
(FPCore (x y z t a) :precision binary64 (- x (/ (* y (- z t)) a)))
double code(double x, double y, double z, double t, double a) {
return x - ((y * (z - t)) / a);
}
real(8) function code(x, y, z, t, a)
real(8), intent (in) :: x
real(8), intent (in) :: y
real(8), intent (in) :: z
real(8), intent (in) :: t
real(8), intent (in) :: a
code = x - ((y * (z - t)) / a)
end function
public static double code(double x, double y, double z, double t, double a) {
return x - ((y * (z - t)) / a);
}
def code(x, y, z, t, a): return x - ((y * (z - t)) / a)
function code(x, y, z, t, a) return Float64(x - Float64(Float64(y * Float64(z - t)) / a)) end
function tmp = code(x, y, z, t, a) tmp = x - ((y * (z - t)) / a); end
code[x_, y_, z_, t_, a_] := N[(x - N[(N[(y * N[(z - t), $MachinePrecision]), $MachinePrecision] / a), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}
\\
x - \frac{y \cdot \left(z - t\right)}{a}
\end{array}
Sampling outcomes in binary64 precision:
Herbie found 9 alternatives:
| Alternative | Accuracy | Speedup |
|---|
(FPCore (x y z t a) :precision binary64 (- x (/ (* y (- z t)) a)))
double code(double x, double y, double z, double t, double a) {
return x - ((y * (z - t)) / a);
}
real(8) function code(x, y, z, t, a)
real(8), intent (in) :: x
real(8), intent (in) :: y
real(8), intent (in) :: z
real(8), intent (in) :: t
real(8), intent (in) :: a
code = x - ((y * (z - t)) / a)
end function
public static double code(double x, double y, double z, double t, double a) {
return x - ((y * (z - t)) / a);
}
def code(x, y, z, t, a): return x - ((y * (z - t)) / a)
function code(x, y, z, t, a) return Float64(x - Float64(Float64(y * Float64(z - t)) / a)) end
function tmp = code(x, y, z, t, a) tmp = x - ((y * (z - t)) / a); end
code[x_, y_, z_, t_, a_] := N[(x - N[(N[(y * N[(z - t), $MachinePrecision]), $MachinePrecision] / a), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}
\\
x - \frac{y \cdot \left(z - t\right)}{a}
\end{array}
(FPCore (x y z t a) :precision binary64 (let* ((t_1 (* y (- z t)))) (if (<= t_1 -2e+294) (fma (- t z) (/ y a) x) (- x (/ t_1 a)))))
double code(double x, double y, double z, double t, double a) {
double t_1 = y * (z - t);
double tmp;
if (t_1 <= -2e+294) {
tmp = fma((t - z), (y / a), x);
} else {
tmp = x - (t_1 / a);
}
return tmp;
}
function code(x, y, z, t, a) t_1 = Float64(y * Float64(z - t)) tmp = 0.0 if (t_1 <= -2e+294) tmp = fma(Float64(t - z), Float64(y / a), x); else tmp = Float64(x - Float64(t_1 / a)); end return tmp end
code[x_, y_, z_, t_, a_] := Block[{t$95$1 = N[(y * N[(z - t), $MachinePrecision]), $MachinePrecision]}, If[LessEqual[t$95$1, -2e+294], N[(N[(t - z), $MachinePrecision] * N[(y / a), $MachinePrecision] + x), $MachinePrecision], N[(x - N[(t$95$1 / a), $MachinePrecision]), $MachinePrecision]]]
\begin{array}{l}
\\
\begin{array}{l}
t_1 := y \cdot \left(z - t\right)\\
\mathbf{if}\;t\_1 \leq -2 \cdot 10^{+294}:\\
\;\;\;\;\mathsf{fma}\left(t - z, \frac{y}{a}, x\right)\\
\mathbf{else}:\\
\;\;\;\;x - \frac{t\_1}{a}\\
\end{array}
