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Illegal 4 instruction on Mac using C ++

I run this code on my mac (10.8.2) through the terminal, and for some n it ends with "Illegal instruction 4", does anyone know why or how to stop it?

I am confused as the code works fine except n = 43, 45, 47 and 57.

Also after n = 60 this happens for all n. This may be a memory issue, as it works fine at lower n values.

Note: everything related to the integer c comes down to decreasing the first while loop. It is preferable that the while loop read b <251 to give me 250 iterations, but instead I run something like b <51 for c = 1,2,3,4,5 to get 5 different files with 50 results, not 1 with 250.

The code is as follows:

#include <stdio.h> #include <string.h> #include <math.h> #include <iostream> #include <iomanip> #include <fstream> #include <time.h> #include <stdlib.h> #include <sstream> using namespace std; int main() { int a,b,c,f,i,j,k,m,n,s; double p,Time,Averagetime,Energy,energy,Distance,Length,DotProdForce,Forcemagnitude, ForceMagnitude[101],Force[101][4],E[10001],En[501],x[101][4],y[101][4]; clock_t t1,t2; t1=clock(); b=1; c=1; Time=0.0; while(b<251){ clock_t t3,t4; t3=clock(); /* set the number of points */ n=45; /* check that there are no more than 100 points */ if(n>100){ cout << n << " is too many points for me :-( \n"; exit(0); } /* reset the random number generator */ srand((unsigned)time(0)); for (i=1;i<=n;i++){ x[i][1]=((rand()*1.0)/(1.0*RAND_MAX)-0.5)*2.0; x[i][2]=((rand()*1.0)/(1.0*RAND_MAX)-0.5)*2.0; x[i][3]=((rand()*1.0)/(1.0*RAND_MAX)-0.5)*2.0; Length=sqrt(pow(x[i][1],2)+pow(x[i][2],2)+pow(x[i][3],2)); for (k=1;k<=3;k++){ x[i][k]=x[i][k]/Length; } } /* calculate the energy */ Energy=0.0; for(i=1;i<=n;i++){ for(j=i+1;j<=n;j++){ Distance=sqrt(pow(x[i][1]-x[j][1],2)+pow(x[i][2]-x[j][2],2) +pow(x[i][3]-x[j][3],2)); Energy=Energy+1.0/Distance; } } /* Save Original Points */ for(i=1;i<=n;i++){ y[i][1]=x[i][1]; y[i][2]=x[i][2]; y[i][3]=x[i][3]; } /* Loop for random points m times*/ m=10; if (m>100){ cout << "The m="<< m << " loop is inefficient...lessen m \n"; exit(0); } a=1; while(a<m){ /* assign random points */ for (i=1;i<=n;i++){ x[i][1]=((rand()*1.0)/(1.0*RAND_MAX)-0.5)*2.0; x[i][2]=((rand()*1.0)/(1.0*RAND_MAX)-0.5)*2.0; x[i][3]=((rand()*1.0)/(1.0*RAND_MAX)-0.5)*2.0; Length=sqrt(pow(x[i][1],2)+pow(x[i][2],2)+pow(x[i][3],2)); for (k=1;k<=3;k++){ x[i][k]=x[i][k]/Length; } } /* calculate the energy */ energy=0.0; for(i=1;i<=n;i++){ for(j=i+1;j<=n;j++){ Distance=sqrt(pow(x[i][1]-x[j][1],2)+pow(x[i][2]-x[j][2],2) +pow(x[i][3]-x[j][3],2)); energy=energy+1.0/Distance; } } if(energy<Energy) for(i=1;i<=n;i++){ for(j=1;j<=3;j++){ Energy=energy; y[i][j]=x[i][j]; } } else for(i=1;i<=n;i++){ for(j=1;j<=3;j++){ energy=Energy; x[i][j]=y[i][j]; } } a=a+1; } /* Create string stream 1 */ ostringstream String1; String1 << "Bestrandonpoints_" << n; //add number /* Output these points */ ofstream File1 (String1.str().c_str()); File1 << "Energy=" << Energy << "\n"; for(i=1;i<=n;i++){ File1 << x[i][1] << " " << x[i][2] << " " << x[i][3] << "\n"; } File1.close(); /* For energy file later */ E[0]=Energy; /* Start doing gradient flow approach */ a=1; s=0; f=0; Forcemagnitude=1.0; if(n>80) p=0.005; else if(n>60) p=0.01; else if(n>40) p=0.02; else p=0.05; while(Forcemagnitude>0.00005){ /* Reset initial force and energy change */ for(i=1;i<=n;i++){ Force[i][1]=0.0; Force[i][2]=0.0; Force[i][3]=0.0; } /* Calculate force on each particle */ for(i=1;i<=n;i++){ for(j=1;j<i;j++){ Distance=sqrt(pow(x[i][1]-x[j][1],2)+pow(x[i][2]-x[j][2],2) +pow(x[i][3]-x[j][3],2)); Force[i][1]=Force[i][1]+((x[i][1]-x[j][1])/(pow((Distance),3))); Force[i][2]=Force[i][2]+((x[i][2]-x[j][2])/(pow((Distance),3))); Force[i][3]=Force[i][3]+((x[i][3]-x[j][3])/(pow((Distance),3))); } for (j=i+1;j<=n;j++){ Distance=sqrt(pow(x[i][1]-x[j][1],2)+pow(x[i][2]-x[j][2],2) +pow(x[i][3]-x[j][3],2)); Force[i][1]=Force[i][1]+((x[i][1]-x[j][1])/(pow((Distance),3))); Force[i][2]=Force[i][2]+((x[i][2]-x[j][2])/(pow((Distance),3))); Force[i][3]=Force[i][3]+((x[i][3]-x[j][3])/(pow((Distance),3))); } } /* Add