Why do I get either a double free or corruption (out) or a C malloc assertion failure? - gcc

Question

I am writing a code for a physics simulation, evolving some copies of the initial state with a stochastic and a deterministic evolution, returning the the value of some observable at each timestep of the simulation. I am using Armadillo (version 11.4.3) for handling the linear algebra and C++ vector to allocate memory. I am running it on Ubuntu. The code is something like this:
vec class::run (bool verbose) const { // verbose = true => prints some trajectories and the exact result
vec observables(_num_timesteps);
int n_observable = 0;
// Allocating _N_ensemble copies of the initial state
std::vector<cx_vec> psi(_N_ensemble);
for (int i = 0; i <= _N_ensemble; ++i)
psi[i] = _initial_state;
// Exact solution and printing some of the trajectories
cx_mat rho_ex(_dim, _dim);
rho_ex = projector(_initial_state);
ofstream out_ex, traj;
if (verbose) {
out_ex.open("exact.txt");
traj.open("trajectories.txt");
}
for (double t = 0.; t <= _t_f; t += _dt) { // Time evolution
if (verbose) { // Prints and evolves the exact solution
out_ex << observable(rho_ex) << endl;
rho_ex = exact_evolution(rho_ex,t)
}
cx_mat rho(_dim, _dim, fill::zeros); // Average state
for (int i = 0; i < _N_ensemble; ++i) { // Cycle on the ensemble members
if (verbose && i < _N_traj_print) // Prints some trajectories
traj << observable(projector(psi[i])) << " ";
rho += projector(psi[i])/((double)_N_ensemble);
psi[i] = evolve(psi[i],t);
}
// Storing the observable
observables[n_observable] = observable(rho);
n_observable++;
if (verbose) traj << endl;
}
return observables;
}
All the variables starting with an underscore are supposed to be member variables of the class.
The idea is to execute run(verbose) N times. For the first execution, everything works fine (as long as _N_ensemble is sufficiently big: if _N_ensemble=1000 everything is fine, if _N_ensemble=100 I get a C malloc assertion failure; see the following for more details).
The problems appear the second time I try to execute it the second time. If I run it with verbose=false, it correctly arrives at the end of the function, but when returning observables, it throws the error
double free or corruption (out)
If I run it with verbose=true, it stops during the for cycle on i with t=0, giving a C malloc assertion failure:
malloc.c:2617: sysmalloc: Assertion `(old_top == initial_top (av) && old_size == 0) || ((unsigned long) (old_size) >= MINSIZE && prev_inuse (old_top) && ((unsigned long) old_end & (pagesize - 1)) == 0)' failed.
I have no idea why it throws those errors, since all the allocation of memory is be handled by C++ vector and not by me directly, and why it only happens during the second run. Does anyone have any idea why it happens?
Interestingly, if I run the same code on MacOS, everything works fine and I don´t get those errors.
I tried clearing the allocated vectors manually, but nothing changes.