
(FPCore (a1 a2 b1 b2) :precision binary64 (/ (* a1 a2) (* b1 b2)))
double code(double a1, double a2, double b1, double b2) {
return (a1 * a2) / (b1 * b2);
}
real(8) function code(a1, a2, b1, b2)
real(8), intent (in) :: a1
real(8), intent (in) :: a2
real(8), intent (in) :: b1
real(8), intent (in) :: b2
code = (a1 * a2) / (b1 * b2)
end function
public static double code(double a1, double a2, double b1, double b2) {
return (a1 * a2) / (b1 * b2);
}
def code(a1, a2, b1, b2): return (a1 * a2) / (b1 * b2)
function code(a1, a2, b1, b2) return Float64(Float64(a1 * a2) / Float64(b1 * b2)) end
function tmp = code(a1, a2, b1, b2) tmp = (a1 * a2) / (b1 * b2); end
code[a1_, a2_, b1_, b2_] := N[(N[(a1 * a2), $MachinePrecision] / N[(b1 * b2), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}
\\
\frac{a1 \cdot a2}{b1 \cdot b2}
\end{array}
Sampling outcomes in binary64 precision:
Herbie found 6 alternatives:
| Alternative | Accuracy | Speedup |
|---|
(FPCore (a1 a2 b1 b2) :precision binary64 (/ (* a1 a2) (* b1 b2)))
double code(double a1, double a2, double b1, double b2) {
return (a1 * a2) / (b1 * b2);
}
real(8) function code(a1, a2, b1, b2)
real(8), intent (in) :: a1
real(8), intent (in) :: a2
real(8), intent (in) :: b1
real(8), intent (in) :: b2
code = (a1 * a2) / (b1 * b2)
end function
public static double code(double a1, double a2, double b1, double b2) {
return (a1 * a2) / (b1 * b2);
}
def code(a1, a2, b1, b2): return (a1 * a2) / (b1 * b2)
function code(a1, a2, b1, b2) return Float64(Float64(a1 * a2) / Float64(b1 * b2)) end
function tmp = code(a1, a2, b1, b2) tmp = (a1 * a2) / (b1 * b2); end
code[a1_, a2_, b1_, b2_] := N[(N[(a1 * a2), $MachinePrecision] / N[(b1 * b2), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}
\\
\frac{a1 \cdot a2}{b1 \cdot b2}
\end{array}
(FPCore (a1 a2 b1 b2)
:precision binary64
(let* ((t_0 (/ (* a1 a2) (* b1 b2))))
(if (<= t_0 (- INFINITY))
(/ (/ a2 b2) (/ b1 a1))
(if (<= t_0 -1e-315)
t_0
(if (<= t_0 0.0)
(/ (/ a1 b1) (/ b2 a2))
(if (<= t_0 5e+285) t_0 (* (/ a2 b2) (/ a1 b1))))))))
double code(double a1, double a2, double b1, double b2) {
double t_0 = (a1 * a2) / (b1 * b2);
double tmp;
if (t_0 <= -((double) INFINITY)) {
tmp = (a2 / b2) / (b1 / a1);
} else if (t_0 <= -1e-315) {
tmp = t_0;
} else if (t_0 <= 0.0) {
tmp = (a1 / b1) / (b2 / a2);
} else if (t_0 <= 5e+285) {
tmp = t_0;
} else {
tmp = (a2 / b2) * (a1 / b1);
}
return tmp;
}
public static double code(double a1, double a2, double b1, double b2) {
double t_0 = (a1 * a2) / (b1 * b2);
double tmp;
if (t_0 <= -Double.POSITIVE_INFINITY) {
tmp = (a2 / b2) / (b1 / a1);
} else if (t_0 <= -1e-315) {
tmp = t_0;
} else if (t_0 <= 0.0) {
tmp = (a1 / b1) / (b2 / a2);
} else if (t_0 <= 5e+285) {
tmp = t_0;
