
(FPCore (x y z t) :precision binary64 (- (* x x) (* (* y 4.0) (- (* z z) t))))
double code(double x, double y, double z, double t) {
return (x * x) - ((y * 4.0) * ((z * z) - t));
}
module fmin_fmax_functions
implicit none
private
public fmax
public fmin
interface fmax
module procedure fmax88
module procedure fmax44
module procedure fmax84
module procedure fmax48
end interface
interface fmin
module procedure fmin88
module procedure fmin44
module procedure fmin84
module procedure fmin48
end interface
contains
real(8) function fmax88(x, y) result (res)
real(8), intent (in) :: x
real(8), intent (in) :: y
res = merge(y, merge(x, max(x, y), y /= y), x /= x)
end function
real(4) function fmax44(x, y) result (res)
real(4), intent (in) :: x
real(4), intent (in) :: y
res = merge(y, merge(x, max(x, y), y /= y), x /= x)
end function
real(8) function fmax84(x, y) result(res)
real(8), intent (in) :: x
real(4), intent (in) :: y
res = merge(dble(y), merge(x, max(x, dble(y)), y /= y), x /= x)
end function
real(8) function fmax48(x, y) result(res)
real(4), intent (in) :: x
real(8), intent (in) :: y
res = merge(y, merge(dble(x), max(dble(x), y), y /= y), x /= x)
end function
real(8) function fmin88(x, y) result (res)
real(8), intent (in) :: x
real(8), intent (in) :: y
res = merge(y, merge(x, min(x, y), y /= y), x /= x)
end function
real(4) function fmin44(x, y) result (res)
real(4), intent (in) :: x
real(4), intent (in) :: y
res = merge(y, merge(x, min(x, y), y /= y), x /= x)
end function
real(8) function fmin84(x, y) result(res)
real(8), intent (in) :: x
real(4), intent (in) :: y
res = merge(dble(y), merge(x, min(x, dble(y)), y /= y), x /= x)
end function
real(8) function fmin48(x, y) result(res)
real(4), intent (in) :: x
real(8), intent (in) :: y
res = merge(y, merge(dble(x), min(dble(x), y), y /= y), x /= x)
end function
end module
real(8) function code(x, y, z, t)
use fmin_fmax_functions
real(8), intent (in) :: x
real(8), intent (in) :: y
real(8), intent (in) :: z
real(8), intent (in) :: t
code = (x * x) - ((y * 4.0d0) * ((z * z) - t))
end function
public static double code(double x, double y, double z, double t) {
return (x * x) - ((y * 4.0) * ((z * z) - t));
}
def code(x, y, z, t): return (x * x) - ((y * 4.0) * ((z * z) - t))
function code(x, y, z, t) return Float64(Float64(x * x) - Float64(Float64(y * 4.0) * Float64(Float64(z * z) - t))) end
function tmp = code(x, y, z, t) tmp = (x * x) - ((y * 4.0) * ((z * z) - t)); end
code[x_, y_, z_, t_] := N[(N[(x * x), $MachinePrecision] - N[(N[(y * 4.0), $MachinePrecision] * N[(N[(z * z), $MachinePrecision] - t), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}
\\
x \cdot x - \left(y \cdot 4\right) \cdot \left(z \cdot z - t\right)
\end{array}
Sampling outcomes in binary64 precision:
Herbie found 6 alternatives:
| Alternative | Accuracy | Speedup |
|---|
(FPCore (x y z t) :precision binary64 (- (* x x) (* (* y 4.0) (- (* z z) t))))
double code(double x, double y, double z, double t) {
