modified: docs/estimating_frequencies_from_small_samples.md
modified: docs/libraries/cpp_automatic_memory_management.md modified: docs/libraries/time.md modified: docs/manifesto/consensus.md renamed: docs/notes/big_cirle_notation.md -> docs/notes/big_circle_notation.md modified: docs/writing_and_editing_documentation.md
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docs/design/mkdocs.sh
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docs/design/mkdocs.sh
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@ -317,6 +317,25 @@ cases this is not going to be the cases, for a real is usually going to have som
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finite distribution, and thus it is more likely to be OK to use the uncorrected
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delta distribution
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## Haldane prior $α=0$ $β=0$
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This is a pathological and unusable prior, because $B(0,0)$ is infinite.
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We cannot actually do anything with it, but has the desirable characteristic
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that almost none or almost all are highly weighted, giving us much the same result as above.
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It presupposes that we truly know nothing, but one has to start with some ground under one's feet.
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One must always start with some leap of faith.
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Since it is unusable, one may take $α=ɛ$, $β=ɛ$ where $ɛ$ is some small quantity, the smaller $ɛ$ is,
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the smaller one's initial leap of faith If small, gives us a reasonable result for "all men are mortal".
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Maybe immortals exist, but are enormously rare, and a small number of samples, assuming this prior,
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gives us confidence that immortal men are extremely rare, but still predicts only very rare, not nonexistent.
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$ɛ = \frac{1}{2}$ is a prior that generally gives results that are not too silly,
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and avoids the complexity of our dual distribution delta function.
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On the other hand, our dual distribution just gives us saner and more commonsensical conclusions.
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## the metalog (metalogistic) distribution
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The metalogistic distribution is like the Beta distribution in that
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@ -326,25 +345,30 @@ as many terms as are required for the nature of the thing being represented.
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The Beta distribution plus two delta functions is a metalogistic distribution
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if we stretch the definition of the metalogistic distribution slightly.
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The Beta distribution represents the probability of a probability
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(since we are using it for its Bayesian update capability).
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For example we have a collection of urns containing red and blue balls,
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For example we have a collection of urns containing red and not red balls,
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and from time to time we draw a ball out of an urn and replace it,
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whereupon the Beta distribution is our best guess
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about the likelihood that it contains a certain ratio of red and blue balls
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about the likelihood that it contains a certain ratio of red and not red balls
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(also assuming the urns are enormously large,
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and also always contain at least some red and at least some blue balls)
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and also always contain at least some red and at least some not red balls)
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Suppose, however, the jars contain gravel, the size of each piece
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of gravel in a jar being normally distributed, and we want to
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estimate the size and standard deviation of the gravel in an urn,
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rather than the ratio of red balls and blue balls.
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rather than the ratio of red balls and not balls.
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(Well, the size $s$ cannot be normally distributed, because $s$ is strictly non negative, but perhaps $\ln(s)$, or $s\ln(s)$, or $(s/a -a/s)$ is normally distributed.)
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(Well, the size $s$ cannot be normally distributed, because $s$ is strictly non negative,
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but perhaps $\ln(s)$, or $s\ln(s)$, or $(s/a -a/s)$ is normally distributed., or
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perhaps we should assume a poisson distributon.)
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Whereupon our Baysian updates become more complex,
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and our prior has to contain difficult to justify information
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(no boulders or dust in the urns), but we are still doing Bayesian updates,
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hence the Beta distribution, and its generalization
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hence the Beta distribution, or rather its generalization
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the metalogistic distribution, still applies.
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Typically we want to exclude outliers as evidence, so we assume
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a metalogistic distribution that is the sum of two terms, one
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narrowly distributed, and one broadly distributed with a long tail.
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@ -2,7 +2,9 @@
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title:
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C++ Automatic Memory Management
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...
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# Memory Safety
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Modern, mostly memory safe C++, is enforced by:\
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- Microsoft safety checker
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@ -151,7 +153,7 @@ objects that reference resources, primarily unique_pointer.
