Mandelbrot thingy with Allegro

#include <iostream>
#include <complex>
#include <vector>
#include <allegro5/allegro.h>
#include <allegro5/allegro_image.h>

const int MANDELBROT_RESOLUTION_W = 2000;
const int MANDELBROT_RESOLUTION_H = 2000;
const unsigned int ITERATIONS = 100;

inline float complex_length_squared(const std::complex<float>& cmplx) {
    return cmplx.real()*cmplx.real() + cmplx.imag()*cmplx.imag();
}

inline float lin_interpol(float p1, float p2, float rate) {
    return p1 + (p2-p1)*rate;
}

int main()
{
   al_init();
   al_init_image_addon();
   ALLEGRO_BITMAP* bitmap = al_create_bitmap(MANDELBROT_RESOLUTION_W, MANDELBROT_RESOLUTION_H);

   std::vector<std::complex<float>> setCandidates;
   setCandidates.reserve(MANDELBROT_RESOLUTION_W * MANDELBROT_RESOLUTION_H);
   for(int i = 0; i<MANDELBROT_RESOLUTION_W; ++i) {
       for(int j = 0; j<MANDELBROT_RESOLUTION_H; ++j) {
           setCandidates.push_back(std::complex<float>(lin_interpol(-2,2,i/static_cast<float>(MANDELBROT_RESOLUTION_W)),
                                                       lin_interpol(-2,2,j/static_cast<float>(MANDELBROT_RESOLUTION_H))));
       }
   }
   std::vector<std::complex<float>> discriminants(MANDELBROT_RESOLUTION_W*MANDELBROT_RESOLUTION_H,1);
   std::vector<int> escapeChecker(MANDELBROT_RESOLUTION_W * MANDELBROT_RESOLUTION_H, 0);
   for(int currentIteration = 1; currentIteration <= ITERATIONS; ++currentIteration) {
       for(int i = 0; i< MANDELBROT_RESOLUTION_W; ++i) {
            for(int j=0; j<MANDELBROT_RESOLUTION_H; ++j) {
                if(escapeChecker[i]) continue;
                discriminants[i*MANDELBROT_RESOLUTION_H+j] *= discriminants[i*MANDELBROT_RESOLUTION_H+j];
                discriminants[i*MANDELBROT_RESOLUTION_H+j] += setCandidates[i*MANDELBROT_RESOLUTION_H+j];
                float length = complex_length_squared(discriminants[i*MANDELBROT_RESOLUTION_H+j]);
                if(length > 2) {
                   escapeChecker[i*MANDELBROT_RESOLUTION_H+j] = currentIteration;
                }
            }
       }

   }
   al_set_target_bitmap(bitmap);
   al_clear_to_color(al_map_rgb(0,0,0));
   for(int i=0; i<MANDELBROT_RESOLUTION_W; ++i) {
       for(int j=0; j<MANDELBROT_RESOLUTION_H; ++j) {
           int escaped = escapeChecker[i*MANDELBROT_RESOLUTION_H+j];
           if(escaped) {
               float rate = static_cast<float>(escaped)/ITERATIONS;
               al_draw_pixel(i,j,al_map_rgb(static_cast<unsigned char>(lin_interpol(0,255,rate)),
                                            0,
                                            static_cast<unsigned char>(lin_interpol(255,0,rate))));
           }
       }
   }

   al_save_bitmap("mandelbrot.png",bitmap);

   al_destroy_bitmap(bitmap);
}