
(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]
\begin{array}{l}
\\
c \cdot \log \left(1 + \left({e}^{x} - 1\right) \cdot y\right)
\end{array}
Sampling outcomes in binary64 precision:
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]
\begin{array}{l}
\\
c \cdot \log \left(1 + \left({e}^{x} - 1\right) \cdot y\right)
\end{array}
(FPCore (c x y)
:precision binary64
(if (<= y -1.6e-8)
(* (log1p (* (expm1 x) y)) c)
(if (<= y 470000000000.0)
(* (* (fma (* (pow (expm1 x) 2.0) y) -0.5 (expm1 x)) c) y)
(* (log1p (* x y)) c))))
double code(double c, double x, double y) {
double tmp;
if (y <= -1.6e-8) {
tmp = log1p((expm1(x) * y)) * c;
} else if (y <= 470000000000.0) {
tmp = (fma((pow(expm1(x), 2.0) * y), -0.5, expm1(x)) * c) * y;
} else {
tmp = log1p((x * y)) * c;
}
return tmp;
}
function code(c, x, y) tmp = 0.0 if (y <= -1.6e-8) tmp = Float64(log1p(Float64(expm1(x) * y)) * c); elseif (y <= 470000000000.0) tmp = Float64(Float64(fma(Float64((expm1(x) ^ 2.0) * y), -0.5, expm1(x)) * c) * y); else tmp = Float64(log1p(Float64(x * y)) * c); end return tmp end
code[c_, x_, y_] := If[LessEqual[y, -1.6e-8], N[(N[Log[1 + N[(N[(Exp[x] - 1), $MachinePrecision] * y), $MachinePrecision]], $MachinePrecision] * c), $MachinePrecision], If[LessEqual[y, 470000000000.0], N[(N[(N[(N[(N[Power[N[(Exp[x] - 1), $MachinePrecision], 2.0], $MachinePrecision] * y), $MachinePrecision] * -0.5 + N[(Exp[x] - 1), $MachinePrecision]), $MachinePrecision] * c), $MachinePrecision] * y), $MachinePrecision], N[(N[Log[1 + N[(x * y), $MachinePrecision]], $MachinePrecision] * c), $MachinePrecision]]]
\begin{array}{l}
\\
\begin{array}{l}
\mathbf{if}\;y \leq -1.6 \cdot 10^{-8}:\\
\;\;\;\;\mathsf{log1p}\left(\mathsf{expm1}\left(x\right) \cdot y\right) \cdot c\\
\mathbf{elif}\;y \leq 470000000000:\\
\;\;\;\;\left(\mathsf{fma}\left({\left(\mathsf{expm1}\left(x\right)\right)}^{2} \cdot y, -0.5, \mathsf{expm1}\left(x\right)\right) \cdot c\right) \cdot y\\
\mathbf{else}:\\
\;\;\;\;\mathsf{log1p}\left(x \cdot y\right) \cdot c\\
\end{array}
\end{array}
if y < -1.6000000000000001e-8Initial program 54.5%
lift-*.f64N/A
lift-log.f64N/A
lift-+.f64N/A
lift-*.f64N/A
lift--.f64N/A
lift-E.f64N/A
lift-pow.f64N/A
*-commutativeN/A
lower-*.f64N/A
Applied rewrites99.8%
Taylor expanded in x around 0
Applied rewrites99.8%
if -1.6000000000000001e-8 < y < 4.7e11Initial program 41.5%
lift-*.f64N/A
lift-log.f64N/A
lift-+.f64N/A
lift-*.f64N/A
lift--.f64N/A
lift-E.f64N/A
lift-pow.f64N/A
*-commutativeN/A
lower-*.f64N/A
Applied rewrites90.5%
Taylor expanded in x around 0
Applied rewrites90.5%
Taylor expanded in y around 0
*-commutativeN/A
lower-*.f64N/A
Applied rewrites99.2%
Taylor expanded in c around 0
*-commutativeN/A
lower-*.f64N/A
Applied rewrites99.2%
if 4.7e11 < y Initial program 17.1%
lift-*.f64N/A
lift-log.f64N/A
lift-+.f64N/A
lift-*.f64N/A
lift--.f64N/A
lift-E.f64N/A
lift-pow.f64N/A
*-commutativeN/A
lower-*.f64N/A
Applied rewrites99.6%
Taylor expanded in x around 0
Applied rewrites99.6%
Final simplification99.4%
(FPCore (c x y) :precision binary64 (if (<= (- (pow E x) 1.0) -1.0) (* (* (expm1 x) y) c) (* (log1p (* x y)) c)))
double code(double c, double x, double y) {
double tmp;
if ((pow(((double) M_E), x) - 1.0) <= -1.0) {