return (x * x) - ((y * 4.0) * ((z * z) - t));
}
module fmin_fmax_functions
implicit none
private
public fmax
public fmin
interface fmax
module procedure fmax88
module procedure fmax44
module procedure fmax84
module procedure fmax48
end interface
interface fmin
module procedure fmin88
module procedure fmin44
module procedure fmin84
module procedure fmin48
end interface
contains
real(8) function fmax88(x, y) result (res)
real(8), intent (in) :: x
real(8), intent (in) :: y
res = merge(y, merge(x, max(x, y), y /= y), x /= x)
end function
real(4) function fmax44(x, y) result (res)
real(4), intent (in) :: x
real(4), intent (in) :: y
res = merge(y, merge(x, max(x, y), y /= y), x /= x)
end function
real(8) function fmax84(x, y) result(res)
real(8), intent (in) :: x
real(4), intent (in) :: y
res = merge(dble(y), merge(x, max(x, dble(y)), y /= y), x /= x)
end function
real(8) function fmax48(x, y) result(res)
real(4), intent (in) :: x
real(8), intent (in) :: y
res = merge(y, merge(dble(x), max(dble(x), y), y /= y), x /= x)
end function
real(8) function fmin88(x, y) result (res)
real(8), intent (in) :: x
real(8), intent (in) :: y
res = merge(y, merge(x, min(x, y), y /= y), x /= x)
end function
real(4) function fmin44(x, y) result (res)
real(4), intent (in) :: x
real(4), intent (in) :: y
res = merge(y, merge(x, min(x, y), y /= y), x /= x)
end function
real(8) function fmin84(x, y) result(res)
real(8), intent (in) :: x
real(4), intent (in) :: y
res = merge(dble(y), merge(x, min(x, dble(y)), y /= y), x /= x)
end function
real(8) function fmin48(x, y) result(res)
real(4), intent (in) :: x
real(8), intent (in) :: y
res = merge(y, merge(dble(x), min(dble(x), y), y /= y), x /= x)
end function
end module
real(8) function code(x, y, z, t)
use fmin_fmax_functions
real(8), intent (in) :: x
real(8), intent (in) :: y
real(8), intent (in) :: z
real(8), intent (in) :: t
code = (x * x) - ((y * 4.0d0) * ((z * z) - t))
end function
public static double code(double x, double y, double z, double t) {
return (x * x) - ((y * 4.0) * ((z * z) - t));
}
def code(x, y, z, t): return (x * x) - ((y * 4.0) * ((z * z) - t))
function code(x, y, z, t) return Float64(Float64(x * x) - Float64(Float64(y * 4.0) * Float64(Float64(z * z) - t))) end
function tmp = code(x, y, z, t) tmp = (x * x) - ((y * 4.0) * ((z * z) - t)); end
code[x_, y_, z_, t_] := N[(N[(x * x), $MachinePrecision] - N[(N[(y * 4.0), $MachinePrecision] * N[(N[(z * z), $MachinePrecision] - t), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}
\\
x \cdot x - \left(y \cdot 4\right) \cdot \left(z \cdot z - t\right)
\end{array}
(FPCore (x y z t) :precision binary64 (fma (- x) (- x) (* (fma y t (* (* (- y) z) z)) 4.0)))
double code(double x, double y, double z, double t) {
return fma(-x, -x, (fma(y, t, ((-y * z) * z)) * 4.0));
}
function code(x, y, z, t) return fma(Float64(-x), Float64(-x), Float64(fma(y, t, Float64(Float64(Float64(-y) * z) * z)) * 4.0)) end
