1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
|
; SPDX-FileCopyrightText: 2020 Arvydas Silanskas
; SPDX-FileCopyrightText: 2020 Bradley Lucier
; SPDX-FileCopyrightText: 2024 Peter McGoron
; SPDX-License-Identifier: MIT
(define-syntax proj1
;; Return the first returned value after evaluating `expr`.
(syntax-rules ()
((proj1 expr)
(let-values (((returned second) expr))
returned))))
;;
;; This parameter is defined by the srfi-27 egg.
;;
#;(define current-random-source (make-parameter default-random-source))
(define (with-random-source random-source thunk)
(unless (random-source? random-source)
(error "expected random source"))
(parameterize ((current-random-source random-source))
(thunk)))
;;
;; Carefully return consecutive substreams of the s'th
;; SRFI 27 stream of random numbers. See Sections 1.2 and
;; 1.3 of "An object-oriented random-number package with many
;; long streams and substreams", by Pierre L'Ecuyer, Richard
;; Simard, E. Jack Chen, and W. David Kelton, Operations Research,
;; vol. 50 (2002), pages 1073-1075.
;; https://doi.org/10.1287/opre.50.6.1073.358
;;
(: make-random-source-generator (integer -> (-> *)))
(define (make-random-source-generator s)
(if (not (and (exact? s)
(integer? s)
(not (negative? s))))
(error "make-random-source-generator: Expect nonnegative exact integer argument: " s)
(let ((substream 0))
(lambda ()
(let ((new-source (make-random-source))) ;; deterministic
(random-source-pseudo-randomize! new-source s substream)
(set! substream (+ substream 1))
new-source)))))
;;
;; Primitive randoms
;;
(: make-random-integer-generator (integer integer -> (-> integer)))
(define (make-random-integer-generator low-bound up-bound)
(proj1 (make-uniform-random-integers high: (- up-bound 1)
low: low-bound)))
(: make-random-u1-generator (-> (-> integer)))
(define (make-random-u1-generator)
(make-random-integer-generator 0 2))
(: make-random-u8-generator (-> (-> integer)))
(define (make-random-u8-generator)
(make-random-integer-generator 0 256))
(: make-random-s8-generator (-> (-> integer)))
(define (make-random-s8-generator)
(make-random-integer-generator -128 128))
(: make-random-u16-generator (-> (-> integer)))
(define (make-random-u16-generator)
(make-random-integer-generator 0 65536))
(: make-random-s16-generator (-> (-> integer)))
(define (make-random-s16-generator)
(make-random-integer-generator -32768 32768))
(: make-random-u32-generator (-> (-> integer)))
(define (make-random-u32-generator)
(make-random-integer-generator 0 (expt 2 32)))
(: make-random-s32-generator (-> (-> integer)))
(define (make-random-s32-generator)
(make-random-integer-generator (- (expt 2 31)) (expt 2 31)))
(: make-random-u64-generator (-> (-> integer)))
(define (make-random-u64-generator)
(make-random-integer-generator 0 (expt 2 64)))
(: make-random-s64-generator (-> (-> integer)))
(define (make-random-s64-generator)
(make-random-integer-generator (- (expt 2 63)) (expt 2 63)))
(: clamp-real-number (number number number --> number))
(define (clamp-real-number lower-bound upper-bound value)
(cond ((not (real? lower-bound))
(error "expected real number for lower bound"))
((not (real? upper-bound))
(error "expected real number for upper bound"))
((not (<= lower-bound upper-bound))
(error "lower bound must be <= upper bound"))
((< value lower-bound) lower-bound)
((> value upper-bound) upper-bound)
(else value)))
(: make-random-real-generator
(number number -> (-> float)))
(define (make-random-real-generator low-bound up-bound)
(unless (and (real? low-bound)
(finite? low-bound))
(error "expected finite real number for lower bound"))
(unless (and (real? up-bound)
(finite? up-bound))
(error "expected finite real number for upper bound"))
(unless (< low-bound up-bound)
(error "lower bound must be < upper bound"))
(let ((rand-real-proc (random-source-make-reals (current-random-source))))
(lambda ()
(define t (rand-real-proc))
;; alternative way of doing lowbound + t * (up-bound - low-bound)
;; is susceptible to rounding errors and would require clamping to be safe
;; (which in turn requires 144 for adjacent float function)
(+ (* t low-bound)
(* (- 1.0 t) up-bound)))))
(: make-random-rectangular-generator
(number number number number -> (-> cplxnum)))
(define (make-random-rectangular-generator
real-lower-bound real-upper-bound
imag-lower-bound imag-upper-bound)
(let ((real-gen (make-random-real-generator real-lower-bound real-upper-bound))
(imag-gen (make-random-real-generator imag-lower-bound imag-upper-bound)))
(lambda ()
(make-rectangular (real-gen) (imag-gen)))))
;;; TODO: How to type optional arguments that appear in the front in
;;; CHICKEN?
