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can342man · Apr 27th, 2006, 2:45 PM

Hi everyone,

I am just curious if anyone has come across why a for loop used in a number crunching scheme would hang when and not return the command prompt. No compilation errors and the conditions for the loops are defined.

Just to be more direct, here is the code. It might be too complex but it is fairly simple 10 loops represent summations of a mathematical function and 1 outer loop for indexing them all into an array. This is just the basics of it.

(Toggle Plain Text)

void h1_tm(double *inner1_tm)
{
//h1 variables
	double t1_1a, t1_2a, t1_3a, t1_4a, t1_5a;		//variables
	double re1_1a, im1_1a, re1_2a, im1_2a, tot1_a;		//variables
	double re1_1b, im1_1b, re1_2b, im1_2b, tot1_b;		//conjugates

	int i, j, l, m, n, p;				//indices (int)
//	double j, l, m, n;			//indices (double)

        double c = GSL_CONST_MKSA_SPEED_OF_LIGHT;
        double k = (4.0*M_PI*f_0*R_E*sin(alpha))/c;

        double w_0 = 2.0*M_PI*f_0;             // radial frequency of GW signal
        double w_r = R;           // rotational frequency of Earth
        double w_orb = 1.0;                  // Earth orbital rotational frequency	

//outer loop for indexing total
	for (i = 0; i <= 0; i++) {

//inner summation loops for functions and conjugates
        for (j = 1; j <= 365; j++) {
		for (j = 1; j <= 365; j++) {
			for (p = 0; p <= 5; p++) {
				for (p = 0; p <= 5; p++) {
					for (n = -5; n <= 5; n++) {
					for (n = -5; n <= 5; n++) {
                                for (l = 0; l <= 5; l++) {
			for (l = 0; l <= 5; l++) {
		for (m = l; m <= l; m++) {       
	for (m = l; m <= l; m++) {

//h1 functions
        gsl_complex cpxr1_a = gsl_complex_rect(0.0, 1.0);            // z = 0 + i
        gsl_complex t1_1a = gsl_complex_pow_real(cpxr1_a, l+n);
	im1_1a = GSL_IMAG(t1_1a);
	re1_1a = GSL_REAL(t1_1a); 
        t1_2a = (pow(2.0,0.5)*pow(M_PI,(5.0/2.0)))/w_r;
        t1_3a = (pow(k,l+0.5))/(pow(2.0,2.0*l+1.0));
	t1_5a = gsl_sf_fact(p);
	t1_4a = pow(((-k*k)/16.0),p)/t1_5a;                
        gsl_complex cpxp1_2a = gsl_complex_polar(1.0, M_PI*j*l-M_PI*l);
	re1_2a = GSL_REAL(cpxp1_2a);
	im1_2a = GSL_IMAG(cpxp1_2a);
	tot1_a = im1_1a*re1_1a*t1_2a*t1_3a*t1_4a*im1_2a*re1_2a;
//	cout << tot1_a  << endl;

//h1 conjugates (all other terms same as above except for complex terms)
        gsl_complex cpxr1_b = gsl_complex_rect(0.0, -1.0);            // z = 0 - i
        gsl_complex t1_1b = gsl_complex_pow_real(cpxr1_b, l+n);       
        im1_1b = GSL_IMAG(t1_1b);
        re1_1b = GSL_REAL(t1_1b); 
        gsl_complex cpxp1_2b = gsl_complex_polar(1.0, -1.0*M_PI*j*l-M_PI*l);
        re1_2b = GSL_REAL(cpxp1_2b);
        im1_2b = GSL_IMAG(cpxp1_2b);
        tot1_b = im1_1b*re1_1b*t1_2a*t1_3a*t1_4a*im1_2b*re1_2b;
//      cout << tot1_b  << endl;

	inner1_tm[i] = tot1_b*tot1_a;
//	cout << inner1_tm[i] << endl;

                   					                     }
                                					}
                       						 }
              						  }
      						  }
					}
				}
			}
		}
	}
 }

}

void h1_tm(double *inner1_tm)
{
//h1 variables
	double t1_1a, t1_2a, t1_3a, t1_4a, t1_5a;		//variables
	double re1_1a, im1_1a, re1_2a, im1_2a, tot1_a;		//variables
	double re1_1b, im1_1b, re1_2b, im1_2b, tot1_b;		//conjugates

	int i, j, l, m, n, p;				//indices (int)
//	double j, l, m, n;			//indices (double)

        double c = GSL_CONST_MKSA_SPEED_OF_LIGHT;
        double k = (4.0*M_PI*f_0*R_E*sin(alpha))/c;

        double w_0 = 2.0*M_PI*f_0;             // radial frequency of GW signal
        double w_r = R;           // rotational frequency of Earth
        double w_orb = 1.0;                  // Earth orbital rotational frequency	

//outer loop for indexing total
	for (i = 0; i <= 0; i++) {

//inner summation loops for functions and conjugates
        for (j = 1; j <= 365; j++) {
		for (j = 1; j <= 365; j++) {
			for (p = 0; p <= 5; p++) {
				for (p = 0; p <= 5; p++) {
					for (n = -5; n <= 5; n++) {
					for (n = -5; n <= 5; n++) {
                                for (l = 0; l <= 5; l++) {
			for (l = 0; l <= 5; l++) {
		for (m = l; m <= l; m++) {       
	for (m = l; m <= l; m++) {

