Average Error: 18.3 → 8.1
Time: 9.3s
Precision: binary64
\[\left(\left(-2 \cdot J\right) \cdot \cos \left(\frac{K}{2}\right)\right) \cdot \sqrt{1 + {\left(\frac{U}{\left(2 \cdot J\right) \cdot \cos \left(\frac{K}{2}\right)}\right)}^{2}} \]
↓
\[\begin{array}{l} t_0 := J \cdot \cos \left(\frac{K}{2}\right)\\ t_1 := -2 \cdot \left(t_0 \cdot \mathsf{hypot}\left(1, \frac{U}{2 \cdot t_0}\right)\right)\\ \mathbf{if}\;J \leq -4.641535401497652 \cdot 10^{-284}:\\ \;\;\;\;t_1\\ \mathbf{elif}\;J \leq 1.2647836566049889 \cdot 10^{-250}:\\ \;\;\;\;-2 \cdot \mathsf{fma}\left(0.5, U, \frac{J}{\frac{U}{J}} \cdot {\cos \left(K \cdot 0.5\right)}^{2}\right)\\ \mathbf{else}:\\ \;\;\;\;t_1\\ \end{array} \]
(FPCore (J K U)
 :precision binary64
 (*
  (* (* -2.0 J) (cos (/ K 2.0)))
  (sqrt (+ 1.0 (pow (/ U (* (* 2.0 J) (cos (/ K 2.0)))) 2.0)))))
↓
(FPCore (J K U)
 :precision binary64
 (let* ((t_0 (* J (cos (/ K 2.0))))
        (t_1 (* -2.0 (* t_0 (hypot 1.0 (/ U (* 2.0 t_0)))))))
   (if (<= J -4.641535401497652e-284)
     t_1
     (if (<= J 1.2647836566049889e-250)
       (* -2.0 (fma 0.5 U (* (/ J (/ U J)) (pow (cos (* K 0.5)) 2.0))))
       t_1))))
double code(double J, double K, double U) {
	return ((-2.0 * J) * cos((K / 2.0))) * sqrt((1.0 + pow((U / ((2.0 * J) * cos((K / 2.0)))), 2.0)));
}
↓
double code(double J, double K, double U) {
	double t_0 = J * cos((K / 2.0));
	double t_1 = -2.0 * (t_0 * hypot(1.0, (U / (2.0 * t_0))));
	double tmp;
	if (J <= -4.641535401497652e-284) {
		tmp = t_1;
	} else if (J <= 1.2647836566049889e-250) {
		tmp = -2.0 * fma(0.5, U, ((J / (U / J)) * pow(cos((K * 0.5)), 2.0)));
	} else {
		tmp = t_1;
	}
	return tmp;
}

function code(J, K, U)
	return Float64(Float64(Float64(-2.0 * J) * cos(Float64(K / 2.0))) * sqrt(Float64(1.0 + (Float64(U / Float64(Float64(2.0 * J) * cos(Float64(K / 2.0)))) ^ 2.0))))
end
↓
function code(J, K, U)
	t_0 = Float64(J * cos(Float64(K / 2.0)))
	t_1 = Float64(-2.0 * Float64(t_0 * hypot(1.0, Float64(U / Float64(2.0 * t_0)))))
	tmp = 0.0
	if (J <= -4.641535401497652e-284)
		tmp = t_1;
	elseif (J <= 1.2647836566049889e-250)
		tmp = Float64(-2.0 * fma(0.5, U, Float64(Float64(J / Float64(U / J)) * (cos(Float64(K * 0.5)) ^ 2.0))));
	else
		tmp = t_1;
	end
	return tmp
end

code[J_, K_, U_] := N[(N[(N[(-2.0 * J), $MachinePrecision] * N[Cos[N[(K / 2.0), $MachinePrecision]], $MachinePrecision]), $MachinePrecision] * N[Sqrt[N[(1.0 + N[Power[N[(U / N[(N[(2.0 * J), $MachinePrecision] * N[Cos[N[(K / 2.0), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]), $MachinePrecision], 2.0], $MachinePrecision]), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]
↓
code[J_, K_, U_] := Block[{t$95$0 = N[(J * N[Cos[N[(K / 2.0), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]}, Block[{t$95$1 = N[(-2.0 * N[(t$95$0 * N[Sqrt[1.0 ^ 2 + N[(U / N[(2.0 * t$95$0), $MachinePrecision]), $MachinePrecision] ^ 2], $MachinePrecision]), $MachinePrecision]), $MachinePrecision]}, If[LessEqual[J, -4.641535401497652e-284], t$95$1, If[LessEqual[J, 1.2647836566049889e-250], N[(-2.0 * N[(0.5 * U + N[(N[(J / N[(U / J), $MachinePrecision]), $MachinePrecision] * N[Power[N[Cos[N[(K * 0.5), $MachinePrecision]], $MachinePrecision], 2.0], $MachinePrecision]), $MachinePrecision]), $MachinePrecision]), $MachinePrecision], t$95$1]]]]

