From f01a3b2a7f39c03c6532ae7db4b5dc2daba07744 Mon Sep 17 00:00:00 2001
From: Parichay Kapoor <pk.kapoor@samsung.com>
Date: Thu, 9 Dec 2021 20:54:32 +0900
Subject: [PATCH] [lr] Add interface for learning rate scheduler

Add interface for the learning rate scheduler which all learning rate
schedulers must abide by.

Signed-off-by: Parichay Kapoor <pk.kapoor@samsung.com>
---
 nntrainer/optimizers/lr_scheduler.h | 90 +++++++++++++++++++++++++++++++++++++
 1 file changed, 90 insertions(+)
 create mode 100644 nntrainer/optimizers/lr_scheduler.h

diff --git a/nntrainer/optimizers/lr_scheduler.h b/nntrainer/optimizers/lr_scheduler.h
new file mode 100644
index 0000000..6395271
--- /dev/null
+++ b/nntrainer/optimizers/lr_scheduler.h
@@ -0,0 +1,90 @@
+// SPDX-License-Identifier: Apache-2.0
+/**
+ * Copyright (C) 2021 Parichay Kapoor <pk.kapoor@samsung.com>
+ *
+ * @file   lr_scheduler.h
+ * @date   09 December 2021
+ * @brief  This is Learning Rate Scheduler interface class
+ * @see    https://github.com/nnstreamer/nntrainer
+ * @author Parichay Kapoor <pk.kapoor@samsung.com>
+ * @bug    No known bugs except for NYI items
+ *
+ */
+
+#ifndef __LEARNING_RATE_SCHEDULER__
+#define __LEARNING_RATE_SCHEDULER__
+#ifdef __cplusplus
+
+#include <string>
+
+namespace nntrainer {
+
+class Exporter;
+enum class ExportMethods;
+
+/**
+ * @class   Learning Rate Schedulers Base class
+ * @brief   Base class for all Learning Rate Schedulers
+ */
+class LearningRateScheduler {
+
+public:
+  /**
+   * @brief     Destructor of learning rate scheduler Class
+   */
+  virtual ~LearningRateScheduler() = default;
+
+  /**
+   * @brief     get Learning Rate for the given iteration
+   * @param[in] iteration Iteration for the learning rate
+   * @retval    Learning rate in double
+   * @detail    the return value of this function and getInitialLearningRate()
+   * may not match for iteration == 0 (warmup can lead to different initial
+   * learning rates).
+   *
+   * @note this is non-const function intentionally.
+   */
+  virtual double getLearningRate(size_t iteration) = 0;
+
+  /**
+   * @brief this function helps exporting the learning rate in a predefined
+   * format, while workarounding issue caused by templated function type eraser
+   *
+   * @param     exporter exporter that conatins exporting logic
+   * @param     method enum value to identify how it should be exported to
+   */
+  virtual void exportTo(Exporter &exporter, const ExportMethods &method) const {
+  }
+
+  /**
+   * @brief     Default allowed properties
+   * Constant Learning rate scheduler
+   * - learning_rate : float
+   *
+   * Exponential Learning rate scheduler
+   * - learning_rate : float
+   * - decay_rate : float,
+   * - decay_steps : float,
+   *
+   * more to be added
+   */
+
+  /**
+   * @brief     set learning rate scheduler properties
+   * @param[in] values learning rate scheduler properties list
+   * @details   This function accepts vector of properties in the format -
+   *  { std::string property_name = std::string property_val, ...}
+   */
+  virtual void setProperty(const std::vector<std::string> &values) = 0;
+
+  /**
+   * @brief     get learning rate scheduler Type
+   * @retval    learning rate scheduler type
+   */
+  virtual const std::string getType() const = 0;
+};
+
+} /* namespace nntrainer */
+
+#endif /* __cplusplus */
+#endif /* __LEARNING_RATE_SCHEDULER__ */
-- 
2.7.4