of inference
• Establish performance baselines for your models
• Detect performance regressions

The timestamps are collected using time_ns() for high precision timing measurements and are automatically formatted into human-readable durations when displayed.