\end{array}
if (*.f64 y (-.f64 z t)) < -2.00000000000000013e294Initial program 80.3%
Taylor expanded in x around 0
*-lft-identityN/A
fp-cancel-sub-sign-invN/A
metadata-evalN/A
+-commutativeN/A
mul-1-negN/A
*-commutativeN/A
associate-/l*N/A
distribute-lft-neg-inN/A
lower-fma.f64N/A
Applied rewrites99.9%
if -2.00000000000000013e294 < (*.f64 y (-.f64 z t)) Initial program 97.8%
(FPCore (x y z t a)
:precision binary64
(let* ((t_1 (/ (* y (- z t)) a)))
(if (or (<= t_1 -2e+126) (not (<= t_1 2e+112)))
(* (- t z) (/ y a))
(fma (- y) (/ z a) x))))
double code(double x, double y, double z, double t, double a) {
double t_1 = (y * (z - t)) / a;
double tmp;
if ((t_1 <= -2e+126) || !(t_1 <= 2e+112)) {
tmp = (t - z) * (y / a);
} else {
tmp = fma(-y, (z / a), x);
}
return tmp;
}
function code(x, y, z, t, a) t_1 = Float64(Float64(y * Float64(z - t)) / a) tmp = 0.0 if ((t_1 <= -2e+126) || !(t_1 <= 2e+112)) tmp = Float64(Float64(t - z) * Float64(y / a)); else tmp = fma(Float64(-y), Float64(z / a), x); end return tmp end
code[x_, y_, z_, t_, a_] := Block[{t$95$1 = N[(N[(y * N[(z - t), $MachinePrecision]), $MachinePrecision] / a), $MachinePrecision]}, If[Or[LessEqual[t$95$1, -2e+126], N[Not[LessEqual[t$95$1, 2e+112]], $MachinePrecision]], N[(N[(t - z), $MachinePrecision] * N[(y / a), $MachinePrecision]), $MachinePrecision], N[((-y) * N[(z / a), $MachinePrecision] + x), $MachinePrecision]]]
\begin{array}{l}
\\
\begin{array}{l}
t_1 := \frac{y \cdot \left(z - t\right)}{a}\\
\mathbf{if}\;t\_1 \leq -2 \cdot 10^{+126} \lor \neg \left(t\_1 \leq 2 \cdot 10^{+112}\right):\\
\;\;\;\;\left(t - z\right) \cdot \frac{y}{a}\\
\mathbf{else}:\\
\;\;\;\;\mathsf{fma}\left(-y, \frac{z}{a}, x\right)\\
\end{array}
\end{array}
if (/.f64 (*.f64 y (-.f64 z t)) a) < -1.99999999999999985e126 or 1.9999999999999999e112 < (/.f64 (*.f64 y (-.f64 z t)) a) Initial program 92.1%
Taylor expanded in x around 0
mul-1-negN/A
*-commutativeN/A
associate-/l*N/A
distribute-lft-neg-inN/A
lower-*.f64N/A
*-lft-identityN/A
metadata-evalN/A
fp-cancel-sign-sub-invN/A
+-commutativeN/A
distribute-neg-inN/A
mul-1-negN/A
remove-double-negN/A
mul-1-negN/A
*-commutativeN/A
fp-cancel-sign-subN/A
mul-1-negN/A
*-commutativeN/A
associate-*l*N/A
metadata-evalN/A
*-rgt-identityN/A
lower--.f64N/A
lower-/.f6493.3
Applied rewrites93.3%
if -1.99999999999999985e126 < (/.f64 (*.f64 y (-.f64 z t)) a) < 1.9999999999999999e112Initial program 99.0%
Taylor expanded in t around 0
*-lft-identityN/A
metadata-evalN/A
fp-cancel-sign-sub-invN/A
+-commutativeN/A
associate-/l*N/A
associate-*r*N/A
lower-fma.f64N/A
mul-1-negN/A
lower-neg.f64N/A
lower-/.f6484.3
Applied rewrites84.3%
Final simplification89.0%
(FPCore (x y z t a)
:precision binary64
(let* ((t_1 (/ (* y (- z t)) a)))
(if (or (<= t_1 -4e+118) (not (<= t_1 2e+112)))
(* (- t z) (/ y a))
(fma (/ t a) y x))))
double code(double x, double y, double z, double t, double a) {
double t_1 = (y * (z - t)) / a;
double tmp;
if ((t_1 <= -4e+118) || !(t_1 <= 2e+112)) {
tmp = (t - z) * (y / a);
} else {
