This work was sponsored by enioka.

The task one is:

Given a finite set of objects

`pool`

, and an object`query`

. Look, which ever comes first, within approximately`t`

time, or at most`n`

objects subset of`pool`

that are near`query`

according to the metric`m`

, call that subset`candidates`

.

Most popular approach nowadays, and the one I could start to get under control is to rely on Hierarchical Navigable Small Worlds. HNSW is reminiscent of Ben Goertzel glocals from opencog fame.

HNSW datastructure use a deterministic heuristic with the distance function to construct clusters, still, it use random to spread pression on memory, and compute. It looks like a skip-list with multiple path ways. A regular natural sort will not speed queries, because of that glocals are not sorted, instead nodes are related to points in a higher level layer. The higher the level the less points they are. The highest level has only one point. Each point has a maximum `x`

neighbor in a lower level. Horizontal navigation must be done through the parent point.

While I put that whole on a flashcard, you can delice with the following brute force algorithm that will generate a pool of points nearest to a point `query`

:

```
(import (chezscheme))
(import (letloop r999))
(import (scheme generator))
;; brute force algorithm
(define total (string->number (or (getenv "HYPER_TOTAL") "65536")))
(define exponent (string->number (or (getenv "HYPER_EXPONENT") "8")))
(define pk
(lambda args
(write args)
(newline)
(car (reverse args))))
(define point-distance
(lambda (a b) (abs (- a b))))
(define point-random (lambda () (random (expt 2 exponent))))
(define pool (map (lambda _ (point-random)) (iota total)))
(define query (point-random))
(define ~.two
(lambda (x)
(inexact (/ (round (* x 100)) 100))))
(define candidates
(let* ((objects (map (lambda (x) (cons (point-distance query x) x)) pool))
(objects* (sort (lambda (u v) (< (car u) (car v))) objects))
(distance-max (apply max (map car objects*))))
(map (lambda (x) (cons (~.two (/ (- distance-max (car x)) distance-max))
(cdr x)))
objects*)))
(pk 'query (string-upcase (number->string query 36)) query)
(newline)
(for-each pk (map (lambda (x) (list (car x) (number->string (cdr x) 36) (cdr x))) candidates))
```