From 3afacb7702e6d8fa67749a2a41dc776d315e02a9 Mon Sep 17 00:00:00 2001
From: Douglas Rumbaugh <dbr4@psu.edu>
Date: Mon, 23 Oct 2023 17:43:22 -0400
Subject: Began moving to an explicit epoch-based system

I started moving over to an explicit Epoch based system, which has
necessitated a ton of changes throughout the code base. This will
ultimately allow for a much cleaner set of abstractions for managing
concurrency.
---
 include/framework/scheduling/FIFOScheduler.h | 96 ++++++++++++++++++++++++++++
 1 file changed, 96 insertions(+)
 create mode 100644 include/framework/scheduling/FIFOScheduler.h

(limited to 'include/framework/scheduling/FIFOScheduler.h')

diff --git a/include/framework/scheduling/FIFOScheduler.h b/include/framework/scheduling/FIFOScheduler.h
new file mode 100644
index 0000000..878bb81
--- /dev/null
+++ b/include/framework/scheduling/FIFOScheduler.h
@@ -0,0 +1,96 @@
+/*
+ * include/framework/Scheduler.h
+ *
+ * Copyright (C) 2023 Douglas B. Rumbaugh <drumbaugh@psu.edu> 
+ *                    Dong Xie <dongx@psu.edu>
+ *
+ * All rights reserved. Published under the Modified BSD License.
+ *
+ */
+#pragma once
+
+#include <vector>
+#include <memory>
+#include <queue>
+#include <thread>
+#include <condition_variable>
+#include <future>
+
+#include "util/types.h"
+#include "framework/interface/Shard.h"
+#include "framework/interface/Query.h"
+#include "framework/interface/Record.h"
+#include "framework/structure/MutableBuffer.h"
+#include "framework/util/Configuration.h"
+#include "framework/structure/ExtensionStructure.h"
+#include "framework/scheduling/Task.h"
+
+#include "psu-ds/LockedPriorityQueue.h"
+
+namespace de {
+
+class FIFOScheduler {
+public:
+    FIFOScheduler(size_t memory_budget, size_t thread_cnt)
+      : m_memory_budget((memory_budget) ? memory_budget : UINT64_MAX)
+      , m_thrd_cnt((thread_cnt) ? thread_cnt: UINT64_MAX)
+      , m_used_memory(0)
+      , m_used_thrds(0)
+      , m_shutdown(false)
+    {
+        m_sched_thrd = std::thread(&FIFOScheduler::run, this);
+    }
+
+    ~FIFOScheduler() {
+        shutdown();
+
+        m_cv.notify_all();
+        m_sched_thrd.join();
+    }
+
+    void schedule_job(std::function<void(void*)> job, size_t size, void *args) {
+        size_t ts = m_counter.fetch_add(1);
+        m_task_queue.push(Task(size, ts, job, args));
+        m_cv.notify_all();
+    }
+
+    void shutdown() {
+        m_shutdown = true;
+    }
+
+private:
+    psudb::LockedPriorityQueue<Task> m_task_queue;
+
+    size_t m_memory_budget;
+    size_t m_thrd_cnt;
+
+    bool m_shutdown; 
+
+    std::atomic<size_t> m_counter;
+    std::mutex m_cv_lock;
+    std::condition_variable m_cv;
+
+    std::thread m_sched_thrd;
+
+    std::atomic<size_t> m_used_thrds;
+    std::atomic<size_t> m_used_memory;
+
+    void schedule_next() {
+        auto t = m_task_queue.pop();
+        t();
+    }
+
+    void run() {
+        do {
+            std::unique_lock<std::mutex> cv_lock(m_cv_lock);
+            m_cv.wait(cv_lock);
+
+            while (m_task_queue.size() > 0 && m_used_thrds.load() < m_thrd_cnt) {
+                schedule_next();
+            }
+            cv_lock.unlock();
+        } while(!m_shutdown);
+    }
+};
+
+}
-- 
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