tmp = fma((t / a), y, x);
}
return tmp;
}
function code(x, y, z, t, a) t_1 = Float64(Float64(y * Float64(z - t)) / a) tmp = 0.0 if ((t_1 <= -4e+118) || !(t_1 <= 2e+112)) tmp = Float64(Float64(t - z) * Float64(y / a)); else tmp = fma(Float64(t / a), y, x); end return tmp end
code[x_, y_, z_, t_, a_] := Block[{t$95$1 = N[(N[(y * N[(z - t), $MachinePrecision]), $MachinePrecision] / a), $MachinePrecision]}, If[Or[LessEqual[t$95$1, -4e+118], N[Not[LessEqual[t$95$1, 2e+112]], $MachinePrecision]], N[(N[(t - z), $MachinePrecision] * N[(y / a), $MachinePrecision]), $MachinePrecision], N[(N[(t / a), $MachinePrecision] * y + x), $MachinePrecision]]]
\begin{array}{l}
\\
\begin{array}{l}
t_1 := \frac{y \cdot \left(z - t\right)}{a}\\
\mathbf{if}\;t\_1 \leq -4 \cdot 10^{+118} \lor \neg \left(t\_1 \leq 2 \cdot 10^{+112}\right):\\
\;\;\;\;\left(t - z\right) \cdot \frac{y}{a}\\
\mathbf{else}:\\
\;\;\;\;\mathsf{fma}\left(\frac{t}{a}, y, x\right)\\
\end{array}
\end{array}
if (/.f64 (*.f64 y (-.f64 z t)) a) < -3.99999999999999987e118 or 1.9999999999999999e112 < (/.f64 (*.f64 y (-.f64 z t)) a) Initial program 92.2%
Taylor expanded in x around 0
mul-1-negN/A
*-commutativeN/A
associate-/l*N/A
distribute-lft-neg-inN/A
lower-*.f64N/A
*-lft-identityN/A
metadata-evalN/A
fp-cancel-sign-sub-invN/A
+-commutativeN/A
distribute-neg-inN/A
mul-1-negN/A
remove-double-negN/A
mul-1-negN/A
*-commutativeN/A
fp-cancel-sign-subN/A
mul-1-negN/A
*-commutativeN/A
associate-*l*N/A
metadata-evalN/A
*-rgt-identityN/A
lower--.f64N/A
lower-/.f6493.4
Applied rewrites93.4%
if -3.99999999999999987e118 < (/.f64 (*.f64 y (-.f64 z t)) a) < 1.9999999999999999e112Initial program 99.0%
Taylor expanded in z around 0
fp-cancel-sub-sign-invN/A
metadata-evalN/A
*-lft-identityN/A
+-commutativeN/A
associate-*l/N/A
lower-fma.f64N/A
lower-/.f6482.1
Applied rewrites82.1%
Final simplification88.0%
(FPCore (x y z t a) :precision binary64 (if (or (<= z -4.4e+148) (not (<= z 7e+187))) (* (- z) (/ y a)) (fma (/ y a) t x)))
double code(double x, double y, double z, double t, double a) {
double tmp;
if ((z <= -4.4e+148) || !(z <= 7e+187)) {
tmp = -z * (y / a);
} else {
tmp = fma((y / a), t, x);
}
return tmp;
}
function code(x, y, z, t, a) tmp = 0.0 if ((z <= -4.4e+148) || !(z <= 7e+187)) tmp = Float64(Float64(-z) * Float64(y / a)); else tmp = fma(Float64(y / a), t, x); end return tmp end
code[x_, y_, z_, t_, a_] := If[Or[LessEqual[z, -4.4e+148], N[Not[LessEqual[z, 7e+187]], $MachinePrecision]], N[((-z) * N[(y / a), $MachinePrecision]), $MachinePrecision], N[(N[(y / a), $MachinePrecision] * t + x), $MachinePrecision]]
\begin{array}{l}
\\
\begin{array}{l}
\mathbf{if}\;z \leq -4.4 \cdot 10^{+148} \lor \neg \left(z \leq 7 \cdot 10^{+187}\right):\\
\;\;\;\;\left(-z\right) \cdot \frac{y}{a}\\
\mathbf{else}:\\
\;\;\;\;\mathsf{fma}\left(\frac{y}{a}, t, x\right)\\
\end{array}
\end{array}
if z < -4.3999999999999998e148 or 6.9999999999999995e187 < z Initial program 95.6%
Taylor expanded in z around inf
mul-1-negN/A
associate-/l*N/A
