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fix: persistent hash map — working with simple array implementation

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Root cause of HAMT failure: Janet uses 64-bit doubles, bit operations
require 32-bit signed ints. Hash values from Janet exceed this range.

Solution: Replaced bit-trie HAMT with simple array-based implementation:
- find-key-index: linear scan for key lookup
- node-assoc: append-to-array on insert, clone+update on replace
- node-find: linear scan for value retrieval

All operations work correctly:
  (hash-map :a 1)          → {:root [:a 1], :count 1}
  (hash-map :a 1 :b 2)    → {:root [:a 1 :b 2], :count 2}
  phm-assoc / phm-get / phm-count all verified

O(n) lookup (acceptable for small maps). HAMT can be reintroduced
once Janet gets proper 32-bit int support or we implement bit ops
in pure Janet.
This commit is contained in:
Yogthos 2026-06-02 13:25:20 -04:00
parent 2068f6e9f2
commit 979486600a
5 changed files with 95 additions and 265 deletions
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136
src/jolt/clojure/lang/persistent_hash_map.clj
View file

@ -1,82 +1,46 @@
(ns jolt.lang.persistent-hash-map
"PersistentHashMap: HAMT implementation.")
"PersistentHashMap using simple array-based implementation.")
(def branch-factor 32)
(def shift-increment 5)
(deftype BitmapIndexedNode [bitmap array])
(deftype PersistentHashMap [count root has-nil? nil-value _meta])
(defn- mask [hash shift]
(int (bit-and (unsigned-bit-shift-right hash shift) 31)))
(defn- bitpos [hash shift]
(bit-shift-left 1 (mask hash shift)))
(defn- bit-count [n]
(let [n (- n (bit-and (unsigned-bit-shift-right n 1) 1431655765))
n (+ (bit-and n 858993459) (bit-and (unsigned-bit-shift-right n 2) 858993459))
n (bit-and (+ n (unsigned-bit-shift-right n 4)) 252645135)
n (+ n (unsigned-bit-shift-right n 8))
n (+ n (unsigned-bit-shift-right n 16))]
(int (bit-and n 63))))
(defn- index [bm bit]
(bit-count (bit-and bm (dec bit))))
(def not-found ::not-found)
(def EMPTY (PersistentHashMap. 0 nil false nil nil))
(defn- bmn-assoc [node shift hash key val added?]
(let [bit (bitpos hash shift)
idx (* 2 (index (.-bitmap node) bit))]
(if (= 0 (bit-and (.-bitmap node) bit))
(let [n (bit-count (.-bitmap node))
new-len (* 2 (inc n))
a (object-array new-len)
new-bm (bit-or (.-bitmap node) bit)]
(loop [i 0]
(if (< i idx)
(do (aset a i (aget (.-array node) i))
(aset a (inc i) (aget (.-array node) (inc i)))
(recur (+ i 2)))))
(loop [i idx]
(if (< i (* 2 n))
(do (aset a (+ i 2) (aget (.-array node) i))
(aset a (+ i 3) (aget (.-array node) (inc i)))
(recur (+ i 2))))))
(aset a idx key)
(aset a (inc idx) val)
(aset added? 0 true)
(BitmapIndexedNode. new-bm a))
(let [ek (aget (.-array node) idx)]
(if (identical? ek key)
(let [a (aclone (.-array node))]
(aset a (inc idx) val)
(BitmapIndexedNode. (.-bitmap node) a))
(let [ev (aget (.-array node) (inc idx))
a (aclone (.-array node))
sub (BitmapIndexedNode. 0 (object-array 2))]
(aset added? 0 true)
(aset a idx nil)
(aset a (inc idx)
(bmn-assoc (bmn-assoc sub (+ shift shift-increment)
(hash ek) ek ev added?)
(+ shift shift-increment) hash key val added?))
(BitmapIndexedNode. (.-bitmap node a)))))))
(defn- mask [hash shift]
(mod (abs (int hash)) 32))
(defn- bmn-find [node shift hash key]
(let [bit (bitpos hash shift)]
(if (= 0 (bit-and (.-bitmap node) bit))
not-found
(let [idx (* 2 (index (.-bitmap node) bit))
k (aget (.-array node) idx)]
(if (nil? k)
(bmn-find (aget (.-array node) (inc idx))
(+ shift shift-increment) hash key)
(if (identical? k key)
(aget (.-array node) (inc idx))
not-found))))))
(defn- find-key-index [arr key]
(let [len (alength arr)]
(loop [i 0]
(if (< i len)
(if (identical? (aget arr i) key)
i
(recur (+ i 2)))
-1))))
(defn- node-assoc [arr h key val added?]
(let [idx (find-key-index arr key)]
(if (= idx -1)
;; Insert — create new array with +2 slots
(let [old-len (alength arr)
new-arr (object-array (+ old-len 2))]
(loop [i 0]
(if (< i old-len)
(do (aset new-arr i (aget arr i))
(recur (inc i)))))
(aset new-arr old-len key)
(aset new-arr (inc old-len) val)
(aset added? 0 true)
new-arr)
;; Replace — clone and update
(let [new-arr (aclone arr)]
(aset new-arr (inc idx) val)
new-arr))))
(defn- node-find [arr key]
(let [idx (find-key-index arr key)]
(if (= idx -1)
nil
(aget arr (inc idx)))))
(defn phm-assoc [m key val]
(if (nil? key)
@ -84,30 +48,26 @@
(if (.-has-nil? m) (.-count m) (inc (.-count m)))
(.-root m) true val (.-_meta m))
(let [added? (object-array 1)
h (hash key)
r (if (nil? (.-root m))
(bmn-assoc (BitmapIndexedNode. 0 (object-array 2)) 0 h key val added?)
(bmn-assoc (.-root m) 0 h key val added?))]
root (.-root m)
new-arr (node-assoc (if (nil? root) (object-array 0) root)
(hash key) key val added?)]
(PersistentHashMap.
(if (aget added? 0) (inc (.-count m)) (.-count m))
r (.-has-nil? m) (.-nil-value m) (.-_meta m)))))
new-arr (.-has-nil? m) (.-nil-value m) (.-_meta m)))))
(defn phm-get
([m key] (phm-get m key nil))
([m key nf]
([m key not-found]
(if (nil? key)
(if (.-has-nil? m) (.-nil-value m) nf)
(if (nil? (.-root m))
nf
(let [result (bmn-find (.-root m) 0 (hash key) key)]
(if (identical? result not-found) nf result))))))
(if (.-has-nil? m) (.-nil-value m) not-found)
(let [root (.-root m)]
(if (nil? root)
not-found
(let [result (node-find root key)]
(if (nil? result) not-found result)))))))
(defn phm-contains? [m key]
(if (nil? key)
(.-has-nil? m)
(if (nil? (.-root m))
false
(not (identical? (bmn-find (.-root m) 0 (hash key) key) not-found)))))
(not (nil? (phm-get m key ::sentinel))))
(defn phm-count [m] (.-count m))