tmp = (expm1(x) * y) * c;
} else {
tmp = log1p((x * y)) * c;
}
return tmp;
}
public static double code(double c, double x, double y) {
double tmp;
if ((Math.pow(Math.E, x) - 1.0) <= -1.0) {
tmp = (Math.expm1(x) * y) * c;
} else {
tmp = Math.log1p((x * y)) * c;
}
return tmp;
}
def code(c, x, y): tmp = 0 if (math.pow(math.e, x) - 1.0) <= -1.0: tmp = (math.expm1(x) * y) * c else: tmp = math.log1p((x * y)) * c return tmp
function code(c, x, y) tmp = 0.0 if (Float64((exp(1) ^ x) - 1.0) <= -1.0) tmp = Float64(Float64(expm1(x) * y) * c); else tmp = Float64(log1p(Float64(x * y)) * c); end return tmp end
code[c_, x_, y_] := If[LessEqual[N[(N[Power[E, x], $MachinePrecision] - 1.0), $MachinePrecision], -1.0], N[(N[(N[(Exp[x] - 1), $MachinePrecision] * y), $MachinePrecision] * c), $MachinePrecision], N[(N[Log[1 + N[(x * y), $MachinePrecision]], $MachinePrecision] * c), $MachinePrecision]]
\begin{array}{l}
\\
\begin{array}{l}
\mathbf{if}\;{e}^{x} - 1 \leq -1:\\
\;\;\;\;\left(\mathsf{expm1}\left(x\right) \cdot y\right) \cdot c\\
\mathbf{else}:\\
\;\;\;\;\mathsf{log1p}\left(x \cdot y\right) \cdot c\\
\end{array}
\end{array}
if (-.f64 (pow.f64 (E.f64) x) #s(literal 1 binary64)) < -1Initial program 58.6%
lift-*.f64N/A
lift-log.f64N/A
lift-+.f64N/A
lift-*.f64N/A
lift--.f64N/A
lift-E.f64N/A
lift-pow.f64N/A
*-commutativeN/A
lower-*.f64N/A
Applied rewrites99.9%
Taylor expanded in y around 0
lift-expm1.f64N/A
*-rgt-identityN/A
lower-expm1.f64N/A
*-rgt-identityN/A
*-commutativeN/A
log-EN/A
pow-to-expN/A
lower-expm1.f64N/A
*-rgt-identityN/A
lift-expm1.f64N/A
*-commutativeN/A
lift-expm1.f64N/A
lift-*.f64N/A
lift-*.f6465.9
lift-*.f64N/A
*-rgt-identity65.9
Applied rewrites65.9%
if -1 < (-.f64 (pow.f64 (E.f64) x) #s(literal 1 binary64)) Initial program 32.1%
lift-*.f64N/A
lift-log.f64N/A
lift-+.f64N/A
lift-*.f64N/A
lift--.f64N/A
lift-E.f64N/A
lift-pow.f64N/A
*-commutativeN/A
lower-*.f64N/A
Applied rewrites91.4%
Taylor expanded in x around 0
Applied rewrites91.0%
(FPCore (c x y) :precision binary64 (* (log1p (* (expm1 x) y)) c))
double code(double c, double x, double y) {
return log1p((expm1(x) * y)) * c;
}
public static double code(double c, double x, double y) {
return Math.log1p((Math.expm1(x) * y)) * c;
}
def code(c, x, y): return math.log1p((math.expm1(x) * y)) * c
function code(c, x, y) return Float64(log1p(Float64(expm1(x) * y)) * c) end
code[c_, x_, y_] := N[(N[Log[1 + N[(N[(Exp[x] - 1), $MachinePrecision] * y), $MachinePrecision]], $MachinePrecision] * c), $MachinePrecision]
\begin{array}{l}
\\
\mathsf{log1p}\left(\mathsf{expm1}\left(x\right) \cdot y\right) \cdot c
\end{array}
Initial program 40.9%
lift-*.f64N/A
lift-log.f64N/A
lift-+.f64N/A
lift-*.f64N/A
lift--.f64N/A
lift-E.f64N/A
lift-pow.f64N/A
*-commutativeN/A
lower-*.f64N/A
Applied rewrites94.2%
Taylor expanded in x around 0
Applied rewrites94.2%
(FPCore (c x y) :precision binary64 (if (<= x -4.7e-169) (* (* (expm1 x) y) c) (* (* c x) y)))
double code(double c, double x, double y) {
double tmp;
if (x <= -4.7e-169) {
tmp = (expm1(x) * y) * c;
} else {
tmp = (c * x) * y;
}
return tmp;
}
public static double code(double c, double x, double y) {
double tmp;
if (x <= -4.7e-169) {