code[x_, y_, z_, t_] := N[((-x) * (-x) + N[(N[(y * t + N[(N[((-y) * z), $MachinePrecision] * z), $MachinePrecision]), $MachinePrecision] * 4.0), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}
\\
\mathsf{fma}\left(-x, -x, \mathsf{fma}\left(y, t, \left(\left(-y\right) \cdot z\right) \cdot z\right) \cdot 4\right)
\end{array}
Initial program 92.0%
lift--.f64N/A
lift-*.f64N/A
pow2N/A
lift-*.f64N/A
lift-*.f64N/A
lift--.f64N/A
lift-*.f64N/A
*-commutativeN/A
pow2N/A
associate-*r*N/A
*-commutativeN/A
fp-cancel-sub-sign-invN/A
*-rgt-identityN/A
pow2N/A
sqr-neg-revN/A
metadata-evalN/A
unswap-sqrN/A
lower-fma.f64N/A
Applied rewrites93.9%
lift-neg.f64N/A
lift-*.f64N/A
lift-neg.f64N/A
lift-fma.f64N/A
pow2N/A
distribute-lft-inN/A
mul-1-negN/A
associate-*r*N/A
+-commutativeN/A
mul-1-negN/A
mul-1-negN/A
associate-*r*N/A
mul-1-negN/A
lower-fma.f64N/A
mul-1-negN/A
lower-*.f64N/A
mul-1-negN/A
lift-neg.f64N/A
associate-*r*N/A
pow2N/A
associate-*r*N/A
lower-*.f64N/A
Applied rewrites98.8%
Final simplification98.8%
(FPCore (x y z t) :precision binary64 (fma (- x) (- x) (* (* y (fma z z (- t))) (- 4.0))))
double code(double x, double y, double z, double t) {
return fma(-x, -x, ((y * fma(z, z, -t)) * -4.0));
}
function code(x, y, z, t) return fma(Float64(-x), Float64(-x), Float64(Float64(y * fma(z, z, Float64(-t))) * Float64(-4.0))) end
code[x_, y_, z_, t_] := N[((-x) * (-x) + N[(N[(y * N[(z * z + (-t)), $MachinePrecision]), $MachinePrecision] * (-4.0)), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}
\\
\mathsf{fma}\left(-x, -x, \left(y \cdot \mathsf{fma}\left(z, z, -t\right)\right) \cdot \left(-4\right)\right)
\end{array}
Initial program 92.0%
lift--.f64N/A
lift-*.f64N/A
pow2N/A
lift-*.f64N/A
lift-*.f64N/A
lift--.f64N/A
lift-*.f64N/A
*-commutativeN/A
pow2N/A
associate-*r*N/A
*-commutativeN/A
fp-cancel-sub-sign-invN/A
*-rgt-identityN/A
pow2N/A
sqr-neg-revN/A
metadata-evalN/A
unswap-sqrN/A
lower-fma.f64N/A
Applied rewrites93.9%
Final simplification93.9%
(FPCore (x y z t)
:precision binary64
(let* ((t_1 (- (* x x) (* (* y 4.0) (- (* z z) t)))))
(if (<= t_1 INFINITY)
t_1
(*
(/ (fma (* (/ (* -4.0 y) x) (fma z z (- t))) 2.0 (* x 2.0)) (* x 2.0))
(* x x)))))
double code(double x, double y, double z, double t) {
double t_1 = (x * x) - ((y * 4.0) * ((z * z) - t));
double tmp;
if (t_1 <= ((double) INFINITY)) {
tmp = t_1;
} else {
tmp = (fma((((-4.0 * y) / x) * fma(z, z, -t)), 2.0, (x * 2.0)) / (x * 2.0)) * (x * x);
}
return tmp;
}
function code(x, y, z, t) t_1 = Float64(Float64(x * x) - Float64(Float64(y * 4.0) * Float64(Float64(z * z) - t))) tmp = 0.0 if (t_1 <= Inf) tmp = t_1; else tmp = Float64(Float64(fma(Float64(Float64(Float64(-4.0 * y) / x) * fma(z, z, Float64(-t))), 2.0, Float64(x * 2.0)) / Float64(x * 2.0)) * Float64(x * x)); end return tmp end
