f2dc2027f6
in the original GitHub fork: https://github.com/ntoronto/racket Some things about this are known to be broken (most egregious is that the array tests DO NOT RUN because of a problem in typed/rackunit), about half has no coverage in the tests, and half has no documentation. Fixes and docs are coming. This is committed now to allow others to find errors and inconsistency in the things that appear to be working, and to give the author a (rather incomplete) sense of closure.
190 lines
6.3 KiB
Racket
190 lines
6.3 KiB
Racket
#lang typed/racket/base
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(require racket/performance-hint
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"flonum-functions.rkt"
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"flonum-constants.rkt"
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"flonum-exp.rkt"
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"flonum-log.rkt"
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"flonum-syntax.rkt")
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(provide flsqrt1pm1
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flsinh flcosh fltanh
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flasinh flacosh flatanh
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make-flexp/base flexpt+ flexpt1p)
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;; ---------------------------------------------------------------------------------------------------
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;; sqrt(1+x)-1
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(: flsqrt1pm1 (Float -> Float))
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(define (flsqrt1pm1 x)
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(cond [((flabs x) . fl> . 0.75)
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(fl- (flsqrt (fl+ 1.0 x)) 1.0)]
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[else
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(flexpm1 (fl* 0.5 (fllog1p x)))]))
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;; ---------------------------------------------------------------------------------------------------
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;; Hyperbolic sine
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(: flsinh (Float -> Float))
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(define (flsinh x)
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(cond [(x . fl< . 0.0)
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;; Odd function
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(- (flsinh (- x)))]
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[(x . fl< . (flexpt 2.0 -26.0))
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;; sinh(x) ~ x
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x]
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[(x . fl< . 18.5)
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;; sinh(x) = (exp(2*x) - 1) / (2*exp(x))
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(define y (flexpm1 x))
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(fl* 0.5 (fl+ y (fl/ y (fl+ y 1.0))))]
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[(x . fl< . (fllog +max.0))
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;; sinh(x) ~ exp(x) / 2
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(fl* 0.5 (flexp x))]
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[else
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;; sinh(x) ~ exp(x) / 2 = (exp(x/2) / 2) * exp(x/2)
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(define y (flexp (fl* 0.5 x)))
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(fl* (fl* 0.5 y) y)]))
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;; ---------------------------------------------------------------------------------------------------
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;; Hyperbolic cosine
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(: flcosh (Float -> Float))
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(define (flcosh x)
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;; cosh(x) = cosh(-x)
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(let ([x (flabs x)])
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(cond [(x . fl< . (flexpt 2.0 -26.0))
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;; cosh(x) ~ 1
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1.0]
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[(x . fl< . (fl* 0.5 (fllog 2.0)))
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;; cosh(x) = 1 + (exp(x) - 1)^2 / (2*exp(x))
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(define y (flexpm1 x))
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(fl+ 1.0 (fl/ (fl* y y) (fl* 2.0 (fl+ 1.0 y))))]
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[(x . fl< . 18.5)
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;; cosh(x) = (exp(x) + 1/exp(x)) / 2
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(define y (flexp x))
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(fl+ (fl* 0.5 y) (fl/ 0.5 y))]
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[(x . fl< . (fllog +max.0))
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;; cosh(x) ~ exp(x) / 2
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(fl* 0.5 (flexp x))]
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[else
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;; cosh(x) ~ exp(x) / 2 = (exp(x/2) / 2) * exp(x/2)
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(define y (flexp (fl* 0.5 x)))
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(fl* (fl* 0.5 y) y)])))
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;; ---------------------------------------------------------------------------------------------------
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;; Hyperbolic tangent
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(: fltanh (Float -> Float))
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(define (fltanh x)
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(cond [(x . fl< . 0.0)
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;; tanh(x) = -tanh(-x)
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(- (fltanh (- x)))]
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[(x . fl< . 1e-16)
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;; tanh(x) ~ x + x^2
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(fl* x (fl+ 1.0 x))]
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[(x . fl< . 0.5)
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;; tanh(x) = (exp(2*x) - 1) / (exp(2*x) + 1)
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(define y (flexpm1 (fl* -2.0 x)))
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(- (fl/ y (fl+ 2.0 y)))]
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[(x . fl< . 19.5)
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;; tanh(x) = (exp(2*x) - 1) / (exp(2*x) + 1)
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(define y (flexp (fl* 2.0 x)))
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(fl/ (fl- y 1.0) (fl+ y 1.0))]
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[(x . fl<= . +inf.0)
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;; tanh(x) ~ 1