} else {
tmp = (a2 / b2) * (a1 / b1);
}
return tmp;
}
def code(a1, a2, b1, b2): t_0 = (a1 * a2) / (b1 * b2) tmp = 0 if t_0 <= -math.inf: tmp = (a2 / b2) / (b1 / a1) elif t_0 <= -1e-315: tmp = t_0 elif t_0 <= 0.0: tmp = (a1 / b1) / (b2 / a2) elif t_0 <= 5e+285: tmp = t_0 else: tmp = (a2 / b2) * (a1 / b1) return tmp
function code(a1, a2, b1, b2) t_0 = Float64(Float64(a1 * a2) / Float64(b1 * b2)) tmp = 0.0 if (t_0 <= Float64(-Inf)) tmp = Float64(Float64(a2 / b2) / Float64(b1 / a1)); elseif (t_0 <= -1e-315) tmp = t_0; elseif (t_0 <= 0.0) tmp = Float64(Float64(a1 / b1) / Float64(b2 / a2)); elseif (t_0 <= 5e+285) tmp = t_0; else tmp = Float64(Float64(a2 / b2) * Float64(a1 / b1)); end return tmp end
function tmp_2 = code(a1, a2, b1, b2) t_0 = (a1 * a2) / (b1 * b2); tmp = 0.0; if (t_0 <= -Inf) tmp = (a2 / b2) / (b1 / a1); elseif (t_0 <= -1e-315) tmp = t_0; elseif (t_0 <= 0.0) tmp = (a1 / b1) / (b2 / a2); elseif (t_0 <= 5e+285) tmp = t_0; else tmp = (a2 / b2) * (a1 / b1); end tmp_2 = tmp; end
code[a1_, a2_, b1_, b2_] := Block[{t$95$0 = N[(N[(a1 * a2), $MachinePrecision] / N[(b1 * b2), $MachinePrecision]), $MachinePrecision]}, If[LessEqual[t$95$0, (-Infinity)], N[(N[(a2 / b2), $MachinePrecision] / N[(b1 / a1), $MachinePrecision]), $MachinePrecision], If[LessEqual[t$95$0, -1e-315], t$95$0, If[LessEqual[t$95$0, 0.0], N[(N[(a1 / b1), $MachinePrecision] / N[(b2 / a2), $MachinePrecision]), $MachinePrecision], If[LessEqual[t$95$0, 5e+285], t$95$0, N[(N[(a2 / b2), $MachinePrecision] * N[(a1 / b1), $MachinePrecision]), $MachinePrecision]]]]]]
\begin{array}{l}
\\
\begin{array}{l}
t_0 := \frac{a1 \cdot a2}{b1 \cdot b2}\\
\mathbf{if}\;t_0 \leq -\infty:\\
\;\;\;\;\frac{\frac{a2}{b2}}{\frac{b1}{a1}}\\
\mathbf{elif}\;t_0 \leq -1 \cdot 10^{-315}:\\
\;\;\;\;t_0\\
\mathbf{elif}\;t_0 \leq 0:\\
\;\;\;\;\frac{\frac{a1}{b1}}{\frac{b2}{a2}}\\
\mathbf{elif}\;t_0 \leq 5 \cdot 10^{+285}:\\
\;\;\;\;t_0\\
\mathbf{else}:\\
\;\;\;\;\frac{a2}{b2} \cdot \frac{a1}{b1}\\
\end{array}
\end{array}
if (/.f64 (*.f64 a1 a2) (*.f64 b1 b2)) < -inf.0Initial program 80.6%
times-frac99.9%
*-commutative99.9%
Simplified99.9%
clear-num99.9%
un-div-inv99.9%
Applied egg-rr99.9%
if -inf.0 < (/.f64 (*.f64 a1 a2) (*.f64 b1 b2)) < -9.999999985e-316 or 0.0 < (/.f64 (*.f64 a1 a2) (*.f64 b1 b2)) < 5.00000000000000016e285Initial program 99.4%
if -9.999999985e-316 < (/.f64 (*.f64 a1 a2) (*.f64 b1 b2)) < 0.0Initial program 84.1%
times-frac98.7%
*-commutative98.7%
Simplified98.7%
*-commutative98.7%
clear-num98.7%
un-div-inv98.8%
Applied egg-rr98.8%
if 5.00000000000000016e285 < (/.f64 (*.f64 a1 a2) (*.f64 b1 b2)) Initial program 69.5%
times-frac95.4%
*-commutative95.4%
Simplified95.4%
Final simplification98.6%
(FPCore (a1 a2 b1 b2)