(define make-random-polar-generator
(case-lambda
((magnitude-lower-bound magnitude-upper-bound)
(make-random-polar-generator 0+0i magnitude-lower-bound magnitude-upper-bound 0 (* 2 PI)))
((origin magnitude-lower-bound magnitude-upper-bound)
(make-random-polar-generator origin magnitude-lower-bound magnitude-upper-bound 0 (* 2 PI)))
((magnitude-lower-bound magnitude-upper-bound angle-lower-bound angle-upper-bound)
(make-random-polar-generator 0+0i magnitude-lower-bound magnitude-upper-bound angle-lower-bound angle-upper-bound))
((origin magnitude-lower-bound magnitude-upper-bound angle-lower-bound angle-upper-bound)
(unless (complex? origin)
(error "origin should be complex number"))
(unless (and (real? magnitude-lower-bound)
(real? magnitude-upper-bound)
(real? angle-lower-bound)
(real? angle-upper-bound))
(error "magnitude and angle bounds should be real numbers"))
(unless (and (<= 0 magnitude-lower-bound)
(<= 0 magnitude-upper-bound))
(error "magnitude bounds should be positive"))
(unless (< magnitude-lower-bound magnitude-upper-bound)
(error "magnitude lower bound should be less than upper bound"))
(when (= angle-lower-bound angle-upper-bound)
(error "angle bounds shouldn't be equal"))
(let* ((b (square magnitude-lower-bound))
(m (- (square magnitude-upper-bound) b))
(t-gen (make-random-real-generator 0. 1.))
(phi-gen (make-random-real-generator angle-lower-bound angle-upper-bound)))
(lambda ()
(let* ((t (t-gen))
(phi (phi-gen))
(r (sqrt (+ (* m t) b))))
(+ origin (make-polar r phi))))))))
(: make-random-boolean-generator (-> (-> boolean)))
(define (make-random-boolean-generator)
(proj1 (make-random-bernoullis)))
(: make-random-char-generator (string -> (-> char)))
(define (make-random-char-generator str)
(when (not (string? str))
(error "expected string"))
(unless (> (string-length str) 0)
(error "given string is of length 0"))
(let* ((int-gen (make-random-integer-generator 0 (string-length str))))
(lambda ()
(string-ref str (int-gen)))))
(: make-random-string-generator (integer string -> (-> string)))
(define (make-random-string-generator k str)
(let ((char-gen (make-random-char-generator str))
(int-gen (make-random-integer-generator 0 k)))
(lambda ()
(generator->string char-gen (int-gen)))))
;;
;; Non-uniform distributions
;;
(: PI float)
(define PI (* 4 (atan 1.0)))
(: make-bernoulli-generator (#!optional number * -> (-> fixnum)))
(define make-bernoulli-generator
(case-lambda
(() (make-bernoulli-generator 1/2 (current-random-real)))
((p) (make-bernoulli-generator p (current-random-real)))
((p source)
(gmap (lambda (x) (if x 1 0))
(proj1 (make-random-bernoullis p: p randoms: source))))))
(: make-binomial-generator (number number -> (-> number)))
(define (make-binomial-generator n p)
(proj1
(make-random-binomials t: n p: p randoms: (current-random-real))))
(: make-categorical-generator
((vector-of number) -> (-> integer)))
(define (make-categorical-generator weights-vec)
(define weight-sum
(vector-fold
(lambda (sum p)
(unless (and (number? p)
(> p 0))
(error "parameter must be a vector of positive numbers"))
(+ sum p))
0
weights-vec))
(define length (vector-length weights-vec))
(let ((real-gen (make-random-real-generator 0 weight-sum)))
(lambda ()
(define roll (real-gen))
(let it ((sum 0)
(i 0))
(define newsum (+ sum (vector-ref weights-vec i)))
(if (or (< roll newsum)
;; in case of rounding errors and no matches, return last element
(= i (- length 1)))
i
(it newsum
(+ i 1)))))))
(: make-normal-generator
(#!optional number number -> (-> number)))
(define make-normal-generator
(case-lambda
(() (make-normal-generator #i0 #i1))
((mean) (make-normal-generator mean #i1))
((mean deviation)
(proj1
(make-random-normals mu: mean sigma: deviation
randoms: (current-random-real))))))
;;; NOTE: Chicken's SRFI-27 has an exponential generator, but for
;;; some reason it is limited to means between 0 and 1.
(: make-exponential-generator (number -> (-> number)))
(define (make-exponential-generator mean)
(unless (and (real? mean)
(finite? mean)
(positive? mean))
(error "expected mean to be finite positive real number"))
(let ((rand-real-proc (random-source-make-reals (current-random-source))))
(lambda ()
(- (* mean (log (rand-real-proc)))))))
(: make-geometric-generator (number -> (-> number )))
(define (make-geometric-generator p)
(proj1
(make-random-geometrics p: p randoms: (current-random-real))))
(: make-poisson-generator (number -> (-> number)))
(define (make-poisson-generator L)
(proj1
(make-random-poissons mu: L random: (current-random-real))))
(: gsampling (#!rest (-> *) -> (-> *)))
(define (gsampling . generators-lst)
(let ((gen-vec (list->vector generators-lst))
(rand-int-proc (random-source-make-integers (current-random-source))))
;remove exhausted generator at index
(define (remove-gen index)
(define new-vec (make-vector (- (vector-length gen-vec) 1)))
;when removing anything but first, copy all elements before index
(when (> index 0)
(vector-copy! new-vec 0 gen-vec 0 index))
;when removing anything but last, copy all elements after index
(when (< index (- (vector-length gen-vec) 1))
(vector-copy! new-vec index gen-vec (+ 1 index)))
(set! gen-vec new-vec))
;randomly pick generator. If it's exhausted remove it, and pick again
;returns value (or eof, if all generators are exhausted)
(define (pick)
(let* ((index (rand-int-proc (vector-length gen-vec)))
(gen (vector-ref gen-vec index))
(value (gen)))
(if (eof-object? value)
(begin
(remove-gen index)
(if (= (vector-length gen-vec) 0)
(eof-object)
(pick)))
value)))
(lambda ()
(if (= 0 (vector-length gen-vec))
(eof-object)
(pick)))))
|