\left(\left(-2 \cdot J\right) \cdot \cos \left(\frac{K}{2}\right)\right) \cdot \sqrt{1 + {\left(\frac{U}{\left(2 \cdot J\right) \cdot \cos \left(\frac{K}{2}\right)}\right)}^{2}}
↓
\begin{array}{l}
t_0 := J \cdot \cos \left(\frac{K}{2}\right)\\
t_1 := -2 \cdot \left(t_0 \cdot \mathsf{hypot}\left(1, \frac{U}{2 \cdot t_0}\right)\right)\\
\mathbf{if}\;J \leq -4.641535401497652 \cdot 10^{-284}:\\
\;\;\;\;t_1\\

\mathbf{elif}\;J \leq 1.2647836566049889 \cdot 10^{-250}:\\
\;\;\;\;-2 \cdot \mathsf{fma}\left(0.5, U, \frac{J}{\frac{U}{J}} \cdot {\cos \left(K \cdot 0.5\right)}^{2}\right)\\

\mathbf{else}:\\
\;\;\;\;t_1\\


\end{array}

Error

Derivation

  1. Split input into 2 regimes

  2. if J < -4.64153540149765195e-284 or 1.26478365660498888e-250 < J

    1. Initial program 16.3

      \[\left(\left(-2 \cdot J\right) \cdot \cos \left(\frac{K}{2}\right)\right) \cdot \sqrt{1 + {\left(\frac{U}{\left(2 \cdot J\right) \cdot \cos \left(\frac{K}{2}\right)}\right)}^{2}} \]

    2. Simplified6.4

      \[\leadsto \color{blue}{-2 \cdot \left(\mathsf{hypot}\left(1, \frac{U}{2 \cdot \left(J \cdot \cos \left(\frac{K}{2}\right)\right)}\right) \cdot \left(J \cdot \cos \left(\frac{K}{2}\right)\right)\right)} \]

    if -4.64153540149765195e-284 < J < 1.26478365660498888e-250

    1. Initial program 47.1

      \[\left(\left(-2 \cdot J\right) \cdot \cos \left(\frac{K}{2}\right)\right) \cdot \sqrt{1 + {\left(\frac{U}{\left(2 \cdot J\right) \cdot \cos \left(\frac{K}{2}\right)}\right)}^{2}} \]

    2. Simplified32.4

      \[\leadsto \color{blue}{-2 \cdot \left(\mathsf{hypot}\left(1, \frac{U}{2 \cdot \left(J \cdot \cos \left(\frac{K}{2}\right)\right)}\right) \cdot \left(J \cdot \cos \left(\frac{K}{2}\right)\right)\right)} \]

    3. Applied egg-rr32.5

      \[\leadsto -2 \cdot \color{blue}{\left(0 + J \cdot \left(\cos \left(K \cdot 0.5\right) \cdot \mathsf{hypot}\left(1, \frac{U}{\cos \left(K \cdot 0.5\right) \cdot \left(2 \cdot J\right)}\right)\right)\right)} \]

    4. Applied egg-rr32.5

      \[\leadsto -2 \cdot \left(0 + J \cdot \left(\cos \left(K \cdot 0.5\right) \cdot \mathsf{hypot}\left(1, \color{blue}{U \cdot \frac{\frac{1}{J + J}}{\cos \left(K \cdot 0.5\right)}}\right)\right)\right) \]

    5. Taylor expanded in J around 0 33.0

      \[\leadsto -2 \cdot \left(0 + \color{blue}{\left(0.5 \cdot U + \frac{{\cos \left(0.5 \cdot K\right)}^{2} \cdot {J}^{2}}{U}\right)}\right) \]

    6. Simplified32.9

      \[\leadsto -2 \cdot \left(0 + \color{blue}{\mathsf{fma}\left(0.5, U, \frac{J}{\frac{U}{J}} \cdot {\cos \left(0.5 \cdot K\right)}^{2}\right)}\right) \]
  3. Recombined 2 regimes into one program.

  4. Final simplification8.1

    \[\leadsto \begin{array}{l} \mathbf{if}\;J \leq -4.641535401497652 \cdot 10^{-284}:\\ \;\;\;\;-2 \cdot \left(\left(J \cdot \cos \left(\frac{K}{2}\right)\right) \cdot \mathsf{hypot}\left(1, \frac{U}{2 \cdot \left(J \cdot \cos \left(\frac{K}{2}\right)\right)}\right)\right)\\ \mathbf{elif}\;J \leq 1.2647836566049889 \cdot 10^{-250}:\\ \;\;\;\;-2 \cdot \mathsf{fma}\left(0.5, U, \frac{J}{\frac{U}{J}} \cdot {\cos \left(K \cdot 0.5\right)}^{2}\right)\\ \mathbf{else}:\\ \;\;\;\;-2 \cdot \left(\left(J \cdot \cos \left(\frac{K}{2}\right)\right) \cdot \mathsf{hypot}\left(1, \frac{U}{2 \cdot \left(J \cdot \cos \left(\frac{K}{2}\right)\right)}\right)\right)\\ \end{array} \]

Reproduce

herbie shell --seed 2022210 
(FPCore (J K U)
  :name "Maksimov and Kolovsky, Equation (3)"
  :precision binary64
  (* (* (* -2.0 J) (cos (/ K 2.0))) (sqrt (+ 1.0 (pow (/ U (* (* 2.0 J) (cos (/ K 2.0)))) 2.0)))))