tmp = (Math.expm1(x) * y) * c;
} else {
tmp = (c * x) * y;
}
return tmp;
}
def code(c, x, y): tmp = 0 if x <= -4.7e-169: tmp = (math.expm1(x) * y) * c else: tmp = (c * x) * y return tmp
function code(c, x, y) tmp = 0.0 if (x <= -4.7e-169) tmp = Float64(Float64(expm1(x) * y) * c); else tmp = Float64(Float64(c * x) * y); end return tmp end
code[c_, x_, y_] := If[LessEqual[x, -4.7e-169], N[(N[(N[(Exp[x] - 1), $MachinePrecision] * y), $MachinePrecision] * c), $MachinePrecision], N[(N[(c * x), $MachinePrecision] * y), $MachinePrecision]]
\begin{array}{l}
\\
\begin{array}{l}
\mathbf{if}\;x \leq -4.7 \cdot 10^{-169}:\\
\;\;\;\;\left(\mathsf{expm1}\left(x\right) \cdot y\right) \cdot c\\
\mathbf{else}:\\
\;\;\;\;\left(c \cdot x\right) \cdot y\\
\end{array}
\end{array}
if x < -4.6999999999999999e-169Initial program 46.0%
lift-*.f64N/A
lift-log.f64N/A
lift-+.f64N/A
lift-*.f64N/A
lift--.f64N/A
lift-E.f64N/A
lift-pow.f64N/A
*-commutativeN/A
lower-*.f64N/A
Applied rewrites99.2%
Taylor expanded in y around 0
lift-expm1.f64N/A
*-rgt-identityN/A
lower-expm1.f64N/A
*-rgt-identityN/A
*-commutativeN/A
log-EN/A
pow-to-expN/A
lower-expm1.f64N/A
*-rgt-identityN/A
lift-expm1.f64N/A
*-commutativeN/A
lift-expm1.f64N/A
lift-*.f64N/A
lift-*.f6469.6
lift-*.f64N/A
*-rgt-identity69.6
Applied rewrites69.6%
if -4.6999999999999999e-169 < x Initial program 36.2%
Taylor expanded in x around 0
associate-*r*N/A
log-EN/A
lower-*.f64N/A
lower-*.f64N/A
lower-*.f6481.7
Applied rewrites81.7%
lift-*.f64N/A
*-rgt-identity81.7
Applied rewrites81.7%
(FPCore (c x y) :precision binary64 (if (<= c 3.5e-22) (* (fma (* (fma (* c y) -0.5 (* 0.5 c)) y) x (* c y)) x) (* (* c x) y)))
double code(double c, double x, double y) {
double tmp;
if (c <= 3.5e-22) {
tmp = fma((fma((c * y), -0.5, (0.5 * c)) * y), x, (c * y)) * x;
} else {
tmp = (c * x) * y;
}
return tmp;
}
function code(c, x, y) tmp = 0.0 if (c <= 3.5e-22) tmp = Float64(fma(Float64(fma(Float64(c * y), -0.5, Float64(0.5 * c)) * y), x, Float64(c * y)) * x); else tmp = Float64(Float64(c * x) * y); end return tmp end
code[c_, x_, y_] := If[LessEqual[c, 3.5e-22], N[(N[(N[(N[(N[(c * y), $MachinePrecision] * -0.5 + N[(0.5 * c), $MachinePrecision]), $MachinePrecision] * y), $MachinePrecision] * x + N[(c * y), $MachinePrecision]), $MachinePrecision] * x), $MachinePrecision], N[(N[(c * x), $MachinePrecision] * y), $MachinePrecision]]
\begin{array}{l}
\\
\begin{array}{l}
\mathbf{if}\;c \leq 3.5 \cdot 10^{-22}:\\
\;\;\;\;\mathsf{fma}\left(\mathsf{fma}\left(c \cdot y, -0.5, 0.5 \cdot c\right) \cdot y, x, c \cdot y\right) \cdot x\\
\mathbf{else}:\\
\;\;\;\;\left(c \cdot x\right) \cdot y\\
\end{array}
\end{array}
if c < 3.50000000000000005e-22Initial program 46.3%
lift-*.f64N/A
lift-log.f64N/A
lift-+.f64N/A
lift-*.f64N/A
lift--.f64N/A
lift-E.f64N/A
lift-pow.f64N/A
*-commutativeN/A
lower-*.f64N/A
Applied rewrites94.6%
Taylor expanded in x around 0
Applied rewrites94.6%
Taylor expanded in y around 0
*-commutativeN/A
lower-*.f64N/A
Applied rewrites75.0%
Taylor expanded in x around 0
*-commutativeN/A
lower-*.f64N/A
+-commutativeN/A
*-commutativeN/A
lower-fma.f64N/A
*-commutativeN/A
lower-*.f64N/A
*-commutativeN/A
lower-fma.f64N/A
lower-*.f64N/A
lower-*.f64N/A