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`std::move(t)` is equivalent to `static_cast<decltype(t)&&>(t)`, causing move
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semantics to be generated by the compiler.
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`t`, the compiler assumes is converted by your move constructor or move assignment into a valid state where your destructor will not need to anything very costly.
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`t`, the compiler assumes, is converted by your move constructor or move assignment into a valid state where your destructor will not need to anything very costly.
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`std::forward(t)` causes move semantics to be invoked iff the thing referenced
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is an rvalue, typically a compiler generated temporary, *conditionally*
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@ -348,41 +350,11 @@ use with placement new
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pmc->~MyClass(); //Explicit call to destructor.
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aligned_free(p);.
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# GSL: Guideline Support Library
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# spans
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The Guideline Support Library (GSL) contains functions and types that
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are suggested for use by the C++ Core Guidelines maintained by the
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Standard C++ Foundation. This repo contains [Microsoft’s implementation
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of GSL](https://github.com/Microsoft/GSL).
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A span is a non owning pointer and count.
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git clone https://github.com/Microsoft/GSL.git
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cd gsl
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git tag
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git checkout tags/v2.0.0
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Which implementation mostly works on gcc/Linux, but is canonical on
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Visual Studio.
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For usage of spans ([the replacement for bare naked non owning pointers
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subject to pointer
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arithmetic)](http://codexpert.ro/blog/2016/03/07/guidelines-support-library-review-spant/)
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For usage of string spans ([String
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spans](http://codexpert.ro/blog/2016/03/21/guidelines-support-library-review-string_span/)
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These are pointers to char arrays. There does not seem to be a UTF‑8
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string_span.
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GSL is a preview of C++20, as boost contained a preview of C++11.
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It is disturbingly lacking in official documentation, perhaps because
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still subject to change.
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[Unofficial
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documentation](http://modernescpp.com/index.php/c-core-guideline-the-guidelines-support-library)
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It provides an optional fix for C’s memory management problems, while
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still retaining backward compatibility to the existing pile of rusty
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razor blades and broken glass.
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It would perhaps be more useful if we also hand owning pointers with counts
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# The Curiously Recurring Template Pattern
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@ -456,85 +428,54 @@ named functor class.
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To construct a lambda in the heap:
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```c++
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auto p = new auto([a,b,c](){})
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auto q = new auto([](int x) { return x * x; });
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int result = (*q)(5); // Calls the lambda with the argument 5
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delete p;
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delete q;
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```
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Objects inside the lambda are constructed in the heap.
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But if you have pointers to lambdas, std::function is more useful than lambda, because then you can declare their pointer type.
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If you want to declare a pointer type that can point to any lambda with the same signature, or indeed any instance of
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a class that supports operator(), you can use std::function:
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```C++
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#include <functional>
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// Declare a pointer to a lambda that takes an int and returns an int
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std::function<int(int)>* lambdaPtr = new std::function<int(int)>([](int x) { return x * x; });
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// Use the lambda
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int result = (*lambdaPtr)(5);
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// Clean up
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delete lambdaPtr;
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```
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This way, lambdaPtr is a pointer to a std::function that can store any callable object, including lambdas, that take an int and return an int.
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similarly placement `new`, and `unique_ptr`.
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To template a function that takes a lambda argument:
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## callbacks
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template <typename F>
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void myFunction(F&& lambda){
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//some things
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In C, a callback is implemented as an ordinary function pointer, and a pointer to void, which is then cast to a data
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structure of the desired type.
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You can put a lambda in a class using decltype,and pass it around for
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continuations, though you would probably need to template the class:
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What the heavy C++ machinery of `std::function` does is bind the two together.
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template<class T>class foo {
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public:
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T func;
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foo(T in) :func{ in } {}
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auto test(int x) { return func(x); }
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};
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....
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auto bar = [](int x)->int {return x + 1; };
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foo<(bar)>foobar(bar);
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Sometimes you want to have indefinitely many data structures, which are dynamically allocated
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and then discarded.
