Alternative ways to draw pixels or lines on screen - c

Question

I define my SDL2 window as follows:
SDL_Init(SDL_INIT_EVERYTHING);
SDL_GL_SetAttribute(SDL_GL_RED_SIZE, 8); // red: 8 bits
SDL_GL_SetAttribute(SDL_GL_GREEN_SIZE, 8); // green: 8 bits
SDL_GL_SetAttribute(SDL_GL_BLUE_SIZE, 8); // blue: 8 bits
SDL_GL_SetAttribute(SDL_GL_ALPHA_SIZE, 8); // alpha: 8 bits
SDL_GL_SetAttribute(SDL_GL_BUFFER_SIZE, 32); // r + g + b + a = 32 bits
SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
graphWindow = SDL_CreateWindow(title, SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, width, height, SDL_WINDOW_OPENGL);
Then, with the following struct, I create an array of pixels and use that array as the buffer that is passed to SDL:
typedef struct {
float r;
float g;
float b;
float a;
} Pixel;
// ...
void main(void) {
Pixel *pixels;
// ...
pixels = malloc(width * height * sizeof(Pixel));
// ...
glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
while (graphNotClosed) {
glDrawPixels(width, height, GL_RGBA, GL_FLOAT, pixels);
// do some number cruching and change some elements of array "pixels"
// ...
SDL_GL_SwapWindow(graphWindow);
}
}
The thing that bothers me is, though the code sometimes change one and only one pixel in the while loop, I still keep passing the whole array (with width * height) to the SDL (via glDrawPixels) in each iteration.
And my question: Is this a must (and only way) to pass the whole array to SDL or is it possible to inform the SDL just the pixel(s) that had been altered from the previous state, in the name of accelerating the graphics process.