code[x_, y_, z_, t_] := Block[{t$95$1 = N[(N[(x * x), $MachinePrecision] - N[(N[(y * 4.0), $MachinePrecision] * N[(N[(z * z), $MachinePrecision] - t), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]}, If[LessEqual[t$95$1, Infinity], t$95$1, N[(N[(N[(N[(N[(N[(-4.0 * y), $MachinePrecision] / x), $MachinePrecision] * N[(z * z + (-t)), $MachinePrecision]), $MachinePrecision] * 2.0 + N[(x * 2.0), $MachinePrecision]), $MachinePrecision] / N[(x * 2.0), $MachinePrecision]), $MachinePrecision] * N[(x * x), $MachinePrecision]), $MachinePrecision]]]
\begin{array}{l}
\\
\begin{array}{l}
t_1 := x \cdot x - \left(y \cdot 4\right) \cdot \left(z \cdot z - t\right)\\
\mathbf{if}\;t\_1 \leq \infty:\\
\;\;\;\;t\_1\\
\mathbf{else}:\\
\;\;\;\;\frac{\mathsf{fma}\left(\frac{-4 \cdot y}{x} \cdot \mathsf{fma}\left(z, z, -t\right), 2, x \cdot 2\right)}{x \cdot 2} \cdot \left(x \cdot x\right)\\
\end{array}
\end{array}
if (-.f64 (*.f64 x x) (*.f64 (*.f64 y #s(literal 4 binary64)) (-.f64 (*.f64 z z) t))) < +inf.0Initial program 95.3%
if +inf.0 < (-.f64 (*.f64 x x) (*.f64 (*.f64 y #s(literal 4 binary64)) (-.f64 (*.f64 z z) t))) Initial program 0.0%
lift--.f64N/A
lift-*.f64N/A
pow2N/A
lift-*.f64N/A
lift-*.f64N/A
lift--.f64N/A
lift-*.f64N/A
*-commutativeN/A
pow2N/A
associate-*r*N/A
*-commutativeN/A
fp-cancel-sub-sign-invN/A
*-rgt-identityN/A
pow2N/A
sqr-neg-revN/A
metadata-evalN/A
unswap-sqrN/A
lower-fma.f64N/A
Applied rewrites55.6%
Taylor expanded in x around inf
*-commutativeN/A
lower-*.f64N/A
Applied rewrites77.8%
lift-fma.f64N/A
lift-*.f64N/A
lift-/.f64N/A
lift-/.f64N/A
lift-neg.f64N/A
lift-fma.f64N/A
associate-*r/N/A
metadata-evalN/A
frac-addN/A
lower-/.f64N/A
Applied rewrites77.8%
(FPCore (x y z t)
:precision binary64
(if (<= (* x x) 5e-306)
(- (* x x) (* (* y 4.0) (- t)))
(*
(/ (fma (* (/ (* -4.0 y) x) (fma z z (- t))) 2.0 (* x 2.0)) (* x 2.0))
(* x x))))
double code(double x, double y, double z, double t) {
double tmp;
if ((x * x) <= 5e-306) {
tmp = (x * x) - ((y * 4.0) * -t);
} else {
tmp = (fma((((-4.0 * y) / x) * fma(z, z, -t)), 2.0, (x * 2.0)) / (x * 2.0)) * (x * x);
}
return tmp;
}
function code(x, y, z, t) tmp = 0.0 if (Float64(x * x) <= 5e-306) tmp = Float64(Float64(x * x) - Float64(Float64(y * 4.0) * Float64(-t))); else tmp = Float64(Float64(fma(Float64(Float64(Float64(-4.0 * y) / x) * fma(z, z, Float64(-t))), 2.0, Float64(x * 2.0)) / Float64(x * 2.0)) * Float64(x * x)); end return tmp end
code[x_, y_, z_, t_] := If[LessEqual[N[(x * x), $MachinePrecision], 5e-306], N[(N[(x * x), $MachinePrecision] - N[(N[(y * 4.0), $MachinePrecision] * (-t)), $MachinePrecision]), $MachinePrecision], N[(N[(N[(N[(N[(N[(-4.0 * y), $MachinePrecision] / x), $MachinePrecision] * N[(z * z + (-t)), $MachinePrecision]), $MachinePrecision] * 2.0 + N[(x * 2.0), $MachinePrecision]), $MachinePrecision] / N[(x * 2.0), $MachinePrecision]), $MachinePrecision] * N[(x * x), $MachinePrecision]), $MachinePrecision]]
\begin{array}{l}
\\
\begin{array}{l}
\mathbf{if}\;x \cdot x \leq 5 \cdot 10^{-306}:\\
\;\;\;\;x \cdot x - \left(y \cdot 4\right) \cdot \left(-t\right)\\
\mathbf{else}:\\
