Merge 4771a1b into bad3f55

include/autoppl/distribution/discrete.hpp

@@ -0,0 +1,48 @@
+#pragma once
+#include <cassert>
+#include <random>
+#include <cmath>
+#include <numeric>
+
+namespace ppl {
+
+// TODO: change name to DiscreteDist and make class template.
+// Discrete should be a function that creates this kind of object.
+
+template <typename weight_type>
+struct Discrete 
+{
+    using value_t = int;
+    using dist_value_t = double;
+
+    Discrete(std::initializer_list<weight_type> weights)
+        : weights_{weights} { assert(weights.size() > 0); }
+
+    template <class GeneratorType>
+    value_t sample(GeneratorType& gen) const
+    {
+        std::discrete_distribution dist(weights_.begin(), weights_.end()); 
+        return dist(gen);
+    }
+
+    dist_value_t pdf(value_t i) const
+    {
+        assert( i >= 0 && i < (int) weights_.size() );
+        return weights(i) / std::accumulate(weights_.begin(), weights_.end(), 0.0 );
+
+    } 
+
+    dist_value_t log_pdf(value_t i) const
+    {
+        assert( i >= 0 && i < (int) weights_.size() );
+        return log(weights(i) / std::accumulate(weights_.begin(), weights_.end(), 0.0 ));
+    }
+
+    inline dist_value_t weights(value_t i) const { return static_cast<dist_value_t>(weights_[i]); }
+
+   private:
+    std::vector<weight_type> weights_;
+};
+
+} // namespace ppl
+

test/CMakeLists.txt

@@ -54,6 +54,7 @@ add_executable(dist_expr_unittest
     ${CMAKE_CURRENT_SOURCE_DIR}/expression/distribution/density_unittest.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/expression/distribution/normal_unittest.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/expression/distribution/uniform_unittest.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/distribution/discrete_unittest.cpp
     )
 target_compile_options(dist_expr_unittest PRIVATE -g -Wall -Werror -Wextra)
 target_include_directories(dist_expr_unittest PRIVATE

test/distribution/discrete_unittest.cpp

@@ -0,0 +1,44 @@
+#include <autoppl/distribution/discrete.hpp>
+
+#include <cmath>
+#include <array>
+
+#include "gtest/gtest.h"
+
+namespace ppl {
+namespace dist {
+
+struct discrete_dist_fixture : ::testing::Test {
+protected:
+    std::vector<double> weights {1.0, 2.0, 3.0, 4.0};
+    Discrete<double> dist1 =  {1.0, 2.0, 3.0, 4.0};
+};
+
+TEST_F(discrete_dist_fixture, sanity_Discrete_test) {
+    EXPECT_DOUBLE_EQ(dist1.weights(0), 1.0);
+    EXPECT_DOUBLE_EQ(dist1.weights(1), 2.0);
+    EXPECT_DOUBLE_EQ(dist1.weights(2), 3.0);
+    EXPECT_DOUBLE_EQ(dist1.weights(3), 4.0);
+}
+
+TEST_F(discrete_dist_fixture, simple_Discrete) {
+    EXPECT_DOUBLE_EQ(dist1.pdf(0), dist1.weights(0) / 10.0);
+    EXPECT_DOUBLE_EQ(dist1.pdf(1), dist1.weights(1) / 10.0);
+    EXPECT_DOUBLE_EQ(dist1.pdf(2), dist1.weights(2) / 10.0);
+    EXPECT_DOUBLE_EQ(dist1.pdf(3), dist1.weights(3) / 10.0);
+    // std::accumulate(weights.begin(), weights.end())
+
+}
+
+TEST_F(discrete_dist_fixture, Discrete_sampling) {
+    std::random_device rd{};
+    std::mt19937 gen{rd()};
+
+    for (int i = 0; i < 100; i++) {
+        int sample = dist1.sample(gen);
+        EXPECT_TRUE(sample == 0 || sample == 1 || sample == 2 || sample == 3);
+    }
+}
+
+} // namespace dist
+} // ppl