random - Limitation on irandom() of game maker?

I have three objects. All of them in the create event contain an action each (execute a piece of code):

obj_r01 => r01=0;

obj_r02 => r02=0;

obj_r03 => r03=0;

Image (to clarify what I have tried to explain):

So far so good, but I have one more object that modifies the variables of these other three: obj_control

The obj_control contains two events: create and draw.

crete event (obj_control):

obj_r01.r01=irandom(9);

obj_r02.r02=irandom(9);
obj_r03.r03=irandom(9);

draw event (obj_control):

This event contains three actions, precisely three "execute a piece of code":

piece one:

draw_text(x,y,obj_r01.r01); => applies to obj_r01

piece two:

draw_text(x,y,obj_r02.r02); => applies to obj_r02

piece three:

draw_text(x,y,obj_r03.r03); => applies to obj_r03

The objects are arranged as follows in the room:

In execution this is what happens:

The value of r01 is randomized, but that of r02 and r03 is not. I also tried to modify the obj_control creation event code to:

randomize();

obj_r01.r01=irandom(9);
randomize();
obj_r02.r02=irandom(9);
randomize();
obj_r03.r03=irandom(9);

However the result does not change. With this I could only suspect that the irandom () function can only create a storable random value, would it solve such a problem?

---

EDIT 1:

I tried putting randomize() only at the beginning of the code as suggested to me by @Philipp and @DH.:

randomize();
obj_r01.r01=irandom(9);
obj_r02.r02=irandom(9);
obj_r03.r03=irandom(9);

But there was no change in the result.

I also did a test to be sure if the value was not even being randomized or if the values ​​of r02 and r03 were being randomized to 0 and for that I modified their values ​​in the creation of each object:

In obj_r02:

r02=10

In obj_r03:

r03=100

The result:

The first value (not surprisingly) was randomized, but the second and third values ​​were not. Thus it is clear that the randomization is not being made or that the draw event is occurring before the radomization of r02 and r03.

Answer

The random number generator used by GameMaker is not a true random number generator. It is a pseudorandom number generator (or short: PRNG). A PRNG will return a sequence of numbers which look randomly, but are actually a deterministic sequence. The sequence of numbers a PRNG generates depends on its initial state, the so-called seed value. When you initialize a PRNG with the same seed, it will generate the same sequence.

That means that when you want each run of a game to be an unique experience, you need to use a different seed value for the PRNG for each run. As a developer you usually don't care where that value comes from, just that it isn't the same you already used. Game Maker's randomize function has the purpose to re-seed the random number generator with a new seed which is unlikely to be the same as the last time the game was run. I don't know what that function does exactly "under the hood" to achieve that, but it likely calculates the seed value from various entropy sources, like the current time, user input, etc. When you call randomize multiple times, those entropy sources might not have changed, so you re-initialize it again with the same seed. That means the PRNG will return the same sequence.

That means you generally should call randomize() exactly once: when the game starts. Then just call irandom(n) when you need a random number and it should return a different random number each time (or the same number... with a chance of one in n). So your game initialization function would look like this:

randomize();
obj_r01.r01=irandom(9);
obj_r02.r02=irandom(9);
obj_r03.r03=irandom(9);