\;\;\;\;\frac{\mathsf{fma}\left(\frac{-4 \cdot y}{x} \cdot \mathsf{fma}\left(z, z, -t\right), 2, x \cdot 2\right)}{x \cdot 2} \cdot \left(x \cdot x\right)\\
\end{array}
\end{array}
if (*.f64 x x) < 4.99999999999999998e-306Initial program 95.2%
Taylor expanded in z around 0
mul-1-negN/A
lower-neg.f6463.3
Applied rewrites63.3%
if 4.99999999999999998e-306 < (*.f64 x x) Initial program 91.0%
lift--.f64N/A
lift-*.f64N/A
pow2N/A
lift-*.f64N/A
lift-*.f64N/A
lift--.f64N/A
lift-*.f64N/A
*-commutativeN/A
pow2N/A
associate-*r*N/A
*-commutativeN/A
fp-cancel-sub-sign-invN/A
*-rgt-identityN/A
pow2N/A
sqr-neg-revN/A
metadata-evalN/A
unswap-sqrN/A
lower-fma.f64N/A
Applied rewrites93.6%
Taylor expanded in x around inf
*-commutativeN/A
lower-*.f64N/A
Applied rewrites87.8%
lift-fma.f64N/A
lift-*.f64N/A
lift-/.f64N/A
lift-/.f64N/A
lift-neg.f64N/A
lift-fma.f64N/A
associate-*r/N/A
metadata-evalN/A
frac-addN/A
lower-/.f64N/A
Applied rewrites88.2%
(FPCore (x y z t)
:precision binary64
(let* ((t_1 (/ (* -4.0 y) x)))
(if (<= (* x x) 5e-306)
(* (fma (* (- x) x) (/ (fma t_1 (/ (* z z) x) 1.0) t) (* -4.0 y)) (- t))
(* (/ (fma (* t_1 (fma z z (- t))) 2.0 (* x 2.0)) (* x 2.0)) (* x x)))))
double code(double x, double y, double z, double t) {
double t_1 = (-4.0 * y) / x;
double tmp;
if ((x * x) <= 5e-306) {
tmp = fma((-x * x), (fma(t_1, ((z * z) / x), 1.0) / t), (-4.0 * y)) * -t;
} else {
tmp = (fma((t_1 * fma(z, z, -t)), 2.0, (x * 2.0)) / (x * 2.0)) * (x * x);
}
return tmp;
}
function code(x, y, z, t) t_1 = Float64(Float64(-4.0 * y) / x) tmp = 0.0 if (Float64(x * x) <= 5e-306) tmp = Float64(fma(Float64(Float64(-x) * x), Float64(fma(t_1, Float64(Float64(z * z) / x), 1.0) / t), Float64(-4.0 * y)) * Float64(-t)); else tmp = Float64(Float64(fma(Float64(t_1 * fma(z, z, Float64(-t))), 2.0, Float64(x * 2.0)) / Float64(x * 2.0)) * Float64(x * x)); end return tmp end
code[x_, y_, z_, t_] := Block[{t$95$1 = N[(N[(-4.0 * y), $MachinePrecision] / x), $MachinePrecision]}, If[LessEqual[N[(x * x), $MachinePrecision], 5e-306], N[(N[(N[((-x) * x), $MachinePrecision] * N[(N[(t$95$1 * N[(N[(z * z), $MachinePrecision] / x), $MachinePrecision] + 1.0), $MachinePrecision] / t), $MachinePrecision] + N[(-4.0 * y), $MachinePrecision]), $MachinePrecision] * (-t)), $MachinePrecision], N[(N[(N[(N[(t$95$1 * N[(z * z + (-t)), $MachinePrecision]), $MachinePrecision] * 2.0 + N[(x * 2.0), $MachinePrecision]), $MachinePrecision] / N[(x * 2.0), $MachinePrecision]), $MachinePrecision] * N[(x * x), $MachinePrecision]), $MachinePrecision]]]
\begin{array}{l}
\\
\begin{array}{l}
t_1 := \frac{-4 \cdot y}{x}\\
\mathbf{if}\;x \cdot x \leq 5 \cdot 10^{-306}:\\
\;\;\;\;\mathsf{fma}\left(\left(-x\right) \cdot x, \frac{\mathsf{fma}\left(t\_1, \frac{z \cdot z}{x}, 1\right)}{t}, -4 \cdot y\right) \cdot \left(-t\right)\\
\mathbf{else}:\\
\;\;\;\;\frac{\mathsf{fma}\left(t\_1 \cdot \mathsf{fma}\left(z, z, -t\right), 2, x \cdot 2\right)}{x \cdot 2} \cdot \left(x \cdot x\right)\\
\end{array}
\end{array}