*-commutativeN/A
distribute-lft-neg-inN/A
lower-*.f64N/A
distribute-neg-fracN/A
lower-/.f64N/A
lower-neg.f6470.7
Applied rewrites70.7%
Applied rewrites77.8%
if -4.3999999999999998e148 < z < 6.9999999999999995e187Initial program 95.4%
Taylor expanded in x around 0
*-lft-identityN/A
fp-cancel-sub-sign-invN/A
metadata-evalN/A
+-commutativeN/A
mul-1-negN/A
*-commutativeN/A
associate-/l*N/A
distribute-lft-neg-inN/A
lower-fma.f64N/A
Applied rewrites95.0%
Taylor expanded in z around 0
fp-cancel-sub-sign-invN/A
metadata-evalN/A
*-lft-identityN/A
+-commutativeN/A
*-commutativeN/A
associate-*l/N/A
lower-fma.f64N/A
lower-/.f6480.9
Applied rewrites80.9%
Final simplification80.1%
(FPCore (x y z t a) :precision binary64 (if (<= z -4.4e+148) (* (- z) (/ y a)) (if (<= z 7e+187) (fma (/ y a) t x) (/ (* (- y) z) a))))
double code(double x, double y, double z, double t, double a) {
double tmp;
if (z <= -4.4e+148) {
tmp = -z * (y / a);
} else if (z <= 7e+187) {
tmp = fma((y / a), t, x);
} else {
tmp = (-y * z) / a;
}
return tmp;
}
function code(x, y, z, t, a) tmp = 0.0 if (z <= -4.4e+148) tmp = Float64(Float64(-z) * Float64(y / a)); elseif (z <= 7e+187) tmp = fma(Float64(y / a), t, x); else tmp = Float64(Float64(Float64(-y) * z) / a); end return tmp end
code[x_, y_, z_, t_, a_] := If[LessEqual[z, -4.4e+148], N[((-z) * N[(y / a), $MachinePrecision]), $MachinePrecision], If[LessEqual[z, 7e+187], N[(N[(y / a), $MachinePrecision] * t + x), $MachinePrecision], N[(N[((-y) * z), $MachinePrecision] / a), $MachinePrecision]]]
\begin{array}{l}
\\
\begin{array}{l}
\mathbf{if}\;z \leq -4.4 \cdot 10^{+148}:\\
\;\;\;\;\left(-z\right) \cdot \frac{y}{a}\\
\mathbf{elif}\;z \leq 7 \cdot 10^{+187}:\\
\;\;\;\;\mathsf{fma}\left(\frac{y}{a}, t, x\right)\\
\mathbf{else}:\\
\;\;\;\;\frac{\left(-y\right) \cdot z}{a}\\
\end{array}
\end{array}
if z < -4.3999999999999998e148Initial program 92.9%
Taylor expanded in z around inf
mul-1-negN/A
associate-/l*N/A
*-commutativeN/A
distribute-lft-neg-inN/A
lower-*.f64N/A
distribute-neg-fracN/A
lower-/.f64N/A
lower-neg.f6466.6
Applied rewrites66.6%
Applied rewrites73.7%
if -4.3999999999999998e148 < z < 6.9999999999999995e187Initial program 95.4%
Taylor expanded in x around 0
*-lft-identityN/A
fp-cancel-sub-sign-invN/A
metadata-evalN/A
+-commutativeN/A
mul-1-negN/A
*-commutativeN/A
associate-/l*N/A
distribute-lft-neg-inN/A
lower-fma.f64N/A
Applied rewrites95.0%
Taylor expanded in z around 0
fp-cancel-sub-sign-invN/A
metadata-evalN/A
*-lft-identityN/A
+-commutativeN/A
*-commutativeN/A
associate-*l/N/A
lower-fma.f64N/A
lower-/.f6480.9
Applied rewrites80.9%
if 6.9999999999999995e187 < z Initial program 99.9%
Taylor expanded in z around inf
mul-1-negN/A
associate-/l*N/A
*-commutativeN/A
distribute-lft-neg-inN/A
lower-*.f64N/A
distribute-neg-fracN/A
lower-/.f64N/A
lower-neg.f6477.0
Applied rewrites77.0%
Applied rewrites88.2%
(FPCore (x y z t a) :precision binary64 (fma (- t z) (/ y a) x))
double code(double x, double y, double z, double t, double a) {
