Merge potential next release v0.4 (#187) Breaking Changes

* First draft of the new n-dimensional arrays + NB use case
* Improves default implementation of multiple Array methods
* Refactors tree methods
* Adds matrix decomposition routines
* Adds matrix decomposition methods to ndarray and nalgebra bindings
* Refactoring + linear regression now uses array2
* Ridge & Linear regression
* LBFGS optimizer & logistic regression
* LBFGS optimizer & logistic regression
* Changes linear methods, metrics and model selection methods to new n-dimensional arrays
* Switches KNN and clustering algorithms to new n-d array layer
* Refactors distance metrics
* Optimizes knn and clustering methods
* Refactors metrics module
* Switches decomposition methods to n-dimensional arrays
* Linalg refactoring - cleanup rng merge (#172)
* Remove legacy DenseMatrix and BaseMatrix implementation. Port the new Number, FloatNumber and Array implementation into module structure.
* Exclude AUC metrics. Needs reimplementation
* Improve developers walkthrough

New traits system in place at `src/numbers` and `src/linalg`
Co-authored-by: Lorenzo <tunedconsulting@gmail.com>

* Provide SupervisedEstimator with a constructor to avoid explicit dynamical box allocation in 'cross_validate' and 'cross_validate_predict' as required by the use of 'dyn' as per Rust 2021
* Implement getters to use as_ref() in src/neighbors
* Implement getters to use as_ref() in src/naive_bayes
* Implement getters to use as_ref() in src/linear
* Add Clone to src/naive_bayes
* Change signature for cross_validate and other model_selection functions to abide to use of dyn in Rust 2021
* Implement ndarray-bindings. Remove FloatNumber from implementations
* Drop nalgebra-bindings support (as decided in conf-call to go for ndarray)
* Remove benches. Benches will have their own repo at smartcore-benches
* Implement SVC
* Implement SVC serialization. Move search parameters in dedicated module
* Implement SVR. Definitely too slow
* Fix compilation issues for wasm (#202)

Co-authored-by: Luis Moreno <morenol@users.noreply.github.com>
* Fix tests (#203)

* Port linalg/traits/stats.rs
* Improve methods naming
* Improve Display for DenseMatrix

Co-authored-by: Montana Low <montanalow@users.noreply.github.com>
Co-authored-by: VolodymyrOrlov <volodymyr.orlov@gmail.com>

src/numbers/floatnum.rs

@@ -0,0 +1,117 @@
+use rand::Rng;
+
+use num_traits::{Float, Signed};
+
+use crate::numbers::basenum::Number;
+
+/// Defines float number
+/// <script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.0/MathJax.js?config=TeX-AMS_CHTML"></script>
+pub trait FloatNumber: Number + Float + Signed {
+    /// Copy sign from `sign` - another real number
+    fn copysign(self, sign: Self) -> Self;
+
+    /// Calculates natural \\( \ln(1+e^x) \\) without overflow.
+    fn ln_1pe(self) -> Self;
+
+    /// Efficient implementation of Sigmoid function, \\( S(x) = \frac{1}{1 + e^{-x}} \\), see [Sigmoid function](https://en.wikipedia.org/wiki/Sigmoid_function)
+    fn sigmoid(self) -> Self;
+
+    /// Returns pseudorandom number between 0 and 1
+    fn rand() -> Self;
+
+    /// Returns 2
+    fn two() -> Self;
+
+    /// Returns .5
+    fn half() -> Self;
+
+    /// Returns \\( x^2 \\)
+    fn square(self) -> Self {
+        self * self
+    }
+
+    /// Raw transmutation to u64
+    fn to_f32_bits(self) -> u32;
+}
+
+impl FloatNumber for f64 {
+    fn copysign(self, sign: Self) -> Self {
+        self.copysign(sign)
+    }
+
+    fn ln_1pe(self) -> f64 {
+        if self > 15. {
+            self
+        } else {
+            self.exp().ln_1p()
+        }
+    }
+
+    fn sigmoid(self) -> f64 {
+        if self < -40. {
+            0.
+        } else if self > 40. {
+            1.
+        } else {
+            1. / (1. + f64::exp(-self))
+        }
+    }
+
+    fn rand() -> f64 {
+        let mut rng = rand::thread_rng();
+        rng.gen()
+    }
+
+    fn two() -> Self {
+        2f64
+    }
+
+    fn half() -> Self {
+        0.5f64
+    }
+
+    fn to_f32_bits(self) -> u32 {
+        self.to_bits() as u32
+    }
+}
+
+impl FloatNumber for f32 {
+    fn copysign(self, sign: Self) -> Self {
+        self.copysign(sign)
+    }
+
+    fn ln_1pe(self) -> f32 {
+        if self > 15. {
+            self
+        } else {
+            self.exp().ln_1p()
+        }
+    }
+
+    fn sigmoid(self) -> f32 {
+        if self < -40. {
+            0.
+        } else if self > 40. {
+            1.
+        } else {
+            1. / (1. + f32::exp(-self))
+        }
+    }
+
+    fn rand() -> f32 {
+        let mut rng = rand::thread_rng();
+        rng.gen()
+    }
+
+    fn two() -> Self {
+        2f32
+    }
+
+    fn half() -> Self {
+        0.5f32
+    }
+
+    fn to_f32_bits(self) -> u32 {
+        self.to_bits()
+    }
+}