
(FPCore (x y z t) :precision binary64 (- x (/ (log (+ (- 1.0 y) (* y (exp z)))) t)))
double code(double x, double y, double z, double t) {
return x - (log(((1.0 - y) + (y * exp(z)))) / t);
}
real(8) function code(x, y, z, t)
real(8), intent (in) :: x
real(8), intent (in) :: y
real(8), intent (in) :: z
real(8), intent (in) :: t
code = x - (log(((1.0d0 - y) + (y * exp(z)))) / t)
end function
public static double code(double x, double y, double z, double t) {
return x - (Math.log(((1.0 - y) + (y * Math.exp(z)))) / t);
}
def code(x, y, z, t): return x - (math.log(((1.0 - y) + (y * math.exp(z)))) / t)
function code(x, y, z, t) return Float64(x - Float64(log(Float64(Float64(1.0 - y) + Float64(y * exp(z)))) / t)) end
function tmp = code(x, y, z, t) tmp = x - (log(((1.0 - y) + (y * exp(z)))) / t); end
code[x_, y_, z_, t_] := N[(x - N[(N[Log[N[(N[(1.0 - y), $MachinePrecision] + N[(y * N[Exp[z], $MachinePrecision]), $MachinePrecision]), $MachinePrecision]], $MachinePrecision] / t), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}
\\
x - \frac{\log \left(\left(1 - y\right) + y \cdot e^{z}\right)}{t}
\end{array}
Sampling outcomes in binary64 precision:
Herbie found 7 alternatives:
| Alternative | Accuracy | Speedup |
|---|
(FPCore (x y z t) :precision binary64 (- x (/ (log (+ (- 1.0 y) (* y (exp z)))) t)))
double code(double x, double y, double z, double t) {
return x - (log(((1.0 - y) + (y * exp(z)))) / t);
}
real(8) function code(x, y, z, t)
real(8), intent (in) :: x
real(8), intent (in) :: y
real(8), intent (in) :: z
real(8), intent (in) :: t
code = x - (log(((1.0d0 - y) + (y * exp(z)))) / t)
end function
public static double code(double x, double y, double z, double t) {
return x - (Math.log(((1.0 - y) + (y * Math.exp(z)))) / t);
}
def code(x, y, z, t): return x - (math.log(((1.0 - y) + (y * math.exp(z)))) / t)
function code(x, y, z, t) return Float64(x - Float64(log(Float64(Float64(1.0 - y) + Float64(y * exp(z)))) / t)) end
function tmp = code(x, y, z, t) tmp = x - (log(((1.0 - y) + (y * exp(z)))) / t); end
code[x_, y_, z_, t_] := N[(x - N[(N[Log[N[(N[(1.0 - y), $MachinePrecision] + N[(y * N[Exp[z], $MachinePrecision]), $MachinePrecision]), $MachinePrecision]], $MachinePrecision] / t), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}
\\
x - \frac{\log \left(\left(1 - y\right) + y \cdot e^{z}\right)}{t}
\end{array}
(FPCore (x y z t) :precision binary64 (- x (/ (log1p (* y (expm1 z))) t)))
double code(double x, double y, double z, double t) {
return x - (log1p((y * expm1(z))) / t);
}
public static double code(double x, double y, double z, double t) {
return x - (Math.log1p((y * Math.expm1(z))) / t);
}
def code(x, y, z, t): return x - (math.log1p((y * math.expm1(z))) / t)
function code(x, y, z, t) return Float64(x - Float64(log1p(Float64(y * expm1(z))) / t)) end
code[x_, y_, z_, t_] := N[(x - N[(N[Log[1 + N[(y * N[(Exp[z] - 1), $MachinePrecision]), $MachinePrecision]], $MachinePrecision] / t), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}
\\