if (*.f64 x x) < 4.99999999999999998e-306Initial program 95.2%
lift--.f64N/A
lift-*.f64N/A
pow2N/A
lift-*.f64N/A
lift-*.f64N/A
lift--.f64N/A
lift-*.f64N/A
*-commutativeN/A
pow2N/A
associate-*r*N/A
*-commutativeN/A
fp-cancel-sub-sign-invN/A
*-rgt-identityN/A
pow2N/A
sqr-neg-revN/A
metadata-evalN/A
unswap-sqrN/A
lower-fma.f64N/A
Applied rewrites95.2%
Taylor expanded in x around inf
*-commutativeN/A
lower-*.f64N/A
Applied rewrites4.2%
Taylor expanded in t around -inf
mul-1-negN/A
*-commutativeN/A
distribute-rgt-neg-inN/A
lower-*.f64N/A
Applied rewrites23.0%
if 4.99999999999999998e-306 < (*.f64 x x) Initial program 91.0%
lift--.f64N/A
lift-*.f64N/A
pow2N/A
lift-*.f64N/A
lift-*.f64N/A
lift--.f64N/A
lift-*.f64N/A
*-commutativeN/A
pow2N/A
associate-*r*N/A
*-commutativeN/A
fp-cancel-sub-sign-invN/A
*-rgt-identityN/A
pow2N/A
sqr-neg-revN/A
metadata-evalN/A
unswap-sqrN/A
lower-fma.f64N/A
Applied rewrites93.6%
Taylor expanded in x around inf
*-commutativeN/A
lower-*.f64N/A
Applied rewrites87.8%
lift-fma.f64N/A
lift-*.f64N/A
lift-/.f64N/A
lift-/.f64N/A
lift-neg.f64N/A
lift-fma.f64N/A
associate-*r/N/A
metadata-evalN/A
frac-addN/A
lower-/.f64N/A
Applied rewrites88.2%
(FPCore (x y z t) :precision binary64 (* (fma (* (- x) x) (/ (fma (/ (* -4.0 y) x) (/ (* z z) x) 1.0) t) (* -4.0 y)) (- t)))
double code(double x, double y, double z, double t) {
return fma((-x * x), (fma(((-4.0 * y) / x), ((z * z) / x), 1.0) / t), (-4.0 * y)) * -t;
}
function code(x, y, z, t) return Float64(fma(Float64(Float64(-x) * x), Float64(fma(Float64(Float64(-4.0 * y) / x), Float64(Float64(z * z) / x), 1.0) / t), Float64(-4.0 * y)) * Float64(-t)) end
code[x_, y_, z_, t_] := N[(N[(N[((-x) * x), $MachinePrecision] * N[(N[(N[(N[(-4.0 * y), $MachinePrecision] / x), $MachinePrecision] * N[(N[(z * z), $MachinePrecision] / x), $MachinePrecision] + 1.0), $MachinePrecision] / t), $MachinePrecision] + N[(-4.0 * y), $MachinePrecision]), $MachinePrecision] * (-t)), $MachinePrecision]
\begin{array}{l}
\\
\mathsf{fma}\left(\left(-x\right) \cdot x, \frac{\mathsf{fma}\left(\frac{-4 \cdot y}{x}, \frac{z \cdot z}{x}, 1\right)}{t}, -4 \cdot y\right) \cdot \left(-t\right)
\end{array}
Initial program 92.0%
lift--.f64N/A
lift-*.f64N/A
pow2N/A
lift-*.f64N/A
lift-*.f64N/A
lift--.f64N/A
lift-*.f64N/A
*-commutativeN/A
pow2N/A
associate-*r*N/A
*-commutativeN/A
fp-cancel-sub-sign-invN/A
*-rgt-identityN/A
pow2N/A
sqr-neg-revN/A
metadata-evalN/A
unswap-sqrN/A
lower-fma.f64N/A
Applied rewrites93.9%
Taylor expanded in x around inf
*-commutativeN/A
lower-*.f64N/A
Applied rewrites67.8%
Taylor expanded in t around -inf
mul-1-negN/A
*-commutativeN/A
distribute-rgt-neg-inN/A
lower-*.f64N/A
Applied rewrites64.8%
herbie shell --seed 2025059
(FPCore (x y z t)
:name "Graphics.Rasterific.Shading:$sradialGradientWithFocusShader from Rasterific-0.6.1, B"
:precision binary64
:alt
(! :herbie-platform default (- (* x x) (* 4 (* y (- (* z z) t)))))
(- (* x x) (* (* y 4.0) (- (* z z) t))))