UniformSampleCone, z

Average Error: 0.11% → 0.06%

Time: 4.0s

Precision: binary32

Cost: 224

\[\left(\left(2.328306437 \cdot 10^{-10} \leq ux \land ux \leq 1\right) \land \left(2.328306437 \cdot 10^{-10} \leq uy \land uy \leq 1\right)\right) \land \left(0 \leq maxCos \land maxCos \leq 1\right)\]

Math

\[\left(1 - ux\right) + ux \cdot maxCos \]

↓

\[1 + ux \cdot \left(maxCos + -1\right) \]

FPCore

(FPCore (ux uy maxCos) :precision binary32 (+ (- 1.0 ux) (* ux maxCos)))

↓

(FPCore (ux uy maxCos) :precision binary32 (+ 1.0 (* ux (+ maxCos -1.0))))

C

float code(float ux, float uy, float maxCos) {
	return (1.0f - ux) + (ux * maxCos);
}

↓

float code(float ux, float uy, float maxCos) {
	return 1.0f + (ux * (maxCos + -1.0f));
}

Fortran

real(4) function code(ux, uy, maxcos)
    real(4), intent (in) :: ux
    real(4), intent (in) :: uy
    real(4), intent (in) :: maxcos
    code = (1.0e0 - ux) + (ux * maxcos)
end function

↓

real(4) function code(ux, uy, maxcos)
    real(4), intent (in) :: ux
    real(4), intent (in) :: uy
    real(4), intent (in) :: maxcos
    code = 1.0e0 + (ux * (maxcos + (-1.0e0)))
end function

Julia

function code(ux, uy, maxCos)
	return Float32(Float32(Float32(1.0) - ux) + Float32(ux * maxCos))
end

↓

function code(ux, uy, maxCos)
	return Float32(Float32(1.0) + Float32(ux * Float32(maxCos + Float32(-1.0))))
end

MATLAB

function tmp = code(ux, uy, maxCos)
	tmp = (single(1.0) - ux) + (ux * maxCos);
end

↓

function tmp = code(ux, uy, maxCos)
	tmp = single(1.0) + (ux * (maxCos + single(-1.0)));
end

Derivation

1. Initial program 0.11

   \[\left(1 - ux\right) + ux \cdot maxCos \]

2. Applied egg-rr 0.06

   \[\leadsto \color{blue}{1 - ux \cdot \left(1 - maxCos\right)} \]

3. Final simplification 0.06

   \[\leadsto 1 + ux \cdot \left(maxCos + -1\right) \]

Alternatives

Alternative 1
Error	0.11%
Cost	224

\[\left(1 - ux\right) + ux \cdot maxCos \]

Alternative 2
Error	1.82%
Cost	96

\[1 - ux \]

Alternative 3
Error	28.63%
Cost	32

\[1 \]

Reproduce

herbie shell --seed 2023089 
(FPCore (ux uy maxCos)
  :name "UniformSampleCone, z"
  :precision binary32
  :pre (and (and (and (<= 2.328306437e-10 ux) (<= ux 1.0)) (and (<= 2.328306437e-10 uy) (<= uy 1.0))) (and (<= 0.0 maxCos) (<= maxCos 1.0)))
  (+ (- 1.0 ux) (* ux maxCos)))