x - \frac{\mathsf{log1p}\left(y \cdot \mathsf{expm1}\left(z\right)\right)}{t}
\end{array}
Initial program 68.5%
associate-+l-82.1%
sub-neg82.1%
log1p-define86.1%
neg-sub086.1%
associate-+l-86.1%
neg-sub086.1%
+-commutative86.1%
unsub-neg86.1%
*-rgt-identity86.1%
distribute-lft-out--86.1%
expm1-define98.8%
Simplified98.8%
(FPCore (x y z t)
:precision binary64
(if (<= z -9.5e+274)
x
(if (<= z -6.6e+26)
(- x (/ (* y (expm1 z)) t))
(- x (/ (log1p (* y z)) t)))))
double code(double x, double y, double z, double t) {
double tmp;
if (z <= -9.5e+274) {
tmp = x;
} else if (z <= -6.6e+26) {
tmp = x - ((y * expm1(z)) / t);
} else {
tmp = x - (log1p((y * z)) / t);
}
return tmp;
}
public static double code(double x, double y, double z, double t) {
double tmp;
if (z <= -9.5e+274) {
tmp = x;
} else if (z <= -6.6e+26) {
tmp = x - ((y * Math.expm1(z)) / t);
} else {
tmp = x - (Math.log1p((y * z)) / t);
}
return tmp;
}
def code(x, y, z, t): tmp = 0 if z <= -9.5e+274: tmp = x elif z <= -6.6e+26: tmp = x - ((y * math.expm1(z)) / t) else: tmp = x - (math.log1p((y * z)) / t) return tmp
function code(x, y, z, t) tmp = 0.0 if (z <= -9.5e+274) tmp = x; elseif (z <= -6.6e+26) tmp = Float64(x - Float64(Float64(y * expm1(z)) / t)); else tmp = Float64(x - Float64(log1p(Float64(y * z)) / t)); end return tmp end
code[x_, y_, z_, t_] := If[LessEqual[z, -9.5e+274], x, If[LessEqual[z, -6.6e+26], N[(x - N[(N[(y * N[(Exp[z] - 1), $MachinePrecision]), $MachinePrecision] / t), $MachinePrecision]), $MachinePrecision], N[(x - N[(N[Log[1 + N[(y * z), $MachinePrecision]], $MachinePrecision] / t), $MachinePrecision]), $MachinePrecision]]]
\begin{array}{l}
\\
\begin{array}{l}
\mathbf{if}\;z \leq -9.5 \cdot 10^{+274}:\\
\;\;\;\;x\\
\mathbf{elif}\;z \leq -6.6 \cdot 10^{+26}:\\
\;\;\;\;x - \frac{y \cdot \mathsf{expm1}\left(z\right)}{t}\\
\mathbf{else}:\\
\;\;\;\;x - \frac{\mathsf{log1p}\left(y \cdot z\right)}{t}\\
\end{array}
\end{array}
if z < -9.50000000000000031e274Initial program 100.0%
associate-+l-100.0%
sub-neg100.0%
log1p-define100.0%
neg-sub0100.0%
associate-+l-100.0%
neg-sub0100.0%
+-commutative100.0%
unsub-neg100.0%
*-rgt-identity100.0%
distribute-lft-out--100.0%
expm1-define100.0%
Simplified100.0%
Taylor expanded in x around inf 71.6%
if -9.50000000000000031e274 < z < -6.59999999999999987e26Initial program 83.9%
associate-+l-83.9%
sub-neg83.9%
log1p-define99.9%
neg-sub099.9%
associate-+l-99.9%
neg-sub099.9%
+-commutative99.9%
unsub-neg99.9%
*-rgt-identity99.9%
distribute-lft-out--99.9%
expm1-define99.9%
Simplified99.9%
Taylor expanded in y around 0 78.1%
expm1-define78.1%
Simplified78.1%
if -6.59999999999999987e26 < z Initial program 61.4%
associate-+l-80.5%
sub-neg80.5%
log1p-define80.5%
neg-sub080.5%
associate-+l-80.5%
neg-sub080.5%
+-commutative80.5%
unsub-neg80.5%
*-rgt-identity80.5%
distribute-lft-out--80.5%
expm1-define98.4%
Simplified98.4%
clear-num98.4%
associate-/r/98.3%
Applied egg-rr98.3%
Taylor expanded in z around 0 98.4%
Taylor expanded in x around 0 85.3%
log1p-define98.5%
*-rgt-identity98.5%
*-rgt-identity98.5%
Simplified98.5%
(FPCore (x y z t)
