From 3eb987279c382e0000de844728aceef2f360acf6 Mon Sep 17 00:00:00 2001
From: Brian Norris <banorris@uci.edu>
Date: Wed, 23 Jan 2013 18:43:14 -0800
Subject: [PATCH] promise: associate Promises with a set of threads

A Promise can be associated with a set of threads, so that we can
perform elimination more efficiently and precisely.
---
 model.cc   |  2 +-
 promise.cc | 55 ++++++++++++++++++++++++++++++++++++++++++------------
 promise.h  | 15 +++++++++++++--
 3 files changed, 57 insertions(+), 15 deletions(-)

diff --git a/model.cc b/model.cc
index c707ff8..9aaab91 100644
--- a/model.cc
+++ b/model.cc
@@ -2475,7 +2475,7 @@ void ModelChecker::mo_check_promises(thread_id_t tid, const ModelAction *write,
 		}
 
 		// Don't do any lookups twice for the same thread
-		if (promise->thread_is_eliminated(tid))
+		if (!promise->thread_is_available(tid))
 			continue;
 
 		if (promise->get_write() && mo_graph->checkReachable(promise->get_write(), write)) {
diff --git a/promise.cc b/promise.cc
index 016b809..e3b8d65 100644
--- a/promise.cc
+++ b/promise.cc
@@ -1,3 +1,6 @@
+#define __STDC_FORMAT_MACROS
+#include <inttypes.h>
+
 #include "promise.h"
 #include "model.h"
 #include "schedule.h"
@@ -13,27 +16,54 @@
 bool Promise::eliminate_thread(thread_id_t tid)
 {
 	unsigned int id = id_to_int(tid);
-	if (id >= eliminated_thread.size())
-		eliminated_thread.resize(id + 1, false);
-	if (eliminated_thread[id])
+	if (!thread_is_available(tid))
 		return false;
 
-	eliminated_thread[id] = true;
+	available_thread[id] = false;
+	num_available_threads--;
 	return has_failed();
 }
 
 /**
- * Check if a thread has already been eliminated from resolving this
- * promise
+ * Add a thread which may resolve this promise
+ *
+ * @param tid The thread ID
+ */
+void Promise::add_thread(thread_id_t tid)
+{
+	unsigned int id = id_to_int(tid);
+	if (id >= available_thread.size())
+		available_thread.resize(id + 1, false);
+	if (!available_thread[id]) {
+		available_thread[id] = true;
+		num_available_threads++;
+	}
+}
+
+/**
+ * Check if a thread is available for resolving this promise. That is, the
+ * thread must have been previously marked for resolving this promise, and it
+ * cannot have been eliminated due to synchronization, etc.
+ *
  * @param tid Thread ID of the thread to check
- * @return True if the thread is already eliminated; false otherwise
+ * @return True if the thread is available; false otherwise
  */
-bool Promise::thread_is_eliminated(thread_id_t tid) const
+bool Promise::thread_is_available(thread_id_t tid) const
 {
 	unsigned int id = id_to_int(tid);
-	if (id >= eliminated_thread.size())
+	if (id >= available_thread.size())
 		return false;
-	return eliminated_thread[id];
+	return available_thread[id];
+}
+
+/** @brief Print debug info about the Promise */
+void Promise::print() const
+{
+	model_print("Promised value %#" PRIx64 ", read from thread %d, available threads to resolve: ", value, read->get_tid());
+	for (unsigned int i = 0; i < available_thread.size(); i++)
+		if (available_thread[i])
+			model_print("[%d]", i);
+	model_print("\n");
 }
 
 /**
@@ -44,10 +74,11 @@ bool Promise::thread_is_eliminated(thread_id_t tid) const
  */
 bool Promise::has_failed() const
 {
-	for (unsigned int i = 1; i < model->get_num_threads(); i++) {
+	for (unsigned int i = 0; i < available_thread.size(); i++) {
 		thread_id_t tid = int_to_id(i);
-		if (!thread_is_eliminated(tid) && model->is_enabled(tid))
+		if (thread_is_available(tid) && model->is_enabled(tid))
 			return false;
 	}
+	ASSERT(num_available_threads == 0);
 	return true;
 }
diff --git a/promise.h b/promise.h
index 3c0d5dd..35515d2 100644
--- a/promise.h
+++ b/promise.h
@@ -22,25 +22,36 @@ struct future_value {
 class Promise {
  public:
 	Promise(ModelAction *act, struct future_value fv) :
+		num_available_threads(0),
 		value(fv.value),
 		expiration(fv.expiration),
 		read(act),
 		write(NULL)
 	{
+		add_thread(fv.tid);
 		eliminate_thread(act->get_tid());
 	}
 	modelclock_t get_expiration() const { return expiration; }
 	ModelAction * get_action() const { return read; }
 	bool eliminate_thread(thread_id_t tid);
-	bool thread_is_eliminated(thread_id_t tid) const;
+	void add_thread(thread_id_t tid);
+	bool thread_is_available(thread_id_t tid) const;
 	bool has_failed() const;
 	uint64_t get_value() const { return value; }
 	void set_write(const ModelAction *act) { write = act; }
 	const ModelAction * get_write() { return write; }
+	int get_num_available_threads() { return num_available_threads; }
+
+	void print() const;
 
 	SNAPSHOTALLOC
  private:
-	std::vector< bool, SnapshotAlloc<bool> > eliminated_thread;
+	/** @brief Thread ID(s) for thread(s) that potentially can satisfy this
+	 *  promise */
+	std::vector< bool, SnapshotAlloc<bool> > available_thread;
+
+	int num_available_threads;
+
 	const uint64_t value;
 	const modelclock_t expiration;
 	ModelAction * const read;
-- 
2.34.1