Fastplotlib: GPU-accelerated, fast, and interactive plotting library(medium.com)

    #define FPS 80

    void plot_points(
                    float *o,  // output raster array (w*h)
                    int w,     // width of raster
                    int h,     // height of raster
                    float *x,  // input point coordinates (2*n)
                    int n      // number of input points
                    )
    {
            // initialize the output raster
            for (int i = 0; i < 2*w*h; i++)
                    o[i] = 0;
    
            // accumulate the points that fall inside the raster
            for (int i = 0; i < n; i++)
            {
                    int p = x[2*i+0];
                    int q = x[2*i+1];
                    if (p >= 0 && p < w && q >= 0 && q < h)
                            o[w*q+p] += 1;
            }
    }
    
    #include <stdlib.h>
    int main(void)
    {
            int w = 1000;
            int h = 1000;
            int n = 3000000;
            float *x = malloc(2*n*sizeof*x);
            float *o = malloc(w*h*sizeof*o);
            for (int i = 0; i < 2*n; i++)
                    x[i] = 1000*(rand()/(1.0+RAND_MAX));
            for (int i = 0; i < FPS ; i++)
                    plot_points(o, w, h, x, n);
            return 0;
    }
    // NOTE: if this program runs in less than 1 second, it means that it
    // is faster than "FPS"