:precision binary64
(if (<= z -4e+270)
x
(if (<= z -1.02e+27)
(- x (* y (/ (expm1 z) t)))
(- x (/ (log1p (* y z)) t)))))
double code(double x, double y, double z, double t) {
double tmp;
if (z <= -4e+270) {
tmp = x;
} else if (z <= -1.02e+27) {
tmp = x - (y * (expm1(z) / t));
} else {
tmp = x - (log1p((y * z)) / t);
}
return tmp;
}
public static double code(double x, double y, double z, double t) {
double tmp;
if (z <= -4e+270) {
tmp = x;
} else if (z <= -1.02e+27) {
tmp = x - (y * (Math.expm1(z) / t));
} else {
tmp = x - (Math.log1p((y * z)) / t);
}
return tmp;
}
def code(x, y, z, t): tmp = 0 if z <= -4e+270: tmp = x elif z <= -1.02e+27: tmp = x - (y * (math.expm1(z) / t)) else: tmp = x - (math.log1p((y * z)) / t) return tmp
function code(x, y, z, t) tmp = 0.0 if (z <= -4e+270) tmp = x; elseif (z <= -1.02e+27) tmp = Float64(x - Float64(y * Float64(expm1(z) / t))); else tmp = Float64(x - Float64(log1p(Float64(y * z)) / t)); end return tmp end
code[x_, y_, z_, t_] := If[LessEqual[z, -4e+270], x, If[LessEqual[z, -1.02e+27], N[(x - N[(y * N[(N[(Exp[z] - 1), $MachinePrecision] / t), $MachinePrecision]), $MachinePrecision]), $MachinePrecision], N[(x - N[(N[Log[1 + N[(y * z), $MachinePrecision]], $MachinePrecision] / t), $MachinePrecision]), $MachinePrecision]]]
\begin{array}{l}
\\
\begin{array}{l}
\mathbf{if}\;z \leq -4 \cdot 10^{+270}:\\
\;\;\;\;x\\
\mathbf{elif}\;z \leq -1.02 \cdot 10^{+27}:\\
\;\;\;\;x - y \cdot \frac{\mathsf{expm1}\left(z\right)}{t}\\
\mathbf{else}:\\
\;\;\;\;x - \frac{\mathsf{log1p}\left(y \cdot z\right)}{t}\\
\end{array}
\end{array}
if z < -4.0000000000000002e270Initial program 100.0%
associate-+l-100.0%
sub-neg100.0%
log1p-define100.0%
neg-sub0100.0%
associate-+l-100.0%
neg-sub0100.0%
+-commutative100.0%
unsub-neg100.0%
*-rgt-identity100.0%
distribute-lft-out--100.0%
expm1-define100.0%
Simplified100.0%
Taylor expanded in x around inf 71.6%
if -4.0000000000000002e270 < z < -1.0199999999999999e27Initial program 83.9%
associate-+l-83.9%
sub-neg83.9%
log1p-define99.9%
neg-sub099.9%
associate-+l-99.9%
neg-sub099.9%
+-commutative99.9%
unsub-neg99.9%
*-rgt-identity99.9%
distribute-lft-out--99.9%
expm1-define99.9%
Simplified99.9%
Taylor expanded in y around 0 78.1%
associate-/l*78.0%
expm1-define78.0%
Simplified78.0%
if -1.0199999999999999e27 < z Initial program 61.4%
associate-+l-80.5%
sub-neg80.5%
log1p-define80.5%
neg-sub080.5%
associate-+l-80.5%
neg-sub080.5%
+-commutative80.5%
unsub-neg80.5%
*-rgt-identity80.5%
distribute-lft-out--80.5%
expm1-define98.4%
Simplified98.4%
clear-num98.4%
associate-/r/98.3%
Applied egg-rr98.3%
Taylor expanded in z around 0 98.4%
Taylor expanded in x around 0 85.3%
log1p-define98.5%
*-rgt-identity98.5%
*-rgt-identity98.5%
Simplified98.5%
(FPCore (x y z t) :precision binary64 (if (<= y -1.15e+186) x (- x (* y (/ (expm1 z) t)))))
double code(double x, double y, double z, double t) {
double tmp;
if (y <= -1.15e+186) {
tmp = x;
} else {
tmp = x - (y * (expm1(z) / t));
}
return tmp;
}
public static double code(double x, double y, double z, double t) {