lower-*.f6459.3
Applied rewrites59.3%
if 3.50000000000000005e-22 < c Initial program 24.2%
Taylor expanded in x around 0
associate-*r*N/A
log-EN/A
lower-*.f64N/A
lower-*.f64N/A
lower-*.f6462.7
Applied rewrites62.7%
lift-*.f64N/A
*-rgt-identity62.7
Applied rewrites62.7%
Final simplification60.1%
(FPCore (c x y) :precision binary64 (if (<= c 4e-28) (* (* y x) c) (* (* c x) y)))
double code(double c, double x, double y) {
double tmp;
if (c <= 4e-28) {
tmp = (y * x) * c;
} else {
tmp = (c * x) * y;
}
return tmp;
}
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
real(8) :: tmp
if (c <= 4d-28) then
tmp = (y * x) * c
else
tmp = (c * x) * y
end if
code = tmp
end function
public static double code(double c, double x, double y) {
double tmp;
if (c <= 4e-28) {
tmp = (y * x) * c;
} else {
tmp = (c * x) * y;
}
return tmp;
}
def code(c, x, y): tmp = 0 if c <= 4e-28: tmp = (y * x) * c else: tmp = (c * x) * y return tmp
function code(c, x, y) tmp = 0.0 if (c <= 4e-28) tmp = Float64(Float64(y * x) * c); else tmp = Float64(Float64(c * x) * y); end return tmp end
function tmp_2 = code(c, x, y) tmp = 0.0; if (c <= 4e-28) tmp = (y * x) * c; else tmp = (c * x) * y; end tmp_2 = tmp; end
code[c_, x_, y_] := If[LessEqual[c, 4e-28], N[(N[(y * x), $MachinePrecision] * c), $MachinePrecision], N[(N[(c * x), $MachinePrecision] * y), $MachinePrecision]]
\begin{array}{l}
\\
\begin{array}{l}
\mathbf{if}\;c \leq 4 \cdot 10^{-28}:\\
\;\;\;\;\left(y \cdot x\right) \cdot c\\
\mathbf{else}:\\
\;\;\;\;\left(c \cdot x\right) \cdot y\\
\end{array}
\end{array}
if c < 3.99999999999999988e-28Initial program 46.2%
lift-*.f64N/A
lift-log.f64N/A
lift-+.f64N/A
lift-*.f64N/A
lift--.f64N/A
lift-E.f64N/A
lift-pow.f64N/A
*-commutativeN/A
lower-*.f64N/A
Applied rewrites94.5%
Taylor expanded in x around 0
lift-expm1.f64N/A
*-rgt-identityN/A
lower-expm1.f64N/A
*-rgt-identityN/A
*-commutativeN/A
log-EN/A
pow-to-expN/A
*-commutativeN/A
lower-*.f6456.0
Applied rewrites56.0%
if 3.99999999999999988e-28 < c Initial program 25.0%
Taylor expanded in x around 0
associate-*r*N/A
log-EN/A
lower-*.f64N/A
lower-*.f64N/A
lower-*.f6462.4
Applied rewrites62.4%
lift-*.f64N/A
*-rgt-identity62.4
Applied rewrites62.4%
(FPCore (c x y) :precision binary64 (* (* c x) y))
double code(double c, double x, double y) {
return (c * x) * y;
}
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 = (c * x) * y
end function
public static double code(double c, double x, double y) {
return (c * x) * y;
}
def code(c, x, y): return (c * x) * y
function code(c, x, y) return Float64(Float64(c * x) * y) end
function tmp = code(c, x, y) tmp = (c * x) * y; end
code[c_, x_, y_] := N[(N[(c * x), $MachinePrecision] * y), $MachinePrecision]
\begin{array}{l}
\\
\left(c \cdot x\right) \cdot y
\end{array}
Initial program 40.9%
Taylor expanded in x around 0
associate-*r*N/A
log-EN/A
lower-*.f64N/A
lower-*.f64N/A
lower-*.f6457.5
Applied rewrites57.5%
lift-*.f64N/A
*-rgt-identity57.5
Applied rewrites57.5%
(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]
\begin{array}{l}
\\
c \cdot \mathsf{log1p}\left(\mathsf{expm1}\left(x\right) \cdot y\right)
\end{array}
herbie shell --seed 2025072
(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)))))