I first made these tests with three different civs: the Romans, the Persians and the Mongols. to speed things upI prepared a map with many trade bonus icons and choosed 2x2x settings, King. Meanwhile I veryfied on deity and 1x1x settings. also i put the AI civs on a far crappy island in order to prevent them from disturbing my circles.
one thing always remained the same: the tech path I was choosing. it is Horsebackriding -> Ceremonial Burial -> Alphabet ->Law Code -> Monarchy -> Writing. whatever settings I choosed the results were always the same.

anyway, I was playing with the Romans, the Persians and the Mongols and always got the same tech-tables. here they are:

3950:
Alphabet
BronzeCeremonial Burial
Horsebackriding
Masonary
Pottery
Warrior Code

3850:
Alphabet
Ceremonial Burial
Wheel

3650:
Alphabet
Bronze
Masonary
Mysicism
Polytheism
Pottery
Warrior Code

3500:
Bronze
Law Code
Masonary
Mysticism
Pottery
Warrior Code
Wheel

3350:
Bronze
Map Making
Monarchy
Polytheism
Wheel
Writing

3150:
Bronze
Map Making
Masonary
Mysticism
Polytheism
Pottery
Warrior Code
Writing

2950:
Bronze
Masonary
Mysticism
Pottery
Warrior Code
Wheel

quote: Originally posted by oedo on 12-01-2000 10:18 AM ... the techs allowed for choosing aren´t random at all. they also aren´t influenced by the civ you´re playing. but they´re determined in a probably very complicated way.

[1] The technology you already have
[2] The moment you discovered the key techs Warrior Code and Navigation. If you get one of these early, the options will be different.

Most likely there is not a formula but a table / several tables.

- is there difference between regular researched techs in comparison to starting techs/hut techs?

- what´s up with the warrior code/navigation thing? (very interesting aspect)

- certain questions which will most probably arise during my further tests

I will add more research table the coming days.

BTW, I posted my dream-tech-tree, which unfortunately doesn´t work, into SG´s Alphabet thread. This one here works: Alphabet->Map Making->Pottery->Seafaring.

FE I can never seem to reserarch Ceremonial Curial, then Code of Laws, then Monarchy. After researching the first two in a row, all social techs are unavailable.

Also, oedo, I believe that starting techs don't slow down the tech rate as other techs do. Thats why its a big host advantage to get them in multiplayer. If a civ starts with say 2 technologies, they still only need 10 science beakons to get the first researched tech etc.
Techs gained from huts, on the other-hand, do seem to slow down research rates, as do normal researched technologies.

the availability of techs follows two rules working in combination to each other:

1. the first rule is an xxo pattern. this means, as far as you have the prerequisites, a tech is available, then available, then not available...then availble, then abailable, then not available etc...
each tech starts on a different position of this pattern. they can be xxo, xox or oxx. in order to define this position each tech will get a value. the value can be 0 (xxo), 1(xox) or 2(oxx)

I´m not a programmer, but the algorithm should about look like this:

if (1+n+v-s)/3 = INT then tech is not available

n is the number of techs you have found by then.
v is the value that describes the position in the pattern. as far as I´ve found out them I prepared a table showing the tech-values.
s is the number of starting techs.

2. for understanding the second rule take a look at the rules.txt. you can see that all techs are listed in alphabetical order there. the highest ranked tech is Advanced Flight, followed by Alphabet, then Amphibious Warfare etc.
the highest ranked available tech in the rules.txt acts as a joker tech. it is always available and doesn´t follow the xxo pattern. since Advanced Flight isn´t available in the beginning, Alphabet will be the first joker tech. when you discover Alphabet, another tech will become a joker tech (for example Bronze).
When you have the prerequisites for a tech which is ranked higher in the rules.txt than the current joker tech, the new tech will take its place. the former joker tech will follow the xxo pattern as described above. (example: Bronze is joker tech, after detecting Mysticism and Mathmatics Astronomy will become available as new joker tech. from now on Bronze will follow the usual xxo pattern).

I prepared a table with an example path showing the available and the missing techs for choose. the numbers in the brackets describe the values of the techs. I think when you take a look at it you will understand the rule.

techs from huts or from other civs (by stealing, trading or GL) behave like regulary discovered techs.
(example: after detecting alpha and cer. burial you notice that you can´t choose law code from the table. you decide for pottery for whatever reason. in the same turn you find writing under a hut, later you conquer a Mongolian city getting Warrior Code. if you don´t get any other tech before discovering Pottery you won´t be able to choose Law Code again.)
starting techs, however, behave like never researched techs. that´s why they play into the formula above.

well, this is the rule as far as I was able to describe it. now see what you can do with it

Awsome!!

