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| </pre><pre class="rust"><code><span class="doccomment">//! Utility functions for random functionality. |
| //! |
| //! This module provides sampling and shuffling which are used |
| //! within the learning modules. |
| |
| </span><span class="kw">use </span>rand::{Rng, thread_rng}; |
| |
| <span class="doccomment">/// ``` |
| /// use rusty_machine::learning::toolkit::rand_utils; |
| /// |
| /// let mut pool = &mut [1,2,3,4]; |
| /// let sample = rand_utils::reservoir_sample(pool, 3); |
| /// |
| /// println!("{:?}", sample); |
| /// ``` |
| </span><span class="kw">pub fn </span>reservoir_sample<T: Copy>(pool: <span class="kw-2">&</span>[T], reservoir_size: usize) -> Vec<T> { |
| <span class="macro">assert!</span>(pool.len() >= reservoir_size, |
| <span class="string">"Sample size is greater than total."</span>); |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>pool_mut = <span class="kw-2">&</span>pool[..]; |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>res = pool_mut[..reservoir_size].to_vec(); |
| pool_mut = <span class="kw-2">&</span>pool_mut[reservoir_size..]; |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>ele_seen = reservoir_size; |
| <span class="kw">let </span><span class="kw-2">mut </span>rng = thread_rng(); |
| |
| <span class="kw">while </span>!pool_mut.is_empty() { |
| ele_seen += <span class="number">1</span>; |
| <span class="kw">let </span>r = rng.gen_range(<span class="number">0</span>..ele_seen); |
| |
| <span class="kw">let </span>p_0 = pool_mut[<span class="number">0</span>]; |
| pool_mut = <span class="kw-2">&</span>pool_mut[<span class="number">1</span>..]; |
| |
| <span class="kw">if </span>r < reservoir_size { |
| res[r] = p_0; |
| } |
| } |
| |
| res |
| } |
| |
| <span class="doccomment">/// The inside out Fisher-Yates algorithm. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use rusty_machine::learning::toolkit::rand_utils; |
| /// |
| /// // Collect the numbers 0..5 |
| /// let a = (0..5).collect::<Vec<_>>(); |
| /// |
| /// // Perform a Fisher-Yates shuffle to get a random permutation |
| /// let permutation = rand_utils::fisher_yates(&a); |
| /// ``` |
| </span><span class="kw">pub fn </span>fisher_yates<T: Copy>(arr: <span class="kw-2">&</span>[T]) -> Vec<T> { |
| <span class="kw">let </span>n = arr.len(); |
| <span class="kw">let </span><span class="kw-2">mut </span>rng = thread_rng(); |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>shuffled_arr = Vec::with_capacity(n); |
| |
| <span class="kw">unsafe </span>{ |
| <span class="comment">// We set the length here |
| // We only access data which has been initialized in the algorithm |
| </span>shuffled_arr.set_len(n); |
| } |
| |
| <span class="kw">for </span>i <span class="kw">in </span><span class="number">0</span>..n { |
| <span class="kw">let </span>j = rng.gen_range(<span class="number">0</span>..i + <span class="number">1</span>); |
| |
| <span class="comment">// If j isn't the last point in the active shuffled array |
| </span><span class="kw">if </span>j != i { |
| <span class="comment">// Copy value at position j to the end of the shuffled array |
| // This is safe as we only read initialized data (j < i) |
| </span><span class="kw">let </span>x = shuffled_arr[j]; |
| shuffled_arr[i] = x; |
| } |
| |
| <span class="comment">// Place value at end of active array into shuffled array |
| </span>shuffled_arr[j] = arr[i]; |
| } |
| |
| shuffled_arr |
| } |
| |
| <span class="doccomment">/// The in place Fisher-Yates shuffle. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use rusty_machine::learning::toolkit::rand_utils; |
| /// |
| /// // Collect the numbers 0..5 |
| /// let mut a = (0..5).collect::<Vec<_>>(); |
| /// |
| /// // Permute the values in place with Fisher-Yates |
| /// rand_utils::in_place_fisher_yates(&mut a); |
| /// ``` |
| </span><span class="kw">pub fn </span>in_place_fisher_yates<T>(arr: <span class="kw-2">&mut </span>[T]) { |
| <span class="kw">let </span>n = arr.len(); |
| <span class="kw">let </span><span class="kw-2">mut </span>rng = thread_rng(); |
| |
| <span class="kw">for </span>i <span class="kw">in </span><span class="number">0</span>..n { |
| <span class="comment">// Swap i with a random point after it |
| </span><span class="kw">let </span>j = rng.gen_range(<span class="number">0</span>..n - i); |
| arr.swap(i, i + j); |
| } |
| } |
| |
| <span class="attribute">#[cfg(test)] |
| </span><span class="kw">mod </span>tests { |
| <span class="kw">use super</span>::<span class="kw-2">*</span>; |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>test_reservoir_sample() { |
| <span class="kw">let </span>a = <span class="macro">vec!</span>[<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">4</span>, <span class="number">5</span>, <span class="number">6</span>, <span class="number">7</span>]; |
| |
| <span class="kw">let </span>b = reservoir_sample(<span class="kw-2">&</span>a, <span class="number">3</span>); |
| |
| <span class="macro">assert_eq!</span>(b.len(), <span class="number">3</span>); |
| } |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>test_fisher_yates() { |
| <span class="kw">let </span>a = (<span class="number">0</span>..<span class="number">10</span>).collect::<Vec<<span class="kw">_</span>>>(); |
| |
| <span class="kw">let </span>b = fisher_yates(<span class="kw-2">&</span>a); |
| |
| <span class="kw">for </span>val <span class="kw">in </span>a.iter() { |
| <span class="macro">assert!</span>(b.contains(val)); |
| } |
| } |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>test_in_place_fisher_yates() { |
| <span class="kw">let </span><span class="kw-2">mut </span>a = (<span class="number">0</span>..<span class="number">10</span>).collect::<Vec<<span class="kw">_</span>>>(); |
| |
| in_place_fisher_yates(<span class="kw-2">&mut </span>a); |
| |
| <span class="kw">for </span>val <span class="kw">in </span><span class="number">0</span>..<span class="number">10 </span>{ |
| <span class="macro">assert!</span>(a.contains(<span class="kw-2">&</span>val)); |
| } |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../../../" data-current-crate="rusty_machine" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