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1.0]
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[else +nan.0]))
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;; ---------------------------------------------------------------------------------------------------
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;; Inverse hyperbolic sine
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(: flasinh (Float -> Float))
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(define (flasinh x)
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(cond [(x . fl< . 0.0) (- (flasinh (- x)))]
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[(x . fl< . 2e-8) x]
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[(x . fl< . 0.00018)
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;; Taylor series order 3
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(fl* x (fl+ 1.0 (fl* (fl* #i-1/6 x) x)))]
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[(x . fl< . 1.0)
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;; Standard definition, rearranged to preserve digits
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(fllog1p (fl+ x (flsqrt1pm1 (fl* x x))))]
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[(x . fl< . 3e3)
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;; Standard definition
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(fllog (fl+ x (flsqrt (fl+ (fl* x x) 1.0))))]
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[(x . fl< . 1e307)
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;; Laurent series in 1/x at 0+ order from -1 to 1
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(fl+ (fllog (fl* x 2.0)) (fl/ 1.0 (fl* (fl* 4.0 x) x)))]
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[else
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;; Laurent series, rearranged to not overflow
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(fl+ (fllog x) (fllog 2.0))]))
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;; ---------------------------------------------------------------------------------------------------
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;; Inverse hyperbolic cosine
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(: flacosh (Float -> Float))
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(define (flacosh x)
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(cond [(x . fl< . 1.0) +nan.0]
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[(x . fl< . 1.5)
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;; Standard definition, rearranged to preserve digits when x is near 1.0
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(define y (fl- x 1.0))
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(fllog1p (fl+ y (flsqrt (fl+ (fl* y y) (fl* 2.0 y)))))]
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[(x . fl< . 1e8)
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;; Standard definition
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(fllog (fl+ x (flsqrt (fl- (fl* x x) 1.0))))]
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[(x . fl< . 1e307)
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;; Laurent series in 1/x at 0+ order from -1 to 0
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(fllog (fl* x 2.0))]
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[else
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;; Laurent series, rearranged to avoid overflow
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(fl+ (fllog x) (fllog 2.0))]))
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;; ---------------------------------------------------------------------------------------------------
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;; Inverse hyperbolic tangent
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(: flatanh (Float -> Float))
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(define (flatanh x)
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(cond [(x . fl< . 0.0) (- (flatanh (- x)))]
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[(x . fl< . 1e-8) x]
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[(x . fl< . 0.00015)
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;; Taylor series order 2
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(fl+ x (fl* (fl* (fl* #i1/3 x) x) x))]
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[(x . fl< . 0.5)
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;; Standard definition, rearranged to preserve digits when x is near 0.0
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(fl* 0.5 (fl- (fllog1p x) (fllog1p (- x))))]
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[(x . fl< . 1.0)
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;; Standard definition
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(fl* 0.5 (fllog (fl/ (fl+ 1.0 x) (fl- 1.0 x))))]
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[(x . fl= . 1.0) +inf.0]
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[else +nan.0]))
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;; ---------------------------------------------------------------------------------------------------
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;; Exponential with high-precision bases
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(begin-encourage-inline
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(: make-flexp/base (Positive-Exact-Rational -> (Flonum -> Flonum)))
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(define (make-flexp/base b)
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(define b-hi (fl b))
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(define b-lo (fl (- (/ (inexact->exact b-hi) b) 1)))
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(cond [(fl= b-lo 0.0) (λ: ([x : Flonum]) (flexpt b-hi x))]
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[else
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(λ: ([x : Flonum])
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(fl/ (flexpt b-hi x)
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(flexp (fl* x (fllog1p b-lo)))))]))
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(: flexpt+ (Flonum Flonum Flonum -> Flonum))
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(define (flexpt+ a b y)
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(define-values (x-hi x-lo) (fast-fl+/error a b))
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(fl/ (flexpt x-hi y)
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(flexp (fl* y (fllog1p (- (/ x-lo x-hi)))))))
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(: flexpt1p (Flonum Flonum -> Flonum))
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(define (flexpt1p x y)
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(cond [(and (x . > . -0.5) (x . < . +inf.0))
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(define-values (a-hi a-lo) (fast-fl+/error 1.0 x))
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(fl/ (flexpt a-hi y)
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(flexp (fl* y (fllog1p (- (/ a-lo a-hi))))))]
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[else (flexpt (+ 1.0 x) y)]))
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) ; begin-encourage-inline
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