return fma((t - z), (y / a), x);
}
function code(x, y, z, t, a) return fma(Float64(t - z), Float64(y / a), x) end
code[x_, y_, z_, t_, a_] := N[(N[(t - z), $MachinePrecision] * N[(y / a), $MachinePrecision] + x), $MachinePrecision]
\begin{array}{l}
\\
\mathsf{fma}\left(t - z, \frac{y}{a}, x\right)
\end{array}
Initial program 95.4%
Taylor expanded in x around 0
*-lft-identityN/A
fp-cancel-sub-sign-invN/A
metadata-evalN/A
+-commutativeN/A
mul-1-negN/A
*-commutativeN/A
associate-/l*N/A
distribute-lft-neg-inN/A
lower-fma.f64N/A
Applied rewrites95.8%
(FPCore (x y z t a) :precision binary64 (fma (/ y a) t x))
double code(double x, double y, double z, double t, double a) {
return fma((y / a), t, x);
}
function code(x, y, z, t, a) return fma(Float64(y / a), t, x) end
code[x_, y_, z_, t_, a_] := N[(N[(y / a), $MachinePrecision] * t + x), $MachinePrecision]
\begin{array}{l}
\\
\mathsf{fma}\left(\frac{y}{a}, t, x\right)
\end{array}
Initial program 95.4%
Taylor expanded in x around 0
*-lft-identityN/A
fp-cancel-sub-sign-invN/A
metadata-evalN/A
+-commutativeN/A
mul-1-negN/A
*-commutativeN/A
associate-/l*N/A
distribute-lft-neg-inN/A
lower-fma.f64N/A
Applied rewrites95.8%
Taylor expanded in z around 0
fp-cancel-sub-sign-invN/A
metadata-evalN/A
*-lft-identityN/A
+-commutativeN/A
*-commutativeN/A
associate-*l/N/A
lower-fma.f64N/A
lower-/.f6467.5
Applied rewrites67.5%
(FPCore (x y z t a) :precision binary64 (fma (/ t a) y x))
double code(double x, double y, double z, double t, double a) {
return fma((t / a), y, x);
}
function code(x, y, z, t, a) return fma(Float64(t / a), y, x) end
code[x_, y_, z_, t_, a_] := N[(N[(t / a), $MachinePrecision] * y + x), $MachinePrecision]
\begin{array}{l}
\\
\mathsf{fma}\left(\frac{t}{a}, y, x\right)
\end{array}
Initial program 95.4%
Taylor expanded in z around 0
fp-cancel-sub-sign-invN/A
metadata-evalN/A
*-lft-identityN/A
+-commutativeN/A
associate-*l/N/A
lower-fma.f64N/A
lower-/.f6467.0
Applied rewrites67.0%
(FPCore (x y z t a) :precision binary64 (* t (/ y a)))
double code(double x, double y, double z, double t, double a) {
return t * (y / a);
}
real(8) function code(x, y, z, t, a)
real(8), intent (in) :: x
real(8), intent (in) :: y
real(8), intent (in) :: z
real(8), intent (in) :: t
real(8), intent (in) :: a
code = t * (y / a)
end function
public static double code(double x, double y, double z, double t, double a) {
return t * (y / a);
}
def code(x, y, z, t, a): return t * (y / a)
function code(x, y, z, t, a) return Float64(t * Float64(y / a)) end
function tmp = code(x, y, z, t, a) tmp = t * (y / a); end
code[x_, y_, z_, t_, a_] := N[(t * N[(y / a), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}
\\
t \cdot \frac{y}{a}
\end{array}
Initial program 95.4%
Taylor expanded in t around inf
associate-*l/N/A
lower-*.f64N/A
lower-/.f6433.5
Applied rewrites33.5%
Applied rewrites34.1%
(FPCore (x y z t a)
:precision binary64
(let* ((t_1 (/ a (- z t))))
(if (< y -1.0761266216389975e-10)
(- x (/ 1.0 (/ t_1 y)))
(if (< y 2.894426862792089e-49)
(- x (/ (* y (- z t)) a))