the force to my points */ for(i=1;i<=n;i++){ DotProdForce=Force[i][1]*x[i][1]+Force[i][2]*x[i][2]+Force[i][3]*x[i][3]; y[i][1]=x[i][1]; y[i][2]=x[i][2]; y[i][3]=x[i][3]; Force[i][1]=Force[i][1]-DotProdForce*y[i][1]; Force[i][2]=Force[i][2]-DotProdForce*y[i][2]; Force[i][3]=Force[i][3]-DotProdForce*y[i][3]; x[i][1] = y[i][1]+p*(Force[i][1]); x[i][2] = y[i][2]+p*(Force[i][2]); x[i][3] = y[i][3]+p*(Force[i][3]); /* Bring it back onto sphere */ Length=sqrt(pow(x[i][1],2)+pow(x[i][2],2)+pow(x[i][3],2)); for (j=1;j<=3;j++){ x[i][j]=x[i][j]/Length; } } /* Calculate the new energy */ energy=0.0; for(i=1;i<=n;i++){ for(j=i+1;j<=n;j++){ Distance=sqrt(pow(x[i][1]-x[j][1],2)+pow(x[i][2]-x[j][2],2) +pow(x[i][3]-x[j][3],2)); energy=energy+1.0/Distance; } } E[a]=energy; /* Choose best energy and therefore best points */ if (energy<Energy) Energy=energy,s=s+1; else energy=Energy,f=f+1,p=(9.5*p)/10; for(i=1;i<=n;i++){ ForceMagnitude[i]=pow((pow(Force[i][1],2)+pow(Force[i][2],2) +pow(Force[i][3],2)),0.5); } for(i=1;i<=n-1;i++){ if(ForceMagnitude[i]<ForceMagnitude[i+1]) ForceMagnitude[i]=ForceMagnitude[i+1]; else ForceMagnitude[i+1]=ForceMagnitude[i]; } Forcemagnitude=ForceMagnitude[n]; a=a+1; } En[b]=Energy; b=b+1; t4=clock(); float diff ((float)t4-(float)t3); float seconds = diff / CLOCKS_PER_SEC; Time = Time + seconds; } Averagetime = Time/(b-1); cout << fixed << setprecision (4) << "Average Time: " << Averagetime << "(s) \n"; cout << fixed << setprecision(10) << "Energy=" << Energy << "\n"; t2=clock(); float diff ((float)t2-(float)t1); float seconds = diff / CLOCKS_PER_SEC; /* Create string stream 2 */ ostringstream String2; String2 << "GFPoints_" << n; //add number /* Output these points */ ofstream File2 (String2.str().c_str()); for(i=1;i<=n;i++){ File2 << x[i][1] << " " << x[i][2] << " " << x[i][3] << "\n"; } File2.close(); /* Create string stream 3 */ ostringstream String3; String3 << "GFEnergies_" << n; //add number /* Output these points */ ofstream File3 (String3.str().c_str()); for(i=1;i<a;i++){ File3 << fixed << setprecision (10) << E[i] << "\n"; } File3.close(); /* Output to help with gnuin.txt */ ofstream File4 ("mypoints"); for(i=1;i<=n;i++){ File4 << x[i][1] << " " << x[i][2] << " " << x[i][3] << "\n"; } File4.close(); /* Create string stream 4 */ ostringstream String4; String4 << "GFInfo_" << n; //add number /* Output these points */ ofstream File5 (String4.str().c_str()); File5 << "Iterations=" << a-1 << "\n"; File5 << "Successes=" << s << " Failures=" << f << "\n"; File5 << fixed << setprecision(20) << "Energy=" << Energy << "\n"; File5 << fixed << setprecision(5) << "Total run time: " << seconds << "(s) \n"; File5 << fixed << setprecision(5) << "Average run time: " << Averagetime << "(s) \n"; File5.close(); /* Create string stream 5 */ ostringstream String5; String5 << "GF%Energies_" << n << "_" << c; //add number /* Output these points */ ofstream File6 (String5.str().c_str()); for(i=1;i<b;i++){ File6 << fixed << setprecision(20) << En[i] << "\n"; } File6.close(); cout << fixed << setprecision(5) << "Run time: " << seconds << "(s)" << "\n"; return 0; }

Thanks for any light you spread on the subject, A.

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2 answers

The obvious issues are the following lines:

 E[a]=energy; En[b]=Energy;

You increase a and b at each iteration of the loop, but do not check them at the boundaries of a fixed array; therefore, if loops are repeated too many times, you will write outside arrays.

You might want to replace them with dynamic arrays ( std::vector<double> ) or perhaps you want to abort if a or b gets too large.

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Try compiling with:

 -mmacosx-version-min=10.6
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Source: https://habr.com/ru/post/1236144/

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