
(FPCore (c x y) :precision binary64 (* c (log (+ 1.0 (* (- (pow E x) 1.0) y)))))
double code(double c, double x, double y) {
return c * log((1.0 + ((pow(((double) M_E), x) - 1.0) * y)));
}
public static double code(double c, double x, double y) {
return c * Math.log((1.0 + ((Math.pow(Math.E, x) - 1.0) * y)));
}
def code(c, x, y): return c * math.log((1.0 + ((math.pow(math.e, x) - 1.0) * y)))
function code(c, x, y) return Float64(c * log(Float64(1.0 + Float64(Float64((exp(1) ^ x) - 1.0) * y)))) end
function tmp = code(c, x, y) tmp = c * log((1.0 + (((2.71828182845904523536 ^ x) - 1.0) * y))); end
code[c_, x_, y_] := N[(c * N[Log[N[(1.0 + N[(N[(N[Power[E, x], $MachinePrecision] - 1.0), $MachinePrecision] * y), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]
c \cdot \log \left(1 + \left({e}^{x} - 1\right) \cdot y\right)
Herbie found 7 alternatives:
| Alternative | Accuracy | Speedup |
|---|
(FPCore (c x y) :precision binary64 (* c (log (+ 1.0 (* (- (pow E x) 1.0) y)))))
double code(double c, double x, double y) {
return c * log((1.0 + ((pow(((double) M_E), x) - 1.0) * y)));
}
public static double code(double c, double x, double y) {
return c * Math.log((1.0 + ((Math.pow(Math.E, x) - 1.0) * y)));
}
def code(c, x, y): return c * math.log((1.0 + ((math.pow(math.e, x) - 1.0) * y)))
function code(c, x, y) return Float64(c * log(Float64(1.0 + Float64(Float64((exp(1) ^ x) - 1.0) * y)))) end
function tmp = code(c, x, y) tmp = c * log((1.0 + (((2.71828182845904523536 ^ x) - 1.0) * y))); end
code[c_, x_, y_] := N[(c * N[Log[N[(1.0 + N[(N[(N[Power[E, x], $MachinePrecision] - 1.0), $MachinePrecision] * y), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]
c \cdot \log \left(1 + \left({e}^{x} - 1\right) \cdot y\right)
(FPCore (c x y)
:precision binary64
(let* ((t_0 (* c (log1p (* y (expm1 x))))))
(if (<= y -3600.0)
t_0
(if (<= y 2e-72)
(* y (fma -0.5 (* c (* y (pow (expm1 x) 2.0))) (* c (expm1 x))))
t_0))))double code(double c, double x, double y) {
double t_0 = c * log1p((y * expm1(x)));
double tmp;
if (y <= -3600.0) {
tmp = t_0;
} else if (y <= 2e-72) {
tmp = y * fma(-0.5, (c * (y * pow(expm1(x), 2.0))), (c * expm1(x)));
} else {
tmp = t_0;
}
return tmp;
}
function code(c, x, y) t_0 = Float64(c * log1p(Float64(y * expm1(x)))) tmp = 0.0 if (y <= -3600.0) tmp = t_0; elseif (y <= 2e-72) tmp = Float64(y * fma(-0.5, Float64(c * Float64(y * (expm1(x) ^ 2.0))), Float64(c * expm1(x)))); else tmp = t_0; end return tmp end
