I do not understand why `HCubature.jl`

`v1.6.0`

makes two different estimates of the error `E`

(HCubature.jl/src/HCubature.jl at master · JuliaMath/HCubature.jl · GitHub) for the following two versions of the integrand:

```
using HCubature
function singlet(f)
Δf² = 0.5^2
100 * Δf² / (Δf² + 4*f^2)
end
normInf(x) = norm(x, Inf)
freqs = -2:0.01:2
δf, res = zeros(length(freqs)), zeros(length(freqs))
function integr(ppt)
ρ, z = ppt
δf .= freqs .- (z^2 + 0.5z - 0.5ρ^2)
res .= 2π * ρ * singlet.(δf)
res
end
function integr2(ppt)
ρ, z = ppt
δf = freqs .- (z^2 + 0.5z - 0.5ρ^2)
res = 2π * ρ * singlet.(δf)
res
end
a, b = (0, -1.2), (1, +1.2)
r1, _ = hcubature(integr, a, b; rtol=1e-2, atol=0.5,
maxevals=100_000, norm=normInf)
r2, _ = hcubature(integr2, a, b; rtol=1e-2, atol=0.5,
maxevals=100_000, norm=normInf)
```

The integration with `integr`

terminates when `maxeval=100_000`

is reached, `integr2`

requires about 1000 evaluations.