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Jackdaw is a Common Lisp library for defining and evaluating Bayesian networks and dynamic Bayesian networks with discrete variables that may have deterministic constraints. Its goal is to produce very compact definitions of a wide variety of probabilistic models.

The technical details of this framework are described in chapter three of Van der Weij (2020).

Jackdaw was inspired by the IDyOM modeling framework by Marcus Pearce. The sequence model probability distributions included in jackdaw make use of IDyOM's implementation of the PPM algorithm.

Usage example

The code sample below defines a fully functional implementation of a meter perception model presented in chapter five of Van der Weij (2020). This model is based closely on the model described by Van der Weij, Pearce, and Honing (2017).

(ql:quickload "jackdaw")

(jd::defdistribution meter
    (jd:cpt) (&key normalization-factor meter-cpt) (meter)
  (let ((meter-probability
	  (jd:probability meter-cpt (cons meter nil))))
    (pr:mul (car meter) (pr:div meter-probability normalization-factor))))

    meter (data distribution) (meter) ()
    ((meter-cpt (jd:estimate (jd::make-cpt-distribution) data))
      (apply #'pr:add
	       for meter in (jd:domain (meter-cpt distribution))
	       (pr:mul (car meter)
		       (jd:probability (meter-cpt distribution) (cons meter nil))))))))

(jd:defmodel rhythm (jd:dynamic-bayesian-network)
  (ioi-domain meter-domain)
  ((M                    ; meter
      (jd:cpt ())   ; conditional probability table
      (jd:persist $^m meter-domain))
   (D                    ; downbeat distance
      (^d ^p m)
      (jd:ppms (m)) ; set of PPM sequence models
      (jd:chain (loop for ioi in ioi-domain
			   collect (cons (+ $^p ioi)
					 (jd:ensure-list $^d)))
   (P0                   ; initial phase (or pickup interval)
       (^p0 m)
       (jd:uniform ())
       (jd:persist $^p0 (loop for p below (car $m) collect p)))
   (P                    ; phase
      (^p p0 m d)
      (jd:uniform ())
      (jd:recursive $^p (list (mod (car $d) (car $m)))
			 (list $p0)))
   (I                    ; inter-onset interval
      (d ^p ^i)
      (jd:uniform ())
      (if (jd:inactive? $d) (list jd:+inactive+)
	  (list (- (car $d) $^p))))))

The above first uses DEFDISTRIBUTION to defin a custom categorical probability distribution (which uses the built-in JACKDAW:CPT, an implementation of conditional probability tables). This custom distribution incorporates a factor that compensates for the fact that, in the world of discrete symbolic rhythms, metrical interpretations with longer periods have to spread out probability mass over more possible initial phases. This factor is calculated in the custom estimator defined below with DEFESTIMATOR.

Next, DEFMODEL defines a dynamic Bayesian network graph with five variables (M, D, P0, P, and I), their graphical dependency relations, their probability distributions, and their congruency constraints. For a detailed description of this model, see chapter five of Van der Weij (2020). For the purpose of this example it is useful to know that this model is generates sequences of inter-onset intervals. The first inter-onset interval in such sequences must always be the constant +INACTIVE+, defined in the jackdaw package, since this moment is used to generate the initial phase (or pickup interval).

We can use the REPL to instantiate, estimate, and query the model.

Instantiating the model could be done as follows.

CL-USER> (defparameter
          (make-instance 'rhythm
                         :ioi-domain '(1 2 3 4)
                         :meter-domain '((8 4) (6 4) (6 8))
                         :p0-observer #'first
                         :m-observer (lambda (m) (list (second m) (third m)))
                         :i-observer (lambda (m) (if (listp m) (fourth m) m))))

We have to provide values for the model's two parameters: IOI-DOMAIN and METER-DOMAIN. These should be interpreted as lists of inter-onset intervals and metrical interpretations that the model can generate.

In order to estimate the model, let's create some toy data.

First, we'll create a utility function for annotating sequences of IOIs with metrical information.

(defun rhythm (iois &optional meter phase-0)
  "Utility function for annotating a list of IOIs with initial phase and meter."
  (flet ((annotate (ioi)
	   (cond ((and (null meter) (null phase-0))
		 ((null phase-0)
		  (error "Providing only a meter and no initial phase is not allowed"))
		  (cons phase-0 (append meter (list ioi)))))))
    (mapcar #'annotate (cons jd:+inactive+ iois))))

Now, we can easily jot down some data and estimate the model.

CL-USER> (let ((data (list (rhythm '(4 2 2 4 1 1 1 1 4)           '(8 4) 0)
                           (rhythm '(3 1 1 1 2 1 3 3)             '(6 8) 0)
                           (rhythm '(2 1 1 2 2 1 1 2 2 2 2 1 1 4) '(6 4) 0))))
           (jd:hide *model*) ; hide the entire model
           (jd:observe *model* 'i 'm 'p0)  ; configure I and M to be observed in *MODEL*
           (jd:estimate *model* data)) ; estimate the model from the data

Above, we first used OBSERVE to make the variables I, M, and P0 of the model observable. Providing values for these variables is sufficient to make the model fully observable. Then we used ESTIMATE to estimate the model from the data

The following illustrates how the model instance can be queried on the REPL.

CL-USER> (jd:hide *model*) ; hide all variables
CL-USER> (jd:observe *model* 'i) ; observe inter-onset interval
CL-USER> (jd:probability *model* (rhythm '(1)))
CL-USER> (ql:quickload "cl-ansi-term") ; for nice output formatting
CL-USER> (term:table 
             (jd:generate *model* (rhythm '(4 2 2 4))))
           '(m))) :column-width 12)
|M          |PROBABILITY|
|(8 4)      |0.7039645  |
|(6 4)      |0.24176745 |
|(6 8)      |0.0542681  |

Above, we first used HIDE to make M and P0, the two variables that describe the metrical interpretation of a rhythm, hidden.

Then, we evaluated the model evidence for an (otherwise uninteresting) rhythmic pattern with PROBABILITY.

Finally, we generated model states congruent with a simple rhythmic pattern, defined by the list of inter-onset intervals (4 2 2 4) with GENERATE. We marginalized them to a states containing just the variable M with MARGINALIZE, calculated posterior probabilities with POSTERIOR. The result of these operations is a list of states, which we converted to a probability table with STATE-PROBABILITY-TABLE, and displayed using TABLE from the cl-ansi-term library.


An introductory tutorial to using jackdaw can be found here.


van der Weij, B., Pearce, M. T., and Honing, H. (2017). A probabilistic model of meter perception: Simulating enculturation. Frontiers in Psychology. 8:824. doi: 10.3389/fpsyg.2017.00824

van der Weij, B. (2020). Experienced listeners: Modeling the influence of long-term musical exposure on rhythm perception. (Doctoral dissertation, Universiteit van Amsterdam, Amsterdam) PDF


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