I made minimum modifications to get the SRFI and the test program to
work on Gambit (git diff results below).

Two tests are failing:

             (reset-source!*)
             (test-sphere (make-sphere-generator 1) (vector 1.0 1.0) 200
#t)  ;; <<<<<<<<<<<<<<
             (test-sphere (make-sphere-generator 2) (vector 1.0 1.0 1.0)
200 #t)
             (test-sphere (make-sphere-generator 3) (vector 1.0 1.0 1.0
1.0) 200 #t)

             (reset-source!*)
             (test-sphere (make-ellipsoid-generator (vector 1.0 1.0))
(vector 1.0 1.0) 200 #t) ;; <<<<<<<<<<<
             (test-sphere (make-ellipsoid-generator (vector 1.0 1.0
1.0)) (vector 1.0 1.0 1.0) 200 #t)
             (test-sphere (make-ellipsoid-generator (vector 1.0 1.0 1.0
1.0)) (vector 1.0 1.0 1.0 1.0) 200 #t)

Now reset-source!* is defined as

(define (reset-source!*)
   (random-source-pseudo-randomize! (current-random-source) 0 0))

i.e., it resets the current-random-source to the initial state of the
random number generator (in Gambit's case the SRFI 27 generator).

So, since (make-ellipsoid-generator (vector 1.0 1.0)) is exactly
(make-sphere-generator 1), these two sets of tests are identical, so if
one fails, the other one does, too.

The failure is:

"sphere-test.scm"@78.5-78.27: FAILED (test-assert (< zz 1)) GOT #f
*** 1 test failed after 688 tests

and the value of zz is 1.070418545004296.

The test passes if I take 400 samples instead of 200 samples.

I don't understand the reasoning behind this test, which checks that the
norm of the sum of the samples is < (\pi/2) * sqrt(number-of-samples).
Can someone give an explanation or a pointer?

Brad

heine:/tmp/srfi-194> gsi . srfi-194-test.scm
testing srfi-194
| testing Test clamp real number
| testing Test with-random-source basic syntax
| testing Test make-random-source-generator
| testing Test random int
| testing Test random real
| testing Test complex rectangular
| testing Test complex polar
| testing Test random bool
| testing Test random char
| testing Test random string
| testing Test Bernoulli
| testing Test categorical
| testing Test poisson
| testing Test normal
| testing Test exponential
| testing Test geometric
| testing Test uniform sampling
| testing Test Zipf sampling
| testing Test sphere
1.070418545004296
"sphere-test.scm"@78.5-78.27: FAILED (test-assert (< zz 1)) GOT #f
*** 1 test failed after 688 tests
heine:/tmp/srfi-194> git diff
diff --git a/sphere-test.scm b/sphere-test.scm
index a394322..6831fc9 100644
--- a/sphere-test.scm
+++ b/sphere-test.scm
@@ -74,6 +74,7 @@

    (define (check-zero samples)
      (define zz (norm-should-be-zero samples))
+    (pp zz)
      (test-assert (< zz 1)))

    ; maximum allowed tolerance for radius deviation
diff --git a/srfi-194-test.scm b/srfi-194-test.scm
index b066f91..06f45ed 100644
--- a/srfi-194-test.scm
+++ b/srfi-194-test.scm
@@ -13,7 +13,7 @@
    (scheme write)
    (srfi 1)
    (srfi 27)
-  (srfi 133)
+  #;(srfi 133)
    (srfi 194))

  (cond-expand
@@ -137,7 +137,9 @@
                                     (lambda ()
(make-random-integer-generator 0 10)))
                                   5))
                          '(4 9 7 9 0)))
-                (apply test-multiple-sources multiple-sources-testcase))))
+                (apply test-multiple-sources multiple-sources-testcase)))
+  (else
+   #f))

  (test-group "Test make-random-source-generator"
              (reset-source!)
diff --git a/srfi/194.scm b/srfi/194.scm
index fa875d7..3721e8d 100644
--- a/srfi/194.scm
+++ b/srfi/194.scm
@@ -2,13 +2,14 @@
  ; SPDX-License-Identifier: MIT

  (define-library (srfi 194)
-  (import (scheme base)
+  (import (gambit) ;; (scheme base)
            (scheme case-lambda)
            (scheme inexact)
            (scheme complex)
            (scheme write)
            (srfi 27)
-          (srfi 133))
+          #;(srfi 133)
+          )

    (cond-expand
      ((library (srfi 158)) (import (srfi 158)))
diff --git a/zipf-test.scm b/zipf-test.scm
index 47c8cfa..9a34bd4 100644
--- a/zipf-test.scm
+++ b/zipf-test.scm
@@ -64,7 +64,8 @@

    ; Sequence 1..NVOCAB
    (define seq
-    (vector-unfold (lambda (i x) (values x (+ x 1))) NVOCAB 1))
+    #;(vector-unfold (lambda (i x) (values x (+ x 1))) NVOCAB 1)
+    (list->vector (iota NVOCAB 1)))

    ; Sequence  1/(k+QUE)^ESS
    (define inv-pow (vector-map