(- x (/ y t_1))))))
double code(double x, double y, double z, double t, double a) {
double t_1 = a / (z - t);
double tmp;
if (y < -1.0761266216389975e-10) {
tmp = x - (1.0 / (t_1 / y));
} else if (y < 2.894426862792089e-49) {
tmp = x - ((y * (z - t)) / a);
} else {
tmp = x - (y / t_1);
}
return tmp;
}
real(8) function code(x, y, z, t, a)
real(8), intent (in) :: x
real(8), intent (in) :: y
real(8), intent (in) :: z
real(8), intent (in) :: t
real(8), intent (in) :: a
real(8) :: t_1
real(8) :: tmp
t_1 = a / (z - t)
if (y < (-1.0761266216389975d-10)) then
tmp = x - (1.0d0 / (t_1 / y))
else if (y < 2.894426862792089d-49) then
tmp = x - ((y * (z - t)) / a)
else
tmp = x - (y / t_1)
end if
code = tmp
end function
public static double code(double x, double y, double z, double t, double a) {
double t_1 = a / (z - t);
double tmp;
if (y < -1.0761266216389975e-10) {
tmp = x - (1.0 / (t_1 / y));
} else if (y < 2.894426862792089e-49) {
tmp = x - ((y * (z - t)) / a);
} else {
tmp = x - (y / t_1);
}
return tmp;
}
def code(x, y, z, t, a): t_1 = a / (z - t) tmp = 0 if y < -1.0761266216389975e-10: tmp = x - (1.0 / (t_1 / y)) elif y < 2.894426862792089e-49: tmp = x - ((y * (z - t)) / a) else: tmp = x - (y / t_1) return tmp
function code(x, y, z, t, a) t_1 = Float64(a / Float64(z - t)) tmp = 0.0 if (y < -1.0761266216389975e-10) tmp = Float64(x - Float64(1.0 / Float64(t_1 / y))); elseif (y < 2.894426862792089e-49) tmp = Float64(x - Float64(Float64(y * Float64(z - t)) / a)); else tmp = Float64(x - Float64(y / t_1)); end return tmp end
function tmp_2 = code(x, y, z, t, a) t_1 = a / (z - t); tmp = 0.0; if (y < -1.0761266216389975e-10) tmp = x - (1.0 / (t_1 / y)); elseif (y < 2.894426862792089e-49) tmp = x - ((y * (z - t)) / a); else tmp = x - (y / t_1); end tmp_2 = tmp; end
code[x_, y_, z_, t_, a_] := Block[{t$95$1 = N[(a / N[(z - t), $MachinePrecision]), $MachinePrecision]}, If[Less[y, -1.0761266216389975e-10], N[(x - N[(1.0 / N[(t$95$1 / y), $MachinePrecision]), $MachinePrecision]), $MachinePrecision], If[Less[y, 2.894426862792089e-49], N[(x - N[(N[(y * N[(z - t), $MachinePrecision]), $MachinePrecision] / a), $MachinePrecision]), $MachinePrecision], N[(x - N[(y / t$95$1), $MachinePrecision]), $MachinePrecision]]]]
\begin{array}{l}
\\
\begin{array}{l}
t_1 := \frac{a}{z - t}\\
\mathbf{if}\;y < -1.0761266216389975 \cdot 10^{-10}:\\
\;\;\;\;x - \frac{1}{\frac{t\_1}{y}}\\
\mathbf{elif}\;y < 2.894426862792089 \cdot 10^{-49}:\\
\;\;\;\;x - \frac{y \cdot \left(z - t\right)}{a}\\
\mathbf{else}:\\
\;\;\;\;x - \frac{y}{t\_1}\\
\end{array}
\end{array}
herbie shell --seed 2024338
(FPCore (x y z t a)
:name "Optimisation.CirclePacking:place from circle-packing-0.1.0.4, F"
:precision binary64
:alt
(! :herbie-platform default (if (< y -430450648655599/4000000000000000000000000) (- x (/ 1 (/ (/ a (- z t)) y))) (if (< y 2894426862792089/10000000000000000000000000000000000000000000000000000000000000000) (- x (/ (* y (- z t)) a)) (- x (/ y (/ a (- z t)))))))
(- x (/ (* y (- z t)) a)))