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POC: performance of pthread, low than single thrad
 

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  1. POC: performance of pthread, low than single thrad
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    <p>I'm confusing about the performance of my code, when dealing with single thread it only using 13s, but it's will consume 80s. I don't know whether the vector can only be accessed by one thread at a time, if so it's likely I have to use a struct array to store data instead of vector, could anyone kindly help?</p> <pre><code>#include &lt;iostream&gt; #include &lt;stdio.h&gt; #include &lt;stdlib.h&gt; #include &lt;vector&gt; #include &lt;iterator&gt; #include &lt;string&gt; #include &lt;ctime&gt; #include &lt;bangdb/database.h&gt; #include "SEQ.h" #define NUM_THREADS 16 using namespace std; typedef struct _thread_data_t { std::vector&lt;FDT&gt; *Query; unsigned long start; unsigned long end; connection* conn; int thread; } thread_data_t; void *thr_func(void *arg) { thread_data_t *data = (thread_data_t *)arg; std::vector&lt;FDT&gt; *Query = data-&gt;Query; unsigned long start = data-&gt;start; unsigned long end = data-&gt;end; connection* conn = data-&gt;conn; printf("thread %d started %lu -&gt; %lu\n", data-&gt;thread, start, end); for (unsigned long i=start;i&lt;=end ;i++ ) { FDT *fout = conn-&gt;get(&amp;((*Query).at(i))); if (fout == NULL) { //printf("%s\tNULL\n", s); } else { printf("Thread:%d\t%s\n", data-&gt;thread, fout-&gt;data); } } pthread_exit(NULL); } int main(int argc, char *argv[]) { if (argc&lt;2) { printf("USAGE: ./seq &lt;.txt&gt;\n"); printf("/home/rd/SCRIPTs/12X18610_L5_I052.R1.clean.code.seq\n"); exit(-1); } printf("%s\n", argv[1]); vector&lt;FDT&gt; Query; FILE* fpin; if((fpin=fopen(argv[1],"r"))==NULL) { printf("Can't open Input file %s\n", argv[1]); return -1; } char *key = (char *)malloc(36); while (fscanf(fpin, "%s", key) != EOF) { SEQ * sequence = new SEQ(key); FDT *fk = new FDT( (void*)sequence, sizeof(*sequence) ); Query.push_back(*fk); } unsigned long Querysize = (unsigned long)(Query.size()); std::cout &lt;&lt; "myvector stores " &lt;&lt; Querysize &lt;&lt; " numbers.\n"; //create database, table and connection database* db = new database((char*)"berrydb"); //get a table, a new one or existing one, walog tells if log is on or off table* tbl = db-&gt;gettable((char*)"hg19", JUSTOPEN); if(tbl == NULL) { printf("ERROR:table NULL error"); exit(-1); } //get a new connection connection* conn = tbl-&gt;getconnection(); if(conn == NULL) { printf("ERROR:connection NULL error"); exit(-1); } cerr&lt;&lt;"begin querying...\n"; time_t begin, end; double duration; begin = clock(); unsigned long ThreadDealSize = Querysize/NUM_THREADS; cerr&lt;&lt;"Querysize:"&lt;&lt;ThreadDealSize&lt;&lt;endl; pthread_t thr[NUM_THREADS]; int rc; thread_data_t thr_data[NUM_THREADS]; for (int i=0;i&lt;NUM_THREADS ;i++ ) { unsigned long ThreadDealStart = ThreadDealSize*i; unsigned long ThreadDealEnd = ThreadDealSize*(i+1) - 1; if (i == (NUM_THREADS-1) ) { ThreadDealEnd = Querysize-1; } thr_data[i].conn = conn; thr_data[i].Query = &amp;Query; thr_data[i].start = ThreadDealStart; thr_data[i].end = ThreadDealEnd; thr_data[i].thread = i; } for (int i=0;i&lt;NUM_THREADS ;i++ ) { if (rc = pthread_create(&amp;thr[i], NULL, thr_func, &amp;thr_data[i])) { fprintf(stderr, "error: pthread_create, rc: %d\n", rc); return EXIT_FAILURE; } } for (int i = 0; i &lt; NUM_THREADS; ++i) { pthread_join(thr[i], NULL); } cerr&lt;&lt;"done\n"&lt;&lt;endl; end = clock(); duration = double(end - begin) / CLOCKS_PER_SEC; cerr &lt;&lt; "runtime: " &lt;&lt; duration &lt;&lt; "\n" &lt;&lt; endl; db-&gt;closedatabase(OPTIMISTIC); delete db; printf("Done\n"); return EXIT_SUCCESS; } </code></pre>
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    1. USimreal
    1. USuser1744416
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      1. POC: performance of pthread, low than single thrad
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    1. COIt may happen some time single threaded code is faster then multi-threaded because of context-switching time in threading program
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      1. POC: performance of pthread, low than single thrad
      1. USGrijesh Chauhan
 

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