:precision binary64
(let* ((t_0 (/ (* a1 a2) (* b1 b2))))
(if (or (<= t_0 (- INFINITY))
(and (not (<= t_0 -1e-315))
(or (<= t_0 0.0) (not (<= t_0 5e+285)))))
(* (/ a2 b2) (/ a1 b1))
t_0)))
double code(double a1, double a2, double b1, double b2) {
double t_0 = (a1 * a2) / (b1 * b2);
double tmp;
if ((t_0 <= -((double) INFINITY)) || (!(t_0 <= -1e-315) && ((t_0 <= 0.0) || !(t_0 <= 5e+285)))) {
tmp = (a2 / b2) * (a1 / b1);
} else {
tmp = t_0;
}
return tmp;
}
public static double code(double a1, double a2, double b1, double b2) {
double t_0 = (a1 * a2) / (b1 * b2);
double tmp;
if ((t_0 <= -Double.POSITIVE_INFINITY) || (!(t_0 <= -1e-315) && ((t_0 <= 0.0) || !(t_0 <= 5e+285)))) {
tmp = (a2 / b2) * (a1 / b1);
} else {
tmp = t_0;
}
return tmp;
}
def code(a1, a2, b1, b2): t_0 = (a1 * a2) / (b1 * b2) tmp = 0 if (t_0 <= -math.inf) or (not (t_0 <= -1e-315) and ((t_0 <= 0.0) or not (t_0 <= 5e+285))): tmp = (a2 / b2) * (a1 / b1) else: tmp = t_0 return tmp
function code(a1, a2, b1, b2) t_0 = Float64(Float64(a1 * a2) / Float64(b1 * b2)) tmp = 0.0 if ((t_0 <= Float64(-Inf)) || (!(t_0 <= -1e-315) && ((t_0 <= 0.0) || !(t_0 <= 5e+285)))) tmp = Float64(Float64(a2 / b2) * Float64(a1 / b1)); else tmp = t_0; end return tmp end
function tmp_2 = code(a1, a2, b1, b2) t_0 = (a1 * a2) / (b1 * b2); tmp = 0.0; if ((t_0 <= -Inf) || (~((t_0 <= -1e-315)) && ((t_0 <= 0.0) || ~((t_0 <= 5e+285))))) tmp = (a2 / b2) * (a1 / b1); else tmp = t_0; end tmp_2 = tmp; end
code[a1_, a2_, b1_, b2_] := Block[{t$95$0 = N[(N[(a1 * a2), $MachinePrecision] / N[(b1 * b2), $MachinePrecision]), $MachinePrecision]}, If[Or[LessEqual[t$95$0, (-Infinity)], And[N[Not[LessEqual[t$95$0, -1e-315]], $MachinePrecision], Or[LessEqual[t$95$0, 0.0], N[Not[LessEqual[t$95$0, 5e+285]], $MachinePrecision]]]], N[(N[(a2 / b2), $MachinePrecision] * N[(a1 / b1), $MachinePrecision]), $MachinePrecision], t$95$0]]
\begin{array}{l}
\\
\begin{array}{l}
t_0 := \frac{a1 \cdot a2}{b1 \cdot b2}\\
\mathbf{if}\;t_0 \leq -\infty \lor \neg \left(t_0 \leq -1 \cdot 10^{-315}\right) \land \left(t_0 \leq 0 \lor \neg \left(t_0 \leq 5 \cdot 10^{+285}\right)\right):\\
\;\;\;\;\frac{a2}{b2} \cdot \frac{a1}{b1}\\
\mathbf{else}:\\
\;\;\;\;t_0\\
\end{array}
\end{array}
if (/.f64 (*.f64 a1 a2) (*.f64 b1 b2)) < -inf.0 or -9.999999985e-316 < (/.f64 (*.f64 a1 a2) (*.f64 b1 b2)) < 0.0 or 5.00000000000000016e285 < (/.f64 (*.f64 a1 a2) (*.f64 b1 b2)) Initial program 79.3%
times-frac98.0%
*-commutative98.0%
Simplified98.0%
if -inf.0 < (/.f64 (*.f64 a1 a2) (*.f64 b1 b2)) < -9.999999985e-316 or 0.0 < (/.f64 (*.f64 a1 a2) (*.f64 b1 b2)) < 5.00000000000000016e285Initial program 99.4%
Final simplification98.6%
(FPCore (a1 a2 b1 b2)
:precision binary64
(let* ((t_0 (/ (* a1 a2) (* b1 b2))) (t_1 (* (/ a2 b2) (/ a1 b1))))