double tmp;
if (y <= -1.15e+186) {
tmp = x;
} else {
tmp = x - (y * (Math.expm1(z) / t));
}
return tmp;
}
def code(x, y, z, t): tmp = 0 if y <= -1.15e+186: tmp = x else: tmp = x - (y * (math.expm1(z) / t)) return tmp
function code(x, y, z, t) tmp = 0.0 if (y <= -1.15e+186) tmp = x; else tmp = Float64(x - Float64(y * Float64(expm1(z) / t))); end return tmp end
code[x_, y_, z_, t_] := If[LessEqual[y, -1.15e+186], x, N[(x - N[(y * N[(N[(Exp[z] - 1), $MachinePrecision] / t), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]]
\begin{array}{l}
\\
\begin{array}{l}
\mathbf{if}\;y \leq -1.15 \cdot 10^{+186}:\\
\;\;\;\;x\\
\mathbf{else}:\\
\;\;\;\;x - y \cdot \frac{\mathsf{expm1}\left(z\right)}{t}\\
\end{array}
\end{array}
if y < -1.15000000000000007e186Initial program 67.3%
associate-+l-90.6%
sub-neg90.6%
log1p-define90.6%
neg-sub090.6%
associate-+l-90.6%
neg-sub090.6%
+-commutative90.6%
unsub-neg90.6%
*-rgt-identity90.6%
distribute-lft-out--90.6%
expm1-define99.9%
Simplified99.9%
Taylor expanded in x around inf 60.3%
if -1.15000000000000007e186 < y Initial program 68.6%
associate-+l-81.3%
sub-neg81.3%
log1p-define85.7%
neg-sub085.7%
associate-+l-85.7%
neg-sub085.7%
+-commutative85.7%
unsub-neg85.7%
*-rgt-identity85.7%
distribute-lft-out--85.7%
expm1-define98.7%
Simplified98.7%
Taylor expanded in y around 0 81.5%
associate-/l*81.4%
expm1-define90.6%
Simplified90.6%
(FPCore (x y z t) :precision binary64 (if (<= z -1.06e-88) x (- x (/ (* y z) t))))
double code(double x, double y, double z, double t) {
double tmp;
if (z <= -1.06e-88) {
tmp = x;
} else {
tmp = x - ((y * z) / t);
}
return tmp;
}
real(8) function code(x, y, z, t)
real(8), intent (in) :: x
real(8), intent (in) :: y
real(8), intent (in) :: z
real(8), intent (in) :: t
real(8) :: tmp
if (z <= (-1.06d-88)) then
tmp = x
else
tmp = x - ((y * z) / t)
end if
code = tmp
end function
public static double code(double x, double y, double z, double t) {
double tmp;
if (z <= -1.06e-88) {
tmp = x;
} else {
tmp = x - ((y * z) / t);
}
return tmp;
}
def code(x, y, z, t): tmp = 0 if z <= -1.06e-88: tmp = x else: tmp = x - ((y * z) / t) return tmp
function code(x, y, z, t) tmp = 0.0 if (z <= -1.06e-88) tmp = x; else tmp = Float64(x - Float64(Float64(y * z) / t)); end return tmp end
function tmp_2 = code(x, y, z, t) tmp = 0.0; if (z <= -1.06e-88) tmp = x; else tmp = x - ((y * z) / t); end tmp_2 = tmp; end
code[x_, y_, z_, t_] := If[LessEqual[z, -1.06e-88], x, N[(x - N[(N[(y * z), $MachinePrecision] / t), $MachinePrecision]), $MachinePrecision]]
\begin{array}{l}
\\
\begin{array}{l}
\mathbf{if}\;z \leq -1.06 \cdot 10^{-88}:\\
\;\;\;\;x\\
\mathbf{else}:\\
\;\;\;\;x - \frac{y \cdot z}{t}\\
\end{array}
\end{array}
if z < -1.06e-88Initial program 85.6%
associate-+l-87.6%
sub-neg87.6%
log1p-define98.0%
neg-sub098.0%
associate-+l-98.0%
neg-sub098.0%
+-commutative98.0%
unsub-neg98.0%
*-rgt-identity98.0%
distribute-lft-out--98.0%
expm1-define99.9%
Simplified99.9%
Taylor expanded in x around inf 72.1%
if -1.06e-88 < z Initial program 57.7%
associate-+l-78.6%