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But we had to introduce a name, bar, so that decltype would have
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something to work with, which lambdas are intended to avoid. If we are
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going to have to introduce a compile time name, easier to do it as an
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old fashioned function, method, or functor, as a method of a class that
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is very possibly pod.
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Sometimes you want to have a single data structure that gets overwritten frequently. The latter is
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preferable when it suffices, since it means that asynch callback code is more like sync code.
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If we are sticking a lambda around to be called later, might copy
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it by value into a templated class, or might put it on the heap.
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In one case, you would allocate the object every time, and when does with it, discard it.
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auto bar = []() {return 5;};
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You can give it to a std::function:
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auto func_bar = std::function<int()>(bar);
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In this case, it will get a copy of the value of bar. If bar had
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captured anything by value, there would be two copies of those values on
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the stack; one in bar, and one in func_bar.
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When the current scope ends, func_bar will be destroyed, followed by
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bar, as per the rules of cleaning up stack variables.
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You could just as easily allocate one on the heap:
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auto bar_ptr = std::make_unique(bar);
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std::function <int(int)> increm{[](int arg{return arg+1;}}
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presumably does this behind the scenes
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On reflection we could probably use this method to produce a
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templated function that stored a lambda somewhere in a templated class
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derived from a virtual base class for execution when the event triggered
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by the method fired, and returned a hashcode to the templated object for
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the event to use when the event fired. The event gets the event handler
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from the hashcode, and the virtual base class in the event handler fires
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the lambda in the derived class, and the lambda works as a continuation,
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operating in the context wherein it was defined, making event oriented
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programming almost as intuitive as procedural programming.
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But then we have a problem, because we would like to store event
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handlers in the database, and restore them when program restarts, which
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requires pod event handlers, or event handlers constructible from POD
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data, which a lambda is not.
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We could always have some event handlers which are inherently not POD
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and are never sent to a database, while other event handlers are, but
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this violates the dry design principle. To do full on functional
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programming, use std::function and std::bind, which can encapsulate
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lambdas and functors, but are slow because of dynamic allocation
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C++ does not play well with functional programming. Most of the time you
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can do what you want with lambdas and functors, using a pod class that
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defines `operator(...)`
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In the other case it would be a member variable of struct that hangs around and is continually
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re-used.
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# auto and decltype(variable)
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@ -553,7 +494,7 @@ procedurally, as by defining a lambda, but by defining a derived type.
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# Variable length Data Structures
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C++ just does not handle them well, except you embed a vector in them,
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C++ just does not handle them well, except you embed an `std::vector` in them,
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which can result in messy reallocations.
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One way is to drop back into old style C, and tell C++ not to fuck
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@ -576,9 +517,6 @@ around.
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return output;
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}
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Another solution is to work around C++’s inability to handle variable
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sized objects by fixing your hash function to handle disconnected data.
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# for_each
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template<class InputIterator, class Function>
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docs/libraries/mkdocs.sh
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docs/libraries/mkdocs.sh
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title: time
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sidebar: true
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notmine: false
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...
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abstract: >-
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We plan to have a network with all parties agreeing on the consensus network time,
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which accommodates leap seconds by being rubbery,
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passing at 1001 milliseconds per second, or 999 milliseconds per second, or so,
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when a leap second happens.
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peers running on linux systems that claim their tai time is accurate should
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stubbornly steer the consensus time to the tai time, but not too stubbornly
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because they can have a wrong tai time.
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---
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the C++ library chrono reports the steady time, guaranteed not to jump,
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# timekeeping primitives
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[chrono]:https://en.cppreference.com/w/cpp/chrono {target="_blank"}
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the C++ library [chrono] reports the steady time, guaranteed not to jump,
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and guaranteed to pass at very very close to one second per actual second,
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but not guaranteed to have any particular relationship with any other machine,
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and also the global official time, with no guarantees
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that it is not wildly wrong, and which once in a while jumps by a second.
