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Assgn1-FOCC-cs14btech11008.cpp
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Assgn1-FOCC-cs14btech11008.cpp
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#include <iostream>
#include <thread>
#include <fstream>
#include <shared_mutex>
#include <mutex>
#include <time.h>
#include <stdlib.h>
#include <unistd.h>
#include <sstream>
#include <cmath>
#include <vector>
#include <stdio.h>
#include <algorithm>
#include <set>
#include <time.h>
#include <chrono>
#include <random>
/*
SIZE: size of the data items array
lambda: exponential delay parameter
readSet[i]: stores the data-items read by transaction i until now.
writeSet[i]: stores the data-items written by transaction i until now.
liveTrans: stores the ids of transactions are running
*/
const int SIZE = 10;
const int lambda = 3;
int n, m;
std::vector<std::set<int> > readSet;
std::vector<std::set<int> > writeSet;
std::vector<int> liveTrans;
/*
We record the total time taken to complete transactions that are eventually committed
and the number of committed transactions to calculate average transaction time.
NOTE: We don't consider aborted transactions to compute the avg trans time.
*/
long long total_time_taken = 0;
int num_commits = 0;
/*
opNode stores details of a single operation -
op_type can be 'b' - begin, 'd' - delay, 'r' - read, 'w' - write or 'c' - commit
index denotes data item to read or write to.
*/
struct opNode {
char op_type;
int index;
};
/*
The scheduler coordinates access to the common data array by different transactions.
private variables:
data: the data items array (vector)
rw_mutex: mutex lock to execute val-write phase as a critical section.
mtx: mutex lock to add/remove a transaction from liveTrans array.
public methods:
constructor:
- initilise data items array with random elements between 1 to 10.
addToLive (int t):
- add transaction t to the liveTrans array.
removeFromLive (int t, bool success, long time_taken):
- remove transaction t from the liveTrans array.
- if it has been committed then increment num_commits and add transaction time to the total_time_taken.
getData (int tid, int currTrans, int index):
- rw_mtx is locked so that no read from the database is concurrent
with a val-write phase of some other transaction.
valWrite (int currTrans, std::vector<int> &local_data)
- validate against all live transactions t
- if t is not equal currTrans
- if readSet[t] intersection with writeSet[currTrans] is null, validated against t
- else currTrans has to be aborted because of a possible conflict with t, return t
- if validated against all, then copy local data items to the database and return -1
*/
class scheduler {
private:
std::vector<int> data;
std::mutex rw_mtx; std::mutex mtx;
public:
scheduler () {
// initial data items array with a random number between 1 to 10
data.resize (SIZE);
for (int i=0; i<SIZE; i++) {
data[i] = rand() % 10 + 1;
}
printf("Initial data array: ");
for (auto x : data) {
printf("%d ", x);
}
printf("\n");
}
void addToLive (int t) {
mtx.lock ();
liveTrans.push_back (t);
mtx.unlock();
}
void removeFromLive (int t, bool success, long time_taken) {
mtx.lock ();
liveTrans.erase (std::remove(liveTrans.begin(), liveTrans.end(), t), liveTrans.end());
if (success) {
num_commits += 1;
total_time_taken += time_taken;
}
mtx.unlock();
}
void getData (int tid, int currTrans, int index) {
rw_mtx.lock();
readSet[currTrans].insert (index);
printf("Thread %d: Reading data[%d] = %d for transaction #%d\n", tid, index, data[index], currTrans);
rw_mtx.unlock();
}
int valWrite (int currTrans, std::vector<int> &local_data) {
rw_mtx.lock();
std::vector<int> intersect;
for (auto t : liveTrans) {
if (t == currTrans) {
continue;
}
set_intersection (readSet[t].begin(), readSet[t].end(),
writeSet[currTrans].begin(), writeSet[currTrans].end(),
std::back_inserter (intersect));
if (!intersect.empty()) {
rw_mtx.unlock();
return t;
}
}
if (intersect.empty()) {
for (int i=0; i<SIZE; i++) {
if (local_data[i] != -1)
data[i] = local_data[i];
}
rw_mtx.unlock();
return -1;
}
}
};
/*
Method to generate a delay time that is exponentially distributed over parameter lambda.
*/
int delay (int x) {
int sd = std::chrono::system_clock::now().time_since_epoch().count();
std::default_random_engine generator(sd);
std::exponential_distribution <double> distribution(1.0/x);
return (int) distribution(generator);
}
/*
transArr: array of all transactions. Each trans is a vector of opNode
S: instance of scheduler
*/
std::vector<std::vector<opNode> > transArr;
scheduler S;
/*
testTrans method for thread #i
local_data: private version of data items
*/
void testTrans (int i) {
std::vector<int> local_data (SIZE, -1);
int currTrans; int temp;
auto start = std::chrono::steady_clock::now();
auto end = std::chrono::steady_clock::now();
long time_taken;
int failure; bool success;
for (int transIter = 0; transIter < ceil((m * 1.0)/n); transIter++) {
currTrans = transIter * n + i;
if (currTrans > m-1)
continue;
std::fill(local_data.begin(), local_data.end(), -1); // reset local data items
for (auto x : transArr[currTrans]) {
switch (x.op_type) {
case 'b':
start = std::chrono::steady_clock::now();
S.addToLive (currTrans);
printf("Thread %d beginning transaction %d\n", i, currTrans);
break;
case 'r':
S.getData (i, currTrans, x.index);
break;
case 'w':
temp = rand() % 10 + 1;
local_data[x.index] = temp;
printf("Thread %d: Writing data[%d] = %d for transaction #%d\n", i, x.index, local_data[x.index], currTrans);
writeSet[currTrans].insert (x.index);
break;
case 'd':
// sleep (delay(lambda));
usleep((rand() % 10 + 1) * 1000);
break;
case 'c':
failure = S.valWrite (currTrans, local_data);
end = std::chrono::steady_clock::now();
time_taken = std::chrono::duration_cast<std::chrono::milliseconds>(end-start).count();
if (failure == -1) {
printf("Thread %d: Committed transaction #%d successfully\n", i, currTrans);
} else {
printf("Thread %d: Aborted transaction #%d due to conflict with transaction #%d\n", i, currTrans, failure);
}
success = (failure == -1);
S.removeFromLive (currTrans, success, time_taken);
break;
}
}
}
}
int main () {
srand (time(NULL));
freopen ("inp-params.txt", "r", stdin);
freopen("output-focc.txt", "w", stdout);
std::cin >> n >> m; // num_threads num_transactions
transArr.resize(m);
readSet.resize (m, std::set<int> ());
writeSet.resize (m, std::set<int> ());
// read input-params file and populate transArr
std::string temp;
getline (std::cin, temp); // dummy for catching the new line char of line 1
for (int i=0; i<m; i++) {
getline(std::cin, temp);
std::istringstream iss(temp);
std::string op;
while (getline(iss, op, ' ') ) {
opNode a;
if (op[0] == 'r' || op[0] == 'w') {
a.op_type = op[0];
a.index = op[1] - '0';
} else {
a.op_type = op[0];
}
transArr[i].push_back(a);
}
}
std::thread *workers;
workers = new std::thread [n];
for (int i=0; i<n; i++) {
workers[i] = std::thread (testTrans, i);
}
for (int i=0; i<n; i++) {
workers[i].join();
}
printf("Total time taken to commit %d transactions is %lld milliseconds\n", num_commits, total_time_taken);
printf("Average time for a transaction to commit is %f milliseconds\n", total_time_taken / (num_commits * 1.0));
return 0;
}