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The Kindelia Manifesto |
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What is the true nature of computation? A hundred years ago, humanity answered that very question, twice. In 1936, Alan |
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invented the Turing Machine, which, highly inspired by the mechanical trend of the 20th century, distillated the common |
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components of early computers into a single universal machine that, despite its simplicity, was capable of performing |
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every computation conceivable. From simple numerical calculations to entire operating systems, this small machine could |
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do anything. Thanks to its elegance and simplicity, the Turing Machine became the most popular model of computation, and |
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served as the main inspiration behind every modern processor and programming language. C, Fortran, Java, Python are |
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languages based on a procedural mindset, which is highly inspired by Turing's invention. |
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Yet, the Turing Machine wasn't the only model of computation that humanity invented. Albeit a less known history, also |
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in 1936, and in a completely independent way, Alonzo Church invented the Lambda Calculus, which distillated the common |
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components - not of machines, but of different branches of math - into a single universal language that was capable of |
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modeling every mathematical theory. What was surprising, though, is that this language, unexpectedly, could also perform |
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computations. The same algorithms that could be computed by Turing Machines procedurally, could also be computed by the |
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Lambda Calculus, through symbolic manipulations. The idea of using the Lambda Calculus for computations inspired the |
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creation of an entire new branch of programming, which we call the functional paradigm. Haskell, Clojure, Elixir, Agda |
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are languages based on the functional mindset, which is highly inspired by Church's invention. |
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If both Turing Machines (and procedural languages), and the Lambda Calculus (and functional languages), are capable of |
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computation, which mindset is the "right one"? When it comes to raw capabilities, neither. Still on the 20th century, it |
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was proven that, when it comes to computability, Turing Machines and the Lambda Calculus are equivalent. Every problem |
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that one can solve, can also be solved by the other. That insight is known as the Church-Turing thesis, which |
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essentially states that computers are capable of emulating each-other. If that was completely true, then the choice |
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wouldn't matter. After all, if, for example, every programming language is capable of solving the same set of problems, |
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then what is the point in making a choice? |
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Yet, the Church-Turing hypothesis makes a statement about computability, it says nothing about computation. In other |
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words, a model can be inherently less efficient than other. Historically, procedural languages such as C and Fortran, |
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have have consistently outperformed the fastest functional languages, such as Haskell and Ocaml. Yet, languages like |
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Haskell and Agda provide abstractions that make entire classes of bugs unrepresentable. Historically, the functional |
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paradigm has been more secure. |
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The Turing Machine and the Lambda Calculus aren't the only models of computation worth noting, though. In 1983, Stephen |
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Wolfram introduced the Rule 110, an elementary cellular automaton that has been shown to be as capable as both. Wolfram |
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argues that this system is of fundamental importance, and that a new kind of science should emerge from its study. |
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These claims were met with harsh scepticism; after all, if all models are equivalent, what is the point? Yet, we've just |
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stablished that, while equal in capacity, different models result in different practical outcomes. Perhaps there isn't a |
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new branch of science to emerge from the study of alternative models of computation, but what about the design of |
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processors and programming languages? |
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A model of computation has a significant impact on the way we design our languages, and several of their drawbacks can |
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be traced down to limitations of the underlying model. For example, the parallel primitives of the procedural paradigm, |
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mutexes and atomics, provide a contrived, complex solution to multi-threaded synchronization. As a result, parallelism |
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is generally considered hard, and programmers still write sequential code by default. Similarly, security isn't natural |
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to the procedural paradigm. Global state, mutable arrays and loops generate an explosion of possible execution paths, |
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edge cases and off-by-one errors that make absolute security all but impossible. Even highly audited code, such as |
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OpenSSL, is often compromised by out-of-bounds exploits. The functional paradigm handles both issues much better: there |
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is an enourmous amount of inherent parallelism to be extracted from pure functional programs, and logic-based type |
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systems make entire classes of bugs unrepresentable. But if that is the case, then why functional programs are still |
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mostly single-threaded, and bug-ridden? And why isn't the functional paradigm more prevalent? |
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The culprit, we argue, is the underlying model. As much as the Turing Machine, and, thus, the procedural paradigm as a |
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whole, is inadequate for parallelism and security, the Lambda Calculus, and the functional paradigm as a whole, is |
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inadequate for real-world computations. The fundamental operation of the Lambda Calculus, substitution, may trigger an |
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unbounded amount of copies of an unboundedly large argument. Because of that, it can not be performed in a bounded |
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amount of steps, and, thus, there isn't a physical mapping of substitution to real-world physical processes. In other |
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words, substitution isn't an atomic operation, which prevents us from creating efficient functional processors and |
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runtimes. Attempts to solve the issue only pushed it into other directions, such as the need of shared references, which |
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inhibit parallelism, or garbage collection, which isn't atomic. The failure of the functional paradigm to achieve |
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compatible efficiency impacted its popularity, which, in turn, lead to tools like formal verification to never catch up. |
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This raises the question: is there a model of computation which, like Turing Machine, has a clear physical |
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implementation, yet, like the Lambda Calculus, has a robust logical interpretation? In 1997, Yves Lafont proposed a new |
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alternative, the Interaction Combinators, on which substitution is broken down into 2 fundamental laws: commutation, |
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which creates and copies information, and annihilation, which observes and destroys information. In a sense, this may |
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resemble SKI combinators, but that isn't a good analogy, since SKI combinators still include non-atomic operations: K |
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may erase an unboundedly large structure, and S may copy an unboundedly large structure. The charm, and elegance, of the |
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Interaction Combinators is that its reduction laws are truly atomic: each operation can be completed in a constant |
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amount of steps, and has a clear physical mapping. Not only that, they're inherently parallel, in the same sense that |
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the Lambda Calculus has been claimed to be, in theory, but without the issues that let it to be, in practice. |
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Interestingly, every aspect which is considered good in other models of computation is present on Interaction |
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Combinators, while negative aspects are completely absent. Like the Turing Machine, there is a very clear physical |
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implementation. Like the Lambda Calculus, there is a robust logical interpretation which is well-suited for high order |
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abstractions, strong types, formal verification and so on. Curiously, both the Lambda Calculus and the Turing Machine |
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can be emulated by a small Interaction Combinator, with no loss of performance, while the opposite isn't true. This |
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suggests that, while the 3 systems are equivalent in terms of computability, the Interaction Combinators are more |
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capable in terms of computation. Under certain point of view, one could argue that both the Turing Machine and the |
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Lambda Calculus are slight distortions of this fundamental model, with a touch of human creativity, caused by our |
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historical intuitions regarding machines and mathematics, which is the source of their inefficiencies. Perhaps machines |
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and substitutions aren't as fundamental as we think, and some alien civilization has developed all its mathematical |
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theories and computers based on annihilation and commutation, with no references to the Lambda Calculus, or the Turing |
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Machine. |
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We, at the Kindelia Foundation, hold the view that Interaction Combinators are a more fundamental model of computation, |
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and, consequently, that computers, processors and programming languages inspired by them would offer tangible benefits |
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compared to the ones we built based on Turing Machines and the Lambda Calculus. The Kindelia Foundation was created to |
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research this new model of computation, and, through the different mindset it brings, catch insights that will let us |
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produce groundbreaking technology that will push humanity towards the next level of computational maturity. |
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