code[c_, x_, y_] := Block[{t$95$0 = N[(c * N[Log[1 + N[(y * N[(Exp[x] - 1), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]}, If[LessEqual[y, -3600.0], t$95$0, If[LessEqual[y, 2e-72], N[(y * N[(-0.5 * N[(c * N[(y * N[Power[N[(Exp[x] - 1), $MachinePrecision], 2.0], $MachinePrecision]), $MachinePrecision]), $MachinePrecision] + N[(c * N[(Exp[x] - 1), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]), $MachinePrecision], t$95$0]]]
\begin{array}{l}
t_0 := c \cdot \mathsf{log1p}\left(y \cdot \mathsf{expm1}\left(x\right)\right)\\
\mathbf{if}\;y \leq -3600:\\
\;\;\;\;t\_0\\
\mathbf{elif}\;y \leq 2 \cdot 10^{-72}:\\
\;\;\;\;y \cdot \mathsf{fma}\left(-0.5, c \cdot \left(y \cdot {\left(\mathsf{expm1}\left(x\right)\right)}^{2}\right), c \cdot \mathsf{expm1}\left(x\right)\right)\\
\mathbf{else}:\\
\;\;\;\;t\_0\\
\end{array}
if y < -3600 or 1.9999999999999999e-72 < y Initial program 41.9%
lift-log.f64N/A
lift-+.f64N/A
lower-log1p.f6456.7%
lift-*.f64N/A
*-commutativeN/A
lower-*.f6456.7%
lift--.f64N/A
lift-pow.f64N/A
lift-E.f64N/A
e-exp-1N/A
pow-expN/A
*-lft-identityN/A
lower-expm1.f6493.6%
Applied rewrites93.6%
if -3600 < y < 1.9999999999999999e-72Initial program 41.9%
lift-log.f64N/A
lift-+.f64N/A
lower-log1p.f6456.7%
lift-*.f64N/A
*-commutativeN/A
lower-*.f6456.7%
lift--.f64N/A
lift-pow.f64N/A
lift-E.f64N/A
e-exp-1N/A
pow-expN/A
*-lft-identityN/A
lower-expm1.f6493.6%
Applied rewrites93.6%
Taylor expanded in y around 0
lower-*.f64N/A
lower-fma.f64N/A
lower-*.f64N/A
lower-*.f64N/A
lower-pow.f64N/A
lower-expm1.f64N/A
lower-*.f64N/A
lower-expm1.f6476.7%
Applied rewrites76.7%
(FPCore (c x y) :precision binary64 (* c (log1p (* y (expm1 x)))))
double code(double c, double x, double y) {
return c * log1p((y * expm1(x)));
}
public static double code(double c, double x, double y) {
return c * Math.log1p((y * Math.expm1(x)));
}
def code(c, x, y): return c * math.log1p((y * math.expm1(x)))
function code(c, x, y) return Float64(c * log1p(Float64(y * expm1(x)))) end
code[c_, x_, y_] := N[(c * N[Log[1 + N[(y * N[(Exp[x] - 1), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]
c \cdot \mathsf{log1p}\left(y \cdot \mathsf{expm1}\left(x\right)\right)
Initial program 41.9%
lift-log.f64N/A
lift-+.f64N/A
lower-log1p.f6456.7%
lift-*.f64N/A
*-commutativeN/A
lower-*.f6456.7%
lift--.f64N/A
lift-pow.f64N/A
lift-E.f64N/A
e-exp-1N/A
pow-expN/A
*-lft-identityN/A
lower-expm1.f6493.6%
Applied rewrites93.6%
(FPCore (c x y)
:precision binary64
(let* ((t_0 (* (- (pow E x) 1.0) y)) (t_1 (* c (* y (expm1 x)))))
(if (<= t_0 -5e-291)
t_1
(if (<= t_0 0.0)
(* c (log1p (* y x)))
(if (<= t_0 1e-29) t_1 (* (log (fma y (expm1 x) 1.0)) c))))))double code(double c, double x, double y) {
double t_0 = (pow(((double) M_E), x) - 1.0) * y;
double t_1 = c * (y * expm1(x));
double tmp;
if (t_0 <= -5e-291) {
tmp = t_1;
} else if (t_0 <= 0.0) {
tmp = c * log1p((y * x));
