`pqn` may break `vmin/vmax` limits

[kerim371]

Hi,

While working on Viking Graben JUDI's PR I've encountered a situation when at some iteration the pqn algorithm with TV condition crosses the vmin/vmax boundary condition.

For example my code:

# SETUP CONSTARAINTS
options=PARSDMM_options()
options.FL=Float32
options=default_PARSDMM_options(options,options.FL)
constraint = Vector{SetIntersectionProjection.set_definitions}()

# Bound constraints
vmin = 1.2
vmax = 5.2

# Slowness squared [s^2/km^2]
mmin = (1f0 ./ vmax).^2
mmax = (1f0 ./ vmin).^2
mminArr = ones(Float32, size(model0)) .* mmin
mmaxArr = ones(Float32, size(model0)) .* mmax

# bounds:
set_type = "bounds"
TD_OP = "identity"
app_mode = ("matrix","")
custom_TD_OP = ([],false)
push!(constraint, set_definitions(set_type,TD_OP,vec(mminArr),vec(mmaxArr),app_mode,custom_TD_OP));

#TV
(TV,dummy1,dummy2,dummy3) = get_TD_operator(model0.m,"TV",options.FL)
mvar_min = 0.0
mvar_max = norm(TV*vec(m0),1) * 1.0
set_type = "l1"
TD_OP = "TV"
app_mode = ("matrix","")
custom_TD_OP = ([],false)
push!(constraint, set_definitions(set_type,TD_OP,mvar_min,mvar_max,app_mode,custom_TD_OP));

Here is the result of 8 9 and 10 iterations:

As you can see 9th iteration brings up values about 11 km/s (there is no clipping values during the imshow and the colorbar's range reflects min/max values in the array) even when the borders are [1.2, 5.2]

P.S. 15 iterations at 3.5 Hz passed correctly.