(if (<= t_0 (- INFINITY))
t_1
(if (<= t_0 -1e-315)
t_0
(if (<= t_0 0.0)
(/ (/ a1 b1) (/ b2 a2))
(if (<= t_0 5e+285) t_0 t_1))))))
double code(double a1, double a2, double b1, double b2) {
double t_0 = (a1 * a2) / (b1 * b2);
double t_1 = (a2 / b2) * (a1 / b1);
double tmp;
if (t_0 <= -((double) INFINITY)) {
tmp = t_1;
} else if (t_0 <= -1e-315) {
tmp = t_0;
} else if (t_0 <= 0.0) {
tmp = (a1 / b1) / (b2 / a2);
} else if (t_0 <= 5e+285) {
tmp = t_0;
} else {
tmp = t_1;
}
return tmp;
}
public static double code(double a1, double a2, double b1, double b2) {
double t_0 = (a1 * a2) / (b1 * b2);
double t_1 = (a2 / b2) * (a1 / b1);
double tmp;
if (t_0 <= -Double.POSITIVE_INFINITY) {
tmp = t_1;
} else if (t_0 <= -1e-315) {
tmp = t_0;
} else if (t_0 <= 0.0) {
tmp = (a1 / b1) / (b2 / a2);
} else if (t_0 <= 5e+285) {
tmp = t_0;
} else {
tmp = t_1;
}
return tmp;
}
def code(a1, a2, b1, b2): t_0 = (a1 * a2) / (b1 * b2) t_1 = (a2 / b2) * (a1 / b1) tmp = 0 if t_0 <= -math.inf: tmp = t_1 elif t_0 <= -1e-315: tmp = t_0 elif t_0 <= 0.0: tmp = (a1 / b1) / (b2 / a2) elif t_0 <= 5e+285: tmp = t_0 else: tmp = t_1 return tmp
function code(a1, a2, b1, b2) t_0 = Float64(Float64(a1 * a2) / Float64(b1 * b2)) t_1 = Float64(Float64(a2 / b2) * Float64(a1 / b1)) tmp = 0.0 if (t_0 <= Float64(-Inf)) tmp = t_1; elseif (t_0 <= -1e-315) tmp = t_0; elseif (t_0 <= 0.0) tmp = Float64(Float64(a1 / b1) / Float64(b2 / a2)); elseif (t_0 <= 5e+285) tmp = t_0; else tmp = t_1; end return tmp end
function tmp_2 = code(a1, a2, b1, b2) t_0 = (a1 * a2) / (b1 * b2); t_1 = (a2 / b2) * (a1 / b1); tmp = 0.0; if (t_0 <= -Inf) tmp = t_1; elseif (t_0 <= -1e-315) tmp = t_0; elseif (t_0 <= 0.0) tmp = (a1 / b1) / (b2 / a2); elseif (t_0 <= 5e+285) tmp = t_0; else tmp = t_1; end tmp_2 = tmp; end
code[a1_, a2_, b1_, b2_] := Block[{t$95$0 = N[(N[(a1 * a2), $MachinePrecision] / N[(b1 * b2), $MachinePrecision]), $MachinePrecision]}, Block[{t$95$1 = N[(N[(a2 / b2), $MachinePrecision] * N[(a1 / b1), $MachinePrecision]), $MachinePrecision]}, If[LessEqual[t$95$0, (-Infinity)], t$95$1, If[LessEqual[t$95$0, -1e-315], t$95$0, If[LessEqual[t$95$0, 0.0], N[(N[(a1 / b1), $MachinePrecision] / N[(b2 / a2), $MachinePrecision]), $MachinePrecision], If[LessEqual[t$95$0, 5e+285], t$95$0, t$95$1]]]]]]
\begin{array}{l}
\\
\begin{array}{l}
t_0 := \frac{a1 \cdot a2}{b1 \cdot b2}\\
t_1 := \frac{a2}{b2} \cdot \frac{a1}{b1}\\
\mathbf{if}\;t_0 \leq -\infty:\\
\;\;\;\;t_1\\
\mathbf{elif}\;t_0 \leq -1 \cdot 10^{-315}:\\
\;\;\;\;t_0\\
\mathbf{elif}\;t_0 \leq 0:\\
\;\;\;\;\frac{\frac{a1}{b1}}{\frac{b2}{a2}}\\
\mathbf{elif}\;t_0 \leq 5 \cdot 10^{+285}:\\
\;\;\;\;t_0\\
\mathbf{else}:\\
\;\;\;\;t_1\\
\end{array}
\end{array}