} else if (t_0 <= 1e-29) {
tmp = t_1;
} else {
tmp = log(fma(y, expm1(x), 1.0)) * c;
}
return tmp;
}
function code(c, x, y) t_0 = Float64(Float64((exp(1) ^ x) - 1.0) * y) t_1 = Float64(c * Float64(y * expm1(x))) tmp = 0.0 if (t_0 <= -5e-291) tmp = t_1; elseif (t_0 <= 0.0) tmp = Float64(c * log1p(Float64(y * x))); elseif (t_0 <= 1e-29) tmp = t_1; else tmp = Float64(log(fma(y, expm1(x), 1.0)) * c); end return tmp end
code[c_, x_, y_] := Block[{t$95$0 = N[(N[(N[Power[E, x], $MachinePrecision] - 1.0), $MachinePrecision] * y), $MachinePrecision]}, Block[{t$95$1 = N[(c * N[(y * N[(Exp[x] - 1), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]}, If[LessEqual[t$95$0, -5e-291], t$95$1, If[LessEqual[t$95$0, 0.0], N[(c * N[Log[1 + N[(y * x), $MachinePrecision]], $MachinePrecision]), $MachinePrecision], If[LessEqual[t$95$0, 1e-29], t$95$1, N[(N[Log[N[(y * N[(Exp[x] - 1), $MachinePrecision] + 1.0), $MachinePrecision]], $MachinePrecision] * c), $MachinePrecision]]]]]]
\begin{array}{l}
t_0 := \left({e}^{x} - 1\right) \cdot y\\
t_1 := c \cdot \left(y \cdot \mathsf{expm1}\left(x\right)\right)\\
\mathbf{if}\;t\_0 \leq -5 \cdot 10^{-291}:\\
\;\;\;\;t\_1\\
\mathbf{elif}\;t\_0 \leq 0:\\
\;\;\;\;c \cdot \mathsf{log1p}\left(y \cdot x\right)\\
\mathbf{elif}\;t\_0 \leq 10^{-29}:\\
\;\;\;\;t\_1\\
\mathbf{else}:\\
\;\;\;\;\log \left(\mathsf{fma}\left(y, \mathsf{expm1}\left(x\right), 1\right)\right) \cdot c\\
\end{array}
if (*.f64 (-.f64 (pow.f64 (E.f64) x) #s(literal 1 binary64)) y) < -5.0000000000000003e-291 or -0.0 < (*.f64 (-.f64 (pow.f64 (E.f64) x) #s(literal 1 binary64)) y) < 9.99999999999999943e-30Initial program 41.9%
lift-log.f64N/A
lift-+.f64N/A
lower-log1p.f6456.7%
lift-*.f64N/A
*-commutativeN/A
lower-*.f6456.7%
lift--.f64N/A
lift-pow.f64N/A
lift-E.f64N/A
e-exp-1N/A
pow-expN/A
*-lft-identityN/A
lower-expm1.f6493.6%
Applied rewrites93.6%
Taylor expanded in y around 0
lower-*.f64N/A
lower-*.f64N/A
lower-expm1.f6474.0%
Applied rewrites74.0%
if -5.0000000000000003e-291 < (*.f64 (-.f64 (pow.f64 (E.f64) x) #s(literal 1 binary64)) y) < -0.0Initial program 41.9%
lift-log.f64N/A
lift-+.f64N/A
lower-log1p.f6456.7%
lift-*.f64N/A
*-commutativeN/A
lower-*.f6456.7%
lift--.f64N/A
lift-pow.f64N/A
lift-E.f64N/A
e-exp-1N/A
pow-expN/A
*-lft-identityN/A
lower-expm1.f6493.6%
Applied rewrites93.6%
Taylor expanded in x around 0
Applied rewrites66.5%
if 9.99999999999999943e-30 < (*.f64 (-.f64 (pow.f64 (E.f64) x) #s(literal 1 binary64)) y) Initial program 41.9%
lift-*.f64N/A
*-commutativeN/A
lower-*.f6441.9%
lift-+.f64N/A
+-commutativeN/A
lift-*.f64N/A
*-commutativeN/A
lower-fma.f6441.9%
lift--.f64N/A
lift-pow.f64N/A
lift-E.f64N/A
e-exp-1N/A
pow-expN/A