sub-neg78.6%
log1p-define78.6%
neg-sub078.6%
associate-+l-78.6%
neg-sub078.6%
+-commutative78.6%
unsub-neg78.6%
*-rgt-identity78.6%
distribute-lft-out--78.6%
expm1-define98.1%
Simplified98.1%
Taylor expanded in z around 0 93.6%
(FPCore (x y z t) :precision binary64 (if (<= z -1.06e-88) x (- x (* y (/ z t)))))
double code(double x, double y, double z, double t) {
double tmp;
if (z <= -1.06e-88) {
tmp = x;
} else {
tmp = x - (y * (z / t));
}
return tmp;
}
real(8) function code(x, y, z, t)
real(8), intent (in) :: x
real(8), intent (in) :: y
real(8), intent (in) :: z
real(8), intent (in) :: t
real(8) :: tmp
if (z <= (-1.06d-88)) then
tmp = x
else
tmp = x - (y * (z / t))
end if
code = tmp
end function
public static double code(double x, double y, double z, double t) {
double tmp;
if (z <= -1.06e-88) {
tmp = x;
} else {
tmp = x - (y * (z / t));
}
return tmp;
}
def code(x, y, z, t): tmp = 0 if z <= -1.06e-88: tmp = x else: tmp = x - (y * (z / t)) return tmp
function code(x, y, z, t) tmp = 0.0 if (z <= -1.06e-88) tmp = x; else tmp = Float64(x - Float64(y * Float64(z / t))); end return tmp end
function tmp_2 = code(x, y, z, t) tmp = 0.0; if (z <= -1.06e-88) tmp = x; else tmp = x - (y * (z / t)); end tmp_2 = tmp; end
code[x_, y_, z_, t_] := If[LessEqual[z, -1.06e-88], x, N[(x - N[(y * N[(z / t), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]]
\begin{array}{l}
\\
\begin{array}{l}
\mathbf{if}\;z \leq -1.06 \cdot 10^{-88}:\\
\;\;\;\;x\\
\mathbf{else}:\\
\;\;\;\;x - y \cdot \frac{z}{t}\\
\end{array}
\end{array}
if z < -1.06e-88Initial program 85.6%
associate-+l-87.6%
sub-neg87.6%
log1p-define98.0%
neg-sub098.0%
associate-+l-98.0%
neg-sub098.0%
+-commutative98.0%
unsub-neg98.0%
*-rgt-identity98.0%
distribute-lft-out--98.0%
expm1-define99.9%
Simplified99.9%
Taylor expanded in x around inf 72.1%
if -1.06e-88 < z Initial program 57.7%
associate-+l-78.6%
sub-neg78.6%
log1p-define78.6%
neg-sub078.6%
associate-+l-78.6%
neg-sub078.6%
+-commutative78.6%
unsub-neg78.6%
*-rgt-identity78.6%
distribute-lft-out--78.6%
expm1-define98.1%
Simplified98.1%
Taylor expanded in z around 0 93.6%
mul-1-neg93.6%
unsub-neg93.6%
associate-/l*93.0%
Simplified93.0%
(FPCore (x y z t) :precision binary64 x)
double code(double x, double y, double z, double t) {
return x;
}
real(8) function code(x, y, z, t)
real(8), intent (in) :: x
real(8), intent (in) :: y
real(8), intent (in) :: z
real(8), intent (in) :: t
code = x
end function
public static double code(double x, double y, double z, double t) {
return x;
}
def code(x, y, z, t): return x
function code(x, y, z, t) return x end
function tmp = code(x, y, z, t) tmp = x; end
code[x_, y_, z_, t_] := x
\begin{array}{l}
\\
x
\end{array}
Initial program 68.5%
associate-+l-82.1%
sub-neg82.1%
log1p-define86.1%
neg-sub086.1%
associate-+l-86.1%
neg-sub086.1%
+-commutative86.1%
unsub-neg86.1%
*-rgt-identity86.1%
distribute-lft-out--86.1%
expm1-define98.8%
Simplified98.8%
Taylor expanded in x around inf 76.4%
(FPCore (x y z t)
:precision binary64
(let* ((t_1 (/ (- 0.5) (* y t))))
