Added multichannel PReLU

NAM/activations.cpp

@@ -6,6 +6,7 @@ nam::activations::ActivationHardTanh _HARD_TANH = nam::activations::ActivationHa
 nam::activations::ActivationReLU _RELU = nam::activations::ActivationReLU();
 nam::activations::ActivationLeakyReLU _LEAKY_RELU =
   nam::activations::ActivationLeakyReLU(0.01); // FIXME does not parameterize LeakyReLU
+nam::activations::ActivationPReLU _PRELU = nam::activations::ActivationPReLU(0.01); // Same as leaky ReLU by default
 nam::activations::ActivationSigmoid _SIGMOID = nam::activations::ActivationSigmoid();
 nam::activations::ActivationSwish _SWISH = nam::activations::ActivationSwish();
 nam::activations::ActivationHardSwish _HARD_SWISH = nam::activations::ActivationHardSwish();
@@ -16,7 +17,8 @@ bool nam::activations::Activation::using_fast_tanh = false;
 std::unordered_map<std::string, nam::activations::Activation*> nam::activations::Activation::_activations = {
   {"Tanh", &_TANH},  {"Hardtanh", &_HARD_TANH},   {"Fasttanh", &_FAST_TANH},
   {"ReLU", &_RELU},  {"LeakyReLU", &_LEAKY_RELU}, {"Sigmoid", &_SIGMOID},
-  {"SiLU", &_SWISH}, {"Hardswish", &_HARD_SWISH}, {"LeakyHardtanh", &_LEAKY_HARD_TANH}};
+  {"SiLU", &_SWISH}, {"Hardswish", &_HARD_SWISH}, {"LeakyHardtanh", &_LEAKY_HARD_TANH},
+  {"PReLU", &_PRELU}};
 
 nam::activations::Activation* tanh_bak = nullptr;
 nam::activations::Activation* sigmoid_bak = nullptr;

NAM/activations.h

@@ -202,6 +202,43 @@ class ActivationLeakyReLU : public Activation
   float negative_slope = 0.01;
 };
 
+class ActivationPReLU : public Activation
+{
+public:
+  ActivationPReLU() = default;
+  ActivationPReLU(float ns)
+  {
+    negative_slopes.clear();
+    negative_slopes.push_back(ns);
+  }
+  ActivationPReLU(std::vector<float> ns) { negative_slopes = ns; }
+
+  void apply(Eigen::MatrixXf& matrix) override
+  {
+    // Matrix is organized as (channels, time_steps)
+    int n_channels = negative_slopes.size();
+    int actual_channels = matrix.rows();
+
+    // NOTE: check not done during runtime on release builds
+    // model loader should make sure dimensions match
+    assert(actual_channels == n_channels);
+
+    // Apply each negative slope to its corresponding channel
+    for (int channel = 0; channel < std::min(n_channels, actual_channels); channel++)
+    {
+      // Apply the negative slope to all time steps in this channel
+      for (int time_step = 0; time_step < matrix.rows(); time_step++)
+      {
+        matrix(channel, time_step) = leaky_relu(matrix(channel, time_step), negative_slopes[channel]);
+      }
+    }
+  }
+
+private:
+  std::vector<float> negative_slopes;
+};
+
+
 class ActivationSigmoid : public Activation
 {
 public:

tools/run_tests.cpp

@@ -21,6 +21,11 @@ int main()
   test_activations::TestLeakyReLU::test_get_by_init();
   test_activations::TestLeakyReLU::test_get_by_str();
 
+  test_activations::TestPReLU::test_core_function();
+  test_activations::TestPReLU::test_per_channel_behavior();
+  // This is enforced by an assert so it doesn't need to be tested
+  //test_activations::TestPReLU::test_wrong_number_of_channels();
+
   test_dsp::test_construct();
   test_dsp::test_get_input_level();
   test_dsp::test_get_output_level();

tools/test/test_activations.cpp

@@ -8,6 +8,7 @@
 #include <cassert>
 #include <string>
 #include <vector>
+#include <cmath>
 
 #include "NAM/activations.h"
 
@@ -119,4 +120,79 @@ class TestLeakyReLU
     }
   };
 };
+class TestPReLU
+{
+public:
+  static void test_core_function()
+  {
+    // Test the basic leaky_relu function that PReLU uses
+    auto TestCase = [](float input, float slope, float expectedOutput) {
+      float actualOutput = nam::activations::leaky_relu(input, slope);
+      assert(actualOutput == expectedOutput);
+    };
+
+    // A few snapshot tests
+    TestCase(0.0f, 0.01f, 0.0f);
+    TestCase(1.0f, 0.01f, 1.0f);
+    TestCase(-1.0f, 0.01f, -0.01f);
+    TestCase(-1.0f, 0.05f, -0.05f); // Different slope
+  }
+
+  static void test_per_channel_behavior()
+  {
+    // Test that different slopes are applied to different channels
+    Eigen::MatrixXf data(2, 3); // 2 channels, 3 time steps
+
+    // Initialize with some test data
+    data << -1.0f, 0.5f, 1.0f, -2.0f, -0.5f, 0.0f;
+
+    // Create PReLU with different slopes for each channel
+    std::vector<float> slopes = {0.01f, 0.05f}; // slope 0.01 for channel 0, 0.05 for channel 1
+    nam::activations::ActivationPReLU prelu(slopes);
+
+    // Apply the activation
+    prelu.apply(data);
+
+    // Verify the results
+    // Channel 0 (slope = 0.01):
+    assert(fabs(data(0, 0) - (-0.01f)) < 1e-6); // -1.0 * 0.01 = -0.01
+    assert(fabs(data(0, 1) - 0.5f) < 1e-6); // 0.5 (positive, unchanged)
+    assert(fabs(data(0, 2) - 1.0f) < 1e-6); // 1.0 (positive, unchanged)
+
+    // Channel 1 (slope = 0.05):
+    assert(fabs(data(1, 0) - (-0.10f)) < 1e-6); // -2.0 * 0.05 = -0.10
+    assert(fabs(data(1, 1) - (-0.025f)) < 1e-6); // -0.5 * 0.05 = -0.025
+    assert(fabs(data(1, 2) - 0.0f) < 1e-6); // 0.0 (unchanged)
+  }
+
+  static void test_wrong_number_of_channels()
+  {
+    // Test that we fail when we have more channels than slopes
+    Eigen::MatrixXf data(3, 2); // 3 channels, 2 time steps
+
+    // Initialize with test data
+    data << -1.0f, -1.0f, -1.0f, 1.0f, 1.0f, 1.0f;
+
+    // Create PReLU with only 2 slopes for 3 channels
+    std::vector<float> slopes = {0.01f, 0.05f};
+    nam::activations::ActivationPReLU prelu(slopes);
+
+    // Apply the activation
+    bool caught = false;
+    try
+    {
+      prelu.apply(data);
+    }
+    catch (const std::runtime_error& e)
+    {
+      caught = true;
+    }
+    catch (...)
+    {
+    }
+
+    assert(caught);
+  }
+};
+
 }; // namespace test_activations