*-lft-identityN/A
lower-expm1.f6452.0%
Applied rewrites52.0%
(FPCore (c x y) :precision binary64 (if (<= x -0.009) (* c (* y (expm1 x))) (* c (log1p (* y x)))))
double code(double c, double x, double y) {
double tmp;
if (x <= -0.009) {
tmp = c * (y * expm1(x));
} else {
tmp = c * log1p((y * x));
}
return tmp;
}
public static double code(double c, double x, double y) {
double tmp;
if (x <= -0.009) {
tmp = c * (y * Math.expm1(x));
} else {
tmp = c * Math.log1p((y * x));
}
return tmp;
}
def code(c, x, y): tmp = 0 if x <= -0.009: tmp = c * (y * math.expm1(x)) else: tmp = c * math.log1p((y * x)) return tmp
function code(c, x, y) tmp = 0.0 if (x <= -0.009) tmp = Float64(c * Float64(y * expm1(x))); else tmp = Float64(c * log1p(Float64(y * x))); end return tmp end
code[c_, x_, y_] := If[LessEqual[x, -0.009], N[(c * N[(y * N[(Exp[x] - 1), $MachinePrecision]), $MachinePrecision]), $MachinePrecision], N[(c * N[Log[1 + N[(y * x), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]]
\begin{array}{l}
\mathbf{if}\;x \leq -0.009:\\
\;\;\;\;c \cdot \left(y \cdot \mathsf{expm1}\left(x\right)\right)\\
\mathbf{else}:\\
\;\;\;\;c \cdot \mathsf{log1p}\left(y \cdot x\right)\\
\end{array}
if x < -0.00899999999999999932Initial program 41.9%
lift-log.f64N/A
lift-+.f64N/A
lower-log1p.f6456.7%
lift-*.f64N/A
*-commutativeN/A
lower-*.f6456.7%
lift--.f64N/A
lift-pow.f64N/A
lift-E.f64N/A
e-exp-1N/A
pow-expN/A
*-lft-identityN/A
lower-expm1.f6493.6%
Applied rewrites93.6%
Taylor expanded in y around 0
lower-*.f64N/A
lower-*.f64N/A
lower-expm1.f6474.0%
Applied rewrites74.0%
if -0.00899999999999999932 < x Initial program 41.9%
lift-log.f64N/A
lift-+.f64N/A
lower-log1p.f6456.7%
lift-*.f64N/A
*-commutativeN/A
lower-*.f6456.7%
lift--.f64N/A
lift-pow.f64N/A
lift-E.f64N/A
e-exp-1N/A
pow-expN/A
*-lft-identityN/A
lower-expm1.f6493.6%
Applied rewrites93.6%
Taylor expanded in x around 0
Applied rewrites66.5%
(FPCore (c x y) :precision binary64 (if (<= x -2e-28) (* c (* y (expm1 x))) (* y (* c x))))
double code(double c, double x, double y) {
double tmp;
if (x <= -2e-28) {
tmp = c * (y * expm1(x));
} else {
tmp = y * (c * x);
}
return tmp;
}
public static double code(double c, double x, double y) {
double tmp;
if (x <= -2e-28) {
tmp = c * (y * Math.expm1(x));
} else {
tmp = y * (c * x);
}
return tmp;
}
def code(c, x, y): tmp = 0 if x <= -2e-28: tmp = c * (y * math.expm1(x)) else: tmp = y * (c * x) return tmp
function code(c, x, y) tmp = 0.0 if (x <= -2e-28) tmp = Float64(c * Float64(y * expm1(x))); else tmp = Float64(y * Float64(c * x)); end return tmp end
code[c_, x_, y_] := If[LessEqual[x, -2e-28], N[(c * N[(y * N[(Exp[x] - 1), $MachinePrecision]), $MachinePrecision]), $MachinePrecision], N[(y * N[(c * x), $MachinePrecision]), $MachinePrecision]]