if (/.f64 (*.f64 a1 a2) (*.f64 b1 b2)) < -inf.0 or 5.00000000000000016e285 < (/.f64 (*.f64 a1 a2) (*.f64 b1 b2)) Initial program 74.1%
times-frac97.3%
*-commutative97.3%
Simplified97.3%
if -inf.0 < (/.f64 (*.f64 a1 a2) (*.f64 b1 b2)) < -9.999999985e-316 or 0.0 < (/.f64 (*.f64 a1 a2) (*.f64 b1 b2)) < 5.00000000000000016e285Initial program 99.4%
if -9.999999985e-316 < (/.f64 (*.f64 a1 a2) (*.f64 b1 b2)) < 0.0Initial program 84.1%
times-frac98.7%
*-commutative98.7%
Simplified98.7%
*-commutative98.7%
clear-num98.7%
un-div-inv98.8%
Applied egg-rr98.8%
Final simplification98.6%
(FPCore (a1 a2 b1 b2) :precision binary64 (if (<= b2 9e-269) (* a2 (/ a1 (* b1 b2))) (* (/ a2 b2) (/ a1 b1))))
double code(double a1, double a2, double b1, double b2) {
double tmp;
if (b2 <= 9e-269) {
tmp = a2 * (a1 / (b1 * b2));
} else {
tmp = (a2 / b2) * (a1 / b1);
}
return tmp;
}
real(8) function code(a1, a2, b1, b2)
real(8), intent (in) :: a1
real(8), intent (in) :: a2
real(8), intent (in) :: b1
real(8), intent (in) :: b2
real(8) :: tmp
if (b2 <= 9d-269) then
tmp = a2 * (a1 / (b1 * b2))
else
tmp = (a2 / b2) * (a1 / b1)
end if
code = tmp
end function
public static double code(double a1, double a2, double b1, double b2) {
double tmp;
if (b2 <= 9e-269) {
tmp = a2 * (a1 / (b1 * b2));
} else {
tmp = (a2 / b2) * (a1 / b1);
}
return tmp;
}
def code(a1, a2, b1, b2): tmp = 0 if b2 <= 9e-269: tmp = a2 * (a1 / (b1 * b2)) else: tmp = (a2 / b2) * (a1 / b1) return tmp
function code(a1, a2, b1, b2) tmp = 0.0 if (b2 <= 9e-269) tmp = Float64(a2 * Float64(a1 / Float64(b1 * b2))); else tmp = Float64(Float64(a2 / b2) * Float64(a1 / b1)); end return tmp end
function tmp_2 = code(a1, a2, b1, b2) tmp = 0.0; if (b2 <= 9e-269) tmp = a2 * (a1 / (b1 * b2)); else tmp = (a2 / b2) * (a1 / b1); end tmp_2 = tmp; end
code[a1_, a2_, b1_, b2_] := If[LessEqual[b2, 9e-269], N[(a2 * N[(a1 / N[(b1 * b2), $MachinePrecision]), $MachinePrecision]), $MachinePrecision], N[(N[(a2 / b2), $MachinePrecision] * N[(a1 / b1), $MachinePrecision]), $MachinePrecision]]
\begin{array}{l}
\\
\begin{array}{l}
\mathbf{if}\;b2 \leq 9 \cdot 10^{-269}:\\
\;\;\;\;a2 \cdot \frac{a1}{b1 \cdot b2}\\
\mathbf{else}:\\
\;\;\;\;\frac{a2}{b2} \cdot \frac{a1}{b1}\\
\end{array}
\end{array}
if b2 < 9.0000000000000003e-269Initial program 93.2%
associate-/l*91.7%
associate-/r/93.0%
*-commutative93.0%
Applied egg-rr93.0%
if 9.0000000000000003e-269 < b2 Initial program 82.5%
times-frac91.5%
*-commutative91.5%
Simplified91.5%
Final simplification92.3%
(FPCore (a1 a2 b1 b2) :precision binary64 (* a1 (/ a2 (* b1 b2))))
double code(double a1, double a2, double b1, double b2) {
return a1 * (a2 / (b1 * b2));
}
real(8) function code(a1, a2, b1, b2)
real(8), intent (in) :: a1
real(8), intent (in) :: a2