(if (< z -2.8874623088207947e+119)
(- (- x (/ t_1 (* z z))) (* t_1 (/ (/ 2.0 z) (* z z))))
(- x (/ (log (+ 1.0 (* z y))) t)))))
double code(double x, double y, double z, double t) {
double t_1 = -0.5 / (y * t);
double tmp;
if (z < -2.8874623088207947e+119) {
tmp = (x - (t_1 / (z * z))) - (t_1 * ((2.0 / z) / (z * z)));
} else {
tmp = x - (log((1.0 + (z * y))) / t);
}
return tmp;
}
real(8) function code(x, y, z, t)
real(8), intent (in) :: x
real(8), intent (in) :: y
real(8), intent (in) :: z
real(8), intent (in) :: t
real(8) :: t_1
real(8) :: tmp
t_1 = -0.5d0 / (y * t)
if (z < (-2.8874623088207947d+119)) then
tmp = (x - (t_1 / (z * z))) - (t_1 * ((2.0d0 / z) / (z * z)))
else
tmp = x - (log((1.0d0 + (z * y))) / t)
end if
code = tmp
end function
public static double code(double x, double y, double z, double t) {
double t_1 = -0.5 / (y * t);
double tmp;
if (z < -2.8874623088207947e+119) {
tmp = (x - (t_1 / (z * z))) - (t_1 * ((2.0 / z) / (z * z)));
} else {
tmp = x - (Math.log((1.0 + (z * y))) / t);
}
return tmp;
}
def code(x, y, z, t): t_1 = -0.5 / (y * t) tmp = 0 if z < -2.8874623088207947e+119: tmp = (x - (t_1 / (z * z))) - (t_1 * ((2.0 / z) / (z * z))) else: tmp = x - (math.log((1.0 + (z * y))) / t) return tmp
function code(x, y, z, t) t_1 = Float64(Float64(-0.5) / Float64(y * t)) tmp = 0.0 if (z < -2.8874623088207947e+119) tmp = Float64(Float64(x - Float64(t_1 / Float64(z * z))) - Float64(t_1 * Float64(Float64(2.0 / z) / Float64(z * z)))); else tmp = Float64(x - Float64(log(Float64(1.0 + Float64(z * y))) / t)); end return tmp end
function tmp_2 = code(x, y, z, t) t_1 = -0.5 / (y * t); tmp = 0.0; if (z < -2.8874623088207947e+119) tmp = (x - (t_1 / (z * z))) - (t_1 * ((2.0 / z) / (z * z))); else tmp = x - (log((1.0 + (z * y))) / t); end tmp_2 = tmp; end
code[x_, y_, z_, t_] := Block[{t$95$1 = N[((-0.5) / N[(y * t), $MachinePrecision]), $MachinePrecision]}, If[Less[z, -2.8874623088207947e+119], N[(N[(x - N[(t$95$1 / N[(z * z), $MachinePrecision]), $MachinePrecision]), $MachinePrecision] - N[(t$95$1 * N[(N[(2.0 / z), $MachinePrecision] / N[(z * z), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]), $MachinePrecision], N[(x - N[(N[Log[N[(1.0 + N[(z * y), $MachinePrecision]), $MachinePrecision]], $MachinePrecision] / t), $MachinePrecision]), $MachinePrecision]]]
\begin{array}{l}
\\
\begin{array}{l}
t_1 := \frac{-0.5}{y \cdot t}\\
\mathbf{if}\;z < -2.8874623088207947 \cdot 10^{+119}:\\
\;\;\;\;\left(x - \frac{t\_1}{z \cdot z}\right) - t\_1 \cdot \frac{\frac{2}{z}}{z \cdot z}\\
\mathbf{else}:\\
\;\;\;\;x - \frac{\log \left(1 + z \cdot y\right)}{t}\\
\end{array}
\end{array}
herbie shell --seed 2024136
(FPCore (x y z t)
:name "System.Random.MWC.Distributions:truncatedExp from mwc-random-0.13.3.2"
:precision binary64
:alt
(! :herbie-platform default (if (< z -288746230882079470000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000) (- (- x (/ (/ (- 1/2) (* y t)) (* z z))) (* (/ (- 1/2) (* y t)) (/ (/ 2 z) (* z z)))) (- x (/ (log (+ 1 (* z y))) t))))
(- x (/ (log (+ (- 1.0 y) (* y (exp z)))) t)))