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Multi-threaded Solution #8

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Multi-threaded Solution #8

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49 changes: 45 additions & 4 deletions cpp-src/RaceWinnersThreadProblem.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -38,10 +38,22 @@
#include <map>
#include <algorithm>
#include <atomic>
#include <condition_variable>

#undef SCHEDULER
//#define SCHEDULER
using namespace std;

// condition variables to synchronize input and output threads
mutex inMutex;
condition_variable inCondVar;

mutex outMutex;
condition_variable outCondVar;

// pre-conditions for the above condition variables
// setup input thread to run initially
bool inputReady{false}, outputDone{true};

class Runner {
public:
Expand All @@ -58,9 +70,15 @@ class Runner {

void input(list<Runner> &runners) {
#if !defined(SCHEDULER)
cout << "input: ns" << endl;
while (true) {
#endif
// Possible solution Code here

// wait until ouput thread has finished processing the previous
// set of inputs
// note: this will always be true for the first time
unique_lock<mutex> lck(outMutex);
outCondVar.wait(lck,[]{return outputDone;});

vector<unsigned int> ranks(3);
cout <<"Enter ranks for Dave, Jeff, Ben respectively"<<endl;
Expand All @@ -80,7 +98,16 @@ void input(list<Runner> &runners) {
cout << "Invalid Input" << endl;
}

// Possible solution Code here
//set the pre-conditions as appropriate and notify the
//output thread to begin processing
outputDone = false;

{
lock_guard<mutex> lck(inMutex);
inputReady = true;
}
inCondVar.notify_one();

#if !defined(SCHEDULER)
}
#endif
Expand All @@ -92,9 +119,14 @@ bool descending (pair<string, unsigned int> &a, pair<string, unsigned int> &b) {

void output(list<Runner> &runners) {
#if !defined(SCHEDULER)
cout << "output: ns" << endl;
while (true) {
#endif
// Possible solution Code here

// wait until input thread has finished processing
// i.e.: input is available for us to process
unique_lock<mutex> lck(inMutex);
inCondVar.wait(lck,[]{return inputReady;});

vector< pair<string, unsigned int> > winners; // data structure that holds count of Races where Runner Won
for (auto &runner : runners)
Expand All @@ -107,7 +139,16 @@ void output(list<Runner> &runners) {
}
cout<<endl;

// Possible solution Code here
//set the pre-conditions as appropriate and notify the
//input thread to begin processing
inputReady = false;

{
lock_guard<mutex> lck(outMutex);
outputDone = true;
}
outCondVar.notify_one();

#if !defined(SCHEDULER)
}
#endif
Expand Down