\begin{array}{l}
\mathbf{if}\;x \leq -2 \cdot 10^{-28}:\\
\;\;\;\;c \cdot \left(y \cdot \mathsf{expm1}\left(x\right)\right)\\
\mathbf{else}:\\
\;\;\;\;y \cdot \left(c \cdot x\right)\\
\end{array}
if x < -1.99999999999999994e-28Initial program 41.9%
lift-log.f64N/A
lift-+.f64N/A
lower-log1p.f6456.7%
lift-*.f64N/A
*-commutativeN/A
lower-*.f6456.7%
lift--.f64N/A
lift-pow.f64N/A
lift-E.f64N/A
e-exp-1N/A
pow-expN/A
*-lft-identityN/A
lower-expm1.f6493.6%
Applied rewrites93.6%
Taylor expanded in y around 0
lower-*.f64N/A
lower-*.f64N/A
lower-expm1.f6474.0%
Applied rewrites74.0%
if -1.99999999999999994e-28 < x Initial program 41.9%
lift-log.f64N/A
lift-+.f64N/A
lower-log1p.f6456.7%
lift-*.f64N/A
*-commutativeN/A
lower-*.f6456.7%
lift--.f64N/A
lift-pow.f64N/A
lift-E.f64N/A
e-exp-1N/A
pow-expN/A
*-lft-identityN/A
lower-expm1.f6493.6%
Applied rewrites93.6%
Taylor expanded in y around 0
lower-*.f64N/A
lower-fma.f64N/A
lower-expm1.f64N/A
lower-*.f64N/A
Applied rewrites77.0%
Taylor expanded in x around 0
lower-*.f6459.2%
Applied rewrites59.2%
(FPCore (c x y) :precision binary64 (* (copysign 1.0 c) (if (<= (fabs c) 5e+54) (* (* (fabs c) y) x) (* y (* (fabs c) x)))))
double code(double c, double x, double y) {
double tmp;
if (fabs(c) <= 5e+54) {
tmp = (fabs(c) * y) * x;
} else {
tmp = y * (fabs(c) * x);
}
return copysign(1.0, c) * tmp;
}
public static double code(double c, double x, double y) {
double tmp;
if (Math.abs(c) <= 5e+54) {
tmp = (Math.abs(c) * y) * x;
} else {
tmp = y * (Math.abs(c) * x);
}
return Math.copySign(1.0, c) * tmp;
}
def code(c, x, y): tmp = 0 if math.fabs(c) <= 5e+54: tmp = (math.fabs(c) * y) * x else: tmp = y * (math.fabs(c) * x) return math.copysign(1.0, c) * tmp
function code(c, x, y) tmp = 0.0 if (abs(c) <= 5e+54) tmp = Float64(Float64(abs(c) * y) * x); else tmp = Float64(y * Float64(abs(c) * x)); end return Float64(copysign(1.0, c) * tmp) end
function tmp_2 = code(c, x, y) tmp = 0.0; if (abs(c) <= 5e+54) tmp = (abs(c) * y) * x; else tmp = y * (abs(c) * x); end tmp_2 = (sign(c) * abs(1.0)) * tmp; end
code[c_, x_, y_] := N[(N[With[{TMP1 = Abs[1.0], TMP2 = Sign[c]}, TMP1 * If[TMP2 == 0, 1, TMP2]], $MachinePrecision] * If[LessEqual[N[Abs[c], $MachinePrecision], 5e+54], N[(N[(N[Abs[c], $MachinePrecision] * y), $MachinePrecision] * x), $MachinePrecision], N[(y * N[(N[Abs[c], $MachinePrecision] * x), $MachinePrecision]), $MachinePrecision]]), $MachinePrecision]
\mathsf{copysign}\left(1, c\right) \cdot \begin{array}{l}
\mathbf{if}\;\left|c\right| \leq 5 \cdot 10^{+54}:\\
\;\;\;\;\left(\left|c\right| \cdot y\right) \cdot x\\