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the global official time, the system time, with no guarantees
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that it is not wildly wrong, and which once in a while jumps by a second,
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and, on C++20, the tai time, guaranteed to not jump.
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To check the global posix time on linux, *and uncertainty in that time* on linux
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However there are linux specific calls that report the system time,
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the global posix time on linux, *and uncertainty in that time*.
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``` c
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#include <stdio.h>
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@ -39,6 +45,8 @@ int main()
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}
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```
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# ad hoc consensus time
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Those machines that do not have an accurate global time will try to be
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at the median of all the machines that they have direct connection with
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while biasing the consensus towards the passage of one second per second,
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@ -50,12 +58,14 @@ they will stubbornly drag their heels in moving to the new consensus.
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Those that do have an accurate global time will try to be nearer to the
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global time, while remaining inside two thirds of the distribution.
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If the network
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time differs by so from the authoritative time, they will be as
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close as they can be to the authoritative time, while remaining inside
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time differs by so from the authoritative tai time, they will be as
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close as they can be to the authoritative tai time, while remaining inside
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the majority consensus, thus causing the consensus to drift towards
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the authoritative time.
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the authoritative tai time.
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This describes an ad hoc mechanism for keeping consensus.
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# Bayesian consensus
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(People agree on metalog distribution of consensus time)
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[gamma distribution]:../estimating_frequencies_from_small_samples.html#beta-distribution
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{target="_blank"}
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@ -73,3 +83,10 @@ Or cleverer still and accommodate leap seconds by consensus
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on both the time and the rate of passage of consensus time relative
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to steady time by a [delta distribution], in which case we have
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a three dimensional $α$ and $β$
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But both distributions suffer from the pathology that outliers will have
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large effect, when they should have little effect.
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So we need a metalog distribution that represents the sum of two
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distributions, one narrow, and one wide and long tailed.
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So outliers affect primarily the long tailed distribution
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sidebar: true
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notmine: false
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abstract: >-
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Consensus is a hard problem, and gets harder when you have shards
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consensus is a hard problem, and considerably harder when you have shards
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Nakomoto Satoshi's implementation of Nakomoto consensus, aptly described
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as wading through molasses, failed to scale
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---
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# Failure of Bitcoin consensus to scale
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Mining pools, asics
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# Monero consensus
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RandomX prevented asics, because RandomX mining is best done on a general purpose CPU,
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but as Monero got bigger, it came to pass that payouts got bigger. And because
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more and more people were trying to mine a block, they got rarer and rarer
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So miners joined in mining pools, so as to get smaller, but more regular and
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predicable payouts more often. Which destroys the decentralization objective
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of mining, giving the central authority running the mining pool dangerously great
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power over the blockchain.
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Monero's workaround for this is P2Pool, a mining pool without centralization.
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But not everyone wants to use P2Pool.
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Monero has a big problem with people preferring to mine in big pools, because
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of the convenience provided by the dangerously powerful central authority.
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It easier for the individual miner to let the center make all the decisions that
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matter, but many of these decisions matter to other people, and the center could
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make decisions that are contrary to everyone else's interests. Even if the
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individual miner is better off than mining solo, this could well make everyone
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including the individual miner worse off, because he and everyone may be
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adversely affected by other people's decision to pool mine.
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0
docs/manifesto/mkdocs.sh
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docs/manifesto/mkdocs.sh
Normal file → Executable file
0
docs/mkdocs.sh
Normal file → Executable file
0
docs/mkdocs.sh
Normal file → Executable file
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docs/names/mkdocs.sh
Normal file → Executable file
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docs/names/mkdocs.sh
Normal file → Executable file
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docs/notes/mkdocs.sh
Normal file → Executable file
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docs/notes/mkdocs.sh
Normal file → Executable file
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docs/rootDocs/mkdocs.sh
Normal file → Executable file
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docs/rootDocs/mkdocs.sh
Normal file → Executable file
0
docs/setup/mkdocs.sh
Normal file → Executable file
0
docs/setup/mkdocs.sh
Normal file → Executable file
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