real(8), intent (in) :: b1
real(8), intent (in) :: b2
code = a1 * (a2 / (b1 * b2))
end function
public static double code(double a1, double a2, double b1, double b2) {
return a1 * (a2 / (b1 * b2));
}
def code(a1, a2, b1, b2): return a1 * (a2 / (b1 * b2))
function code(a1, a2, b1, b2) return Float64(a1 * Float64(a2 / Float64(b1 * b2))) end
function tmp = code(a1, a2, b1, b2) tmp = a1 * (a2 / (b1 * b2)); end
code[a1_, a2_, b1_, b2_] := N[(a1 * N[(a2 / N[(b1 * b2), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}
\\
a1 \cdot \frac{a2}{b1 \cdot b2}
\end{array}
Initial program 87.9%
times-frac86.5%
*-commutative86.5%
Simplified86.5%
Taylor expanded in a2 around 0 87.9%
*-commutative87.9%
associate-*r/88.8%
*-commutative88.8%
Simplified88.8%
Final simplification88.8%
(FPCore (a1 a2 b1 b2) :precision binary64 (* a2 (/ a1 (* b1 b2))))
double code(double a1, double a2, double b1, double b2) {
return a2 * (a1 / (b1 * b2));
}
real(8) function code(a1, a2, b1, b2)
real(8), intent (in) :: a1
real(8), intent (in) :: a2
real(8), intent (in) :: b1
real(8), intent (in) :: b2
code = a2 * (a1 / (b1 * b2))
end function
public static double code(double a1, double a2, double b1, double b2) {
return a2 * (a1 / (b1 * b2));
}
def code(a1, a2, b1, b2): return a2 * (a1 / (b1 * b2))
function code(a1, a2, b1, b2) return Float64(a2 * Float64(a1 / Float64(b1 * b2))) end
function tmp = code(a1, a2, b1, b2) tmp = a2 * (a1 / (b1 * b2)); end
code[a1_, a2_, b1_, b2_] := N[(a2 * N[(a1 / N[(b1 * b2), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}
\\
a2 \cdot \frac{a1}{b1 \cdot b2}
\end{array}
Initial program 87.9%
associate-/l*88.7%
associate-/r/89.3%
*-commutative89.3%
Applied egg-rr89.3%
Final simplification89.3%
(FPCore (a1 a2 b1 b2) :precision binary64 (* (/ a1 b1) (/ a2 b2)))
double code(double a1, double a2, double b1, double b2) {
return (a1 / b1) * (a2 / b2);
}
real(8) function code(a1, a2, b1, b2)
real(8), intent (in) :: a1
real(8), intent (in) :: a2
real(8), intent (in) :: b1
real(8), intent (in) :: b2
code = (a1 / b1) * (a2 / b2)
end function
public static double code(double a1, double a2, double b1, double b2) {
return (a1 / b1) * (a2 / b2);
}
def code(a1, a2, b1, b2): return (a1 / b1) * (a2 / b2)
function code(a1, a2, b1, b2) return Float64(Float64(a1 / b1) * Float64(a2 / b2)) end
function tmp = code(a1, a2, b1, b2) tmp = (a1 / b1) * (a2 / b2); end
code[a1_, a2_, b1_, b2_] := N[(N[(a1 / b1), $MachinePrecision] * N[(a2 / b2), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}
\\
\frac{a1}{b1} \cdot \frac{a2}{b2}
\end{array}
herbie shell --seed 2023275
(FPCore (a1 a2 b1 b2)
:name "Quotient of products"
:precision binary64
:herbie-target
(* (/ a1 b1) (/ a2 b2))
(/ (* a1 a2) (* b1 b2)))