c++ - openmp bug with radial computation -

#pragma omp parallel schedule(static) default(none) for(int row = 0; row < m_height; row++) {     for(int col = 0; col < m_width; col++)     {        int rysqr, rxsqr;         settingsigman(eta, m_rxinitial + col, m_ryinitial + row , rxsqr, rysqr);         functionusing(rysqr,rxsqr);      } }   void cimagepro::settingsigman(int eta, int x, int y, int &rxsqr, int &rysqr, int &returnvalue) {     int rsqr = getradius(x,y,rxsqr,rysqr);     returnvalue = getnumberfromtable(rsqr); }   int cimagepro::getradius(int x, int y, int &rxsqr, int &rysqr)  {        if (x == m_rxinitial)     {                rxsqr = m_rxsqrinitial;         if (y == m_ryinitial)          {             rysqr = m_rysqrinitial;         }         else if ( abs(y) % 2 == abs(m_ryinitial) % 2)         {             rysqr = rysqr + (y<<2) + 4; //(y+2)^2         }     }      else      {         rxsqr = rxsqr + ( x << 1) + 1; //(x+1)^2     }        return clamp(((rxsqr+rysqr)>>rad_res_reduction),0,(1<<(rad_res-rad_res_reduction))-1); } 

ok here code , problem inside getradius function. since have many threads each threads starts @ different place of x,y. don't understand bug inside getradius().

i thought maybe rysqr computation. can suggest way debug? or can see problem?

update:

this has fixed of code: still don't understand, why there jumps between different threads.

  int cimagepro::getradius(int x, int y, int &rxsqr, int &rysqr)    {       if (x == m_rxinitial)      {               rxsqr = m_rxsqrinitial;      }      else      {          rxsqr = x * x;      }      if (y == m_ryinitial)     {         rysqr = m_rysqrinitial;     }     else if (abs(y) % 2 == abs(m_ryinitial) % 2)     {         rysqr = y * y;     }     return clamp(( (rxsqr + rysqr) >> rad_res_reduction), 0, ( 1 << (rad_res - rad_res_reduction) ) - 1);    } 

i wonder if thing compiles? specify default(none), consistently use data members of class. static?

what either i) leave default(none) away, means default(shared), ii) have shared access values explicitly sharing them, or iii) initialise variables use inside parallel region each thread has it's own private copy of, say, m_rxinitial called p_rxinitial etc. first option guaranteed trouble.

following illustrates option ii):

1) make helper class containing need pass,

struct sharedata{     int s_rxinitial     /* ... */ } 

2) in member function containing parallel section, before parallel loop define

sharedata sd; sd.s_rxinitial = m_rxinitial; /* ... */ 

3) give parallel section

#pragma omp parallel schedule(static), default(none), shared(sd) 

4) use sd datamembers in function calls.

i hope clear enough. appreciate if had more elegant solution offer.

if wanted private variables of option iii), firstprivate(sd) instead of shared(sd). give each thread initialized (to original values) private copy of sd. may or may not give performance advantage avoiding serial access. had similar problem few days ago , there no difference.