------------------
____________
Scouse Git[1]

So the designers used this as a way to prevent certain fast track tech paths. Good planning. But it seems that there should be no problem with Pottery (1), Map Making (2), Seafaring (0) if you timed it right. A Pottery, Alphabet, Map Making, Seafaring tech tree should work just fine.

*Goes and tests this hypothesis*

It worked! Seafaring was the fourth tech I recieved.

But you said in the other thread that "map making->pottery->seafaring" does not work. Hmm... Maybe this means that if you start with a tech, it doesn't affect the pattern.

So, the unavailable techs will be Map Making (2), Pottery (1), Seafaring (0). So if you start with Alphabet, you can't get Seafaring as the third tech. But if you don't start with it and have to research it, you will be fine.

Anyway, It would appear pretty obvious to me that if you take this formula and include Richard's observations, it would appear that all techs of a particular type (war, econ, etc) very well could have the same assigned number (0,1 or 2).

For my third and final note I just have to say that all of the recent statistical analysis of civ is pretty exciting for me. I am a programmer by trade but a statistician at heart. I never dreamed of doing such work on the game but now I find myself constantly trying to think of other areas of the game to analyze.

If you can't tell, that is a compliment. I have always wondered why Techs disappear and appear when they do. Thanks.

Congratulations again.

Just for fun, I compared your "oedo value" to the position of each tech in the rules.txt list. There seems to be a definite pattern there.

All of the techs in your table repeated a 2, 1, 0 pattern starting with Alphabet. In other words, Bridge Building, Bronze Working and Ceremonial Burial, the 8th, 9th and 10th techs in the list, have "oedo values" of 2, 1 and 0, in that order. Theology, Theory of Gravity and Trade, the 83rd, 84th and 85th techs, also repeat. The only exception is Chemistry. You gave it a value of 0, its position in the table would indicate a value of 2. (0 must be an typo since 2 happens to be the value for Chemistry in your example path.)

If this pattern holds for the as yet undiscovered techs, a simplification of your basic formula may be possible. Every time a tech can be researched, one third of them are effectively taken off the complete list of techs. Next research time those techs are put back on and another third is taken off the list. On the first research event, the 2nd (Alphabet, made available by the joker phenomenon), 5th, 8th, etc, techs are taken out of the available list. In the second research event, the 3rd, 6th, 9th (Bronze Working), etc, are taken out of the list. In the third research event, the 1st, 4th, 7th, 10th (Ceremonial Burial), etc, are taken out of the list. This pattern should then repeat.

This also explains why it is impossible to get Monarchy in four tries without free techs or huts. Both prerequisites, Ceremonial Burial and Code of Laws, are removed from the list on the third research event!!!

What do you think?

I think Sequoya is probably right, that the formula is just based on position in rules.txt. Here's a list of the techs, each marked with the turn when it's not available. Take the number of techs you've discovered, divide by 3, and take the remainder (modulus, for fellow programmer types). Any tech marked with that number in the following table is not available for research.

This is obviously implemented for better game balance, because, as suas333 pointed out, it prevents one civ to be too specialized in one particular branch of the tech tree and ignore development in other areas altogether. However, the way the pattern is determines sees to be random (i.e. based on alphabetical order rather than, say, tech category). So I wonder if it could cause some anomaly, such as the one raised in the question "Why is Warrior Code bad?". But I guess if the pool of techs is big enough, the chance for that to happen is rather small. Beisdes, if this pattern is correct, once you have obtained the pre-reqs for a particular tech, it will only stay out of the choice menu once among three advance times.

I am very interested in this topic because I am considering if this should be implemented in Freeciv. One of problems with Freeciv gameplay is that tech development is too fast and unbalanced. Another big problem is that expansion is way too easy -- nobody bothers with city development at all. I think a higher degree of unhappiness, like in the Deity level of Civ2, will address the problem by slowing the game down, but it seems no one would listen. People are just too set in their ways, I guess.

There is possibly more to this. We have all heard tales of techs that disappear for a long time (like Flight or occasionally Trade). With the proposed solution, techs would only be unavailble for one research turn. Maybe certain techs are just rarer, or maybe the pattern changes after you have reached a certain number of techs. The beaker cost for techs follows a regular progression and then takes a big jump at the 20th tech. The same thing could happen with the unavailable tech list.

------------------
Go Redskins!

_ = not available or already discovered
a = available
* = researched
o = should be available, but is not
# = last digit of number of techs discovered

------------------
____________
Scouse Git[1]

Paul will confirm that some OCC tables disprooved my xxxo theory at first. but it turned out it wasn´t a program error. the years were simply wrong recorded. on the other hand, we all know that civ2 is pretty buggy

Merc, the OCC path was expounded by Paul on one of these threads. Strongly suspect there are no gaps in availability in his proposed approach.