Faster flonums-between

Author: pavpanchekha

math-lib/math/private/flonum/flonum-bits.rkt

@@ -99,11 +99,21 @@
   (: flprev (Flonum -> Flonum))
   (define (flprev x) (flstep x -1))
 
-  (: flonums-between (Flonum Flonum -> Integer))
-  (define (flonums-between x y)
-    (- (flonum->ordinal y) (flonum->ordinal x)))
-  
   )  ; begin-encourage-inline
+
+(: flonum->chunks (-> Flonum (Values Integer Integer)))
+(define (flonum->chunks x)
+  (define neg? (fl< x 0.0))
+  (define ax (flabs x))
+  (if neg?
+      (values (- (flbit-field ax 0 32)) (- (flbit-field ax 32 64)))
+      (values (flbit-field ax 0 32) (flbit-field ax 32 64))))
+
+(: flonums-between (Flonum Flonum -> Integer))
+(define (flonums-between x y)
+  (define-values (xlo xhi) (flonum->chunks x))
+  (define-values (ylo yhi) (flonum->chunks y))
+  (+ (arithmetic-shift (- yhi xhi) 32) (- ylo xlo)))
 
 (: flulp (Flonum -> (U Flonum-Nan Nonnegative-Flonum)))
 (define (flulp x)

math-test/math/tests/flonum-tests.rkt

@@ -144,6 +144,12 @@
   (check-equal? (flulp-error x (flnext x)) 1.0
                 (format "x = ~a" x)))
 
+(for ([_  (in-range 1000)])
+  (define x (ordinal->flonum (random-integer (flonum->ordinal -inf.0) (flonum->ordinal +inf.0))))
+  (define y (ordinal->flonum (random-integer (flonum->ordinal -inf.0) (flonum->ordinal +inf.0))))
+  (check-equal? (flonums-between x y)
+                (- (flonum->ordinal y) (flonum->ordinal x))))
+
 ;; ===================================================================================================
 ;; fllog2