Hundred's of deck in Anki: why it can be useful
I am going to try to explain why I do have hundreds of deck and subdecks. Furtheromer, why I believe there is currently no better way to achieve my goal with anky. The best way to use anki is to use.
I first review the due cards. For those very card, I would certainly love to use varied practice and see every cards at random. Edit: I just discovered that this can be done using a filtered deck with search tag «is due».
Indeed, every single decks are subdecks of one deck, called "A", so that I don't have to select a deck after another when I begin to review my cards. Here, I would love to use varied practice, and have every review cards mixed. I recall reading that this feature will exists in a future version of anki. I don't know when. As far as I know, there is no add-on for it, and anyway an add-on would not be helpful to review those cards on ankidroid.
Once due cards are done, I move to new cards. Here is the beginning of the reason I need a lot of decks. I know that I can see 200 new cards by day without too much trouble. This is indeed what I have done for months. But I certainly can NOT see 200 new cards of one subject. Because the knowledge which interests me is a stack. You need to have good foundation to learn advanced stuff. Let me give you an example, you don't need to understand mathematics to understand the example.
In my «algebra::ring» deck, I have a note with the definition of «the augmentation ideal of RG, for R a ring and G a group». The definition is «the kernel of RG by its augmentation map». This means that, before learning this card, I certainly have to understand what is a group, a ring, an ideal, RG, a map, the augmentation map of RG, and the kernel of a ring by a map. For this very reason, new cards are seen in the order in which they were added in the deck, and not in ranodm order. Each of those notion are really simple to understand independtly. My trouble was only that they were too many notions. I was not able to have all of them in my head at the same time. Therefore, I must advance slowly in this deck, not seeing more than one or two new cards by day. And when there are no new card in the deck anymore, adding only a section or two of the Algebra book in Anki. No more, otherwise I would not understand what I am writting.
But, while I take my time to learn ring theory, I can certainly learn new thing in group theory, in analysis, in python, in automata theory, and in a hundred of other subjects (litterally), even some which are less close from my studies/job. But, in order to let Anki knows which card belong to which subject, whether a card is physics, analysis, group theory, ring theory, guitar or cooking, I have to use decks. Using tags would let me know which is which, but would not allow me to precisely ask for one/two card of each subject every day.
In order to give a more concrete example, here is the list of decks which are not subdecks: Algorithm, art, chemistry, computer science, economics, people, hardware, language, logic, mathematics, other, physics, programming, software, everyday life. In Mathematics, the subdecks are Algebra, analysis, category, combinatorics, numbers, geometry, information theory, measure theory, number theory, probability, topology. In the Algebra subdeck, there are: linear algeba, semigroup theory, abstract algebra (Summit-Foote). In this last subsubdeck, there is a subsubsubdeck by part. Group, field, module theory, representation theory, and rings.
 With a few exception. For example I began recently a guitar deck. I certainly want to see this deck only when I do have my guitar with me, and not when I use anki in the subway
 You can download a copy of my profile, minus some personal cards I do not want to share, here. It weight 3,7MO and contains LaTeX code for more than 50 000 formulas. If you try to «check media», it will be VERY LONG !
 And commutative algebra, but there is no new cards, since I lack a lot of definition from the previous parts.