\mathbf{else}:\\
\;\;\;\;y \cdot \left(\left|c\right| \cdot x\right)\\
\end{array}
if c < 5.00000000000000005e54Initial program 41.9%
Taylor expanded in x around 0
lower-*.f64N/A
lower-fma.f64N/A
Applied rewrites54.6%
lift-*.f64N/A
*-commutativeN/A
lower-*.f6454.6%
Applied rewrites54.6%
Taylor expanded in x around 0
Applied rewrites61.6%
if 5.00000000000000005e54 < c Initial program 41.9%
lift-log.f64N/A
lift-+.f64N/A
lower-log1p.f6456.7%
lift-*.f64N/A
*-commutativeN/A
lower-*.f6456.7%
lift--.f64N/A
lift-pow.f64N/A
lift-E.f64N/A
e-exp-1N/A
pow-expN/A
*-lft-identityN/A
lower-expm1.f6493.6%
Applied rewrites93.6%
Taylor expanded in y around 0
lower-*.f64N/A
lower-fma.f64N/A
lower-expm1.f64N/A
lower-*.f64N/A
Applied rewrites77.0%
Taylor expanded in x around 0
lower-*.f6459.2%
Applied rewrites59.2%
(FPCore (c x y) :precision binary64 (* y (* c x)))
double code(double c, double x, double y) {
return y * (c * x);
}
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(c, x, y)
use fmin_fmax_functions
real(8), intent (in) :: c
real(8), intent (in) :: x
real(8), intent (in) :: y
code = y * (c * x)
end function
public static double code(double c, double x, double y) {
return y * (c * x);
}
def code(c, x, y): return y * (c * x)
function code(c, x, y) return Float64(y * Float64(c * x)) end
function tmp = code(c, x, y) tmp = y * (c * x); end
code[c_, x_, y_] := N[(y * N[(c * x), $MachinePrecision]), $MachinePrecision]
y \cdot \left(c \cdot x\right)
Initial program 41.9%
lift-log.f64N/A
lift-+.f64N/A
lower-log1p.f6456.7%
lift-*.f64N/A
*-commutativeN/A
lower-*.f6456.7%
lift--.f64N/A
lift-pow.f64N/A
lift-E.f64N/A
e-exp-1N/A
pow-expN/A
*-lft-identityN/A
lower-expm1.f6493.6%
Applied rewrites93.6%
Taylor expanded in y around 0
lower-*.f64N/A
lower-fma.f64N/A
lower-expm1.f64N/A
lower-*.f64N/A
Applied rewrites77.0%
Taylor expanded in x around 0
lower-*.f6459.2%
Applied rewrites59.2%
(FPCore (c x y) :precision binary64 (* c (log1p (* (expm1 x) y))))
double code(double c, double x, double y) {
return c * log1p((expm1(x) * y));
}
public static double code(double c, double x, double y) {
return c * Math.log1p((Math.expm1(x) * y));
}
def code(c, x, y): return c * math.log1p((math.expm1(x) * y))
function code(c, x, y) return Float64(c * log1p(Float64(expm1(x) * y))) end
code[c_, x_, y_] := N[(c * N[Log[1 + N[(N[(Exp[x] - 1), $MachinePrecision] * y), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]
c \cdot \mathsf{log1p}\left(\mathsf{expm1}\left(x\right) \cdot y\right)
herbie shell --seed 2025187
(FPCore (c x y)
:name "Logarithmic Transform"
:precision binary64
:alt
(* c (log1p (* (expm1 x) y)))
(* c (log (+ 1.0 (* (- (pow E x) 1.0) y)))))