//h1 functions
        gsl_complex cpxr1_a = gsl_complex_rect(0.0, 1.0);            // z = 0 + i
        gsl_complex t1_1a = gsl_complex_pow_real(cpxr1_a, l+n);
	im1_1a = GSL_IMAG(t1_1a);
	re1_1a = GSL_REAL(t1_1a); 
        t1_2a = (pow(2.0,0.5)*pow(M_PI,(5.0/2.0)))/w_r;
        t1_3a = (pow(k,l+0.5))/(pow(2.0,2.0*l+1.0));
	t1_5a = gsl_sf_fact(p);
	t1_4a = pow(((-k*k)/16.0),p)/t1_5a;                
        gsl_complex cpxp1_2a = gsl_complex_polar(1.0, M_PI*j*l-M_PI*l);
	re1_2a = GSL_REAL(cpxp1_2a);
	im1_2a = GSL_IMAG(cpxp1_2a);
	tot1_a = im1_1a*re1_1a*t1_2a*t1_3a*t1_4a*im1_2a*re1_2a;
//	cout << tot1_a  << endl;

//h1 conjugates (all other terms same as above except for complex terms)
        gsl_complex cpxr1_b = gsl_complex_rect(0.0, -1.0);            // z = 0 - i
        gsl_complex t1_1b = gsl_complex_pow_real(cpxr1_b, l+n);       
        im1_1b = GSL_IMAG(t1_1b);
        re1_1b = GSL_REAL(t1_1b); 
        gsl_complex cpxp1_2b = gsl_complex_polar(1.0, -1.0*M_PI*j*l-M_PI*l);
        re1_2b = GSL_REAL(cpxp1_2b);
        im1_2b = GSL_IMAG(cpxp1_2b);
        tot1_b = im1_1b*re1_1b*t1_2a*t1_3a*t1_4a*im1_2b*re1_2b;
//      cout << tot1_b  << endl;

	inner1_tm[i] = tot1_b*tot1_a;
//	cout << inner1_tm[i] << endl;

                   					                     }
                                					}
                       						 }
              						  }
      						  }
					}
				}
			}
		}
	}
 }

}

Anyone have any ideas???

Thanks.

:banana:

DaWei · Apr 27th, 2006, 2:55 PM

We're not mind-readers. Post some code. Read about how to post a sensible question somewhere. Eat that freakin' banana, it might help.

stevengs · Apr 27th, 2006, 3:30 PM

I would just start the debugger and step through the loop once.

The Dark · Apr 27th, 2006, 8:11 PM

Whether it is hanging depends on how long you think it should take for 3.5 billion sets of calculations.

DaWei · Apr 27th, 2006, 8:13 PM

ROFL @ Steven and The Dark. See how editing the code in cleared that up?

stevengs · Apr 27th, 2006, 11:55 PM

hmmm ..I wonder if he is still stepping

..how to keep a canman occupied

andro · Apr 28th, 2006, 12:29 AM

What I want to know is what he THOUGHT that code was going to do...

can342man · Apr 28th, 2006, 9:01 AM

The code is just one part of a long calculation for the gravitational wave signal from a pulsar star. The mathematical functions are not that significant in this particular problem. It is mainly a for loop problem and hence the whole thing can be reduced to a simple for loop question.

I will try the debugger.

Thanks

grumpy · Apr 28th, 2006, 9:57 AM

Given that some of your inner loops are changing variables that control your outer loops, it is a little hard to predict the behaviour of your program at first glance.

I'm not necessarily sure that the loops are infinite, but you will certainly find the sequence entertaining when stepping through in a debugger.

andro · Apr 28th, 2006, 2:43 PM

1*365*365*6*6*11*11*6*6*1*1=20891811600

That's 20,891,811,600 times you are calculating whatever is inside the for loops. I think there is a mistake in your logic somewhere..?

Apr 27th, 2006, 2:45 PM	#1
can342man Newbie Join Date: Jan 2006 Location: London, Ontario, Canada Posts: 16 Rep Power: 0	Hanging For loop in C++ Hi everyone, I am just curious if anyone has come across why a for loop used in a number crunching scheme would hang when and not return the command prompt. No compilation errors and the conditions for the loops are defined. Just to be more direct, here is the code. It might be too complex but it is fairly simple 10 loops represent summations of a mathematical function and 1 outer loop for indexing them all into an array. This is just the basics of it. (Toggle Plain Text) void h1_tm(double inner1_tm) { //h1 variables double t1_1a, t1_2a, t1_3a, t1_4a, t1_5a; //variables double re1_1a, im1_1a, re1_2a, im1_2a, tot1_a; //variables double re1_1b, im1_1b, re1_2b, im1_2b, tot1_b; //conjugates int i, j, l, m, n, p; //indices (int) // double j, l, m, n; //indices (double) double c = GSL_CONST_MKSA_SPEED_OF_LIGHT; double k = (4.0M_PIf_0R_Esin(alpha))/c; double w_0 = 2.0M_PIf_0; // radial frequency of GW signal double w_r = R; // rotational frequency of Earth double w_orb = 1.0; // Earth orbital rotational frequency //outer loop for indexing total for (i = 0; i <= 0; i++) { //inner summation loops for functions and conjugates for (j = 1; j <= 365; j++) { for (j = 1; j <= 365; j++) { for (p = 0; p <= 5; p++) { for (p = 0; p <= 5; p++) { for (n = -5; n <= 5; n++) { for (n = -5; n <= 5; n++) { for (l = 0; l <= 5; l++) { for (l = 0; l <= 5; l++) { for (m = l; m <= l; m++) { for (m = l; m <= l; m++) { //h1 functions gsl_complex cpxr1_a = gsl_complex_rect(0.0, 1.0); // z = 0 + i gsl_complex t1_1a = gsl_complex_pow_real(cpxr1_a, l+n); im1_1a = GSL_IMAG(t1_1a); re1_1a = GSL_REAL(t1_1a); t1_2a = (pow(2.0,0.5)pow(M_PI,(5.0/2.0)))/w_r; t1_3a = (pow(k,l+0.5))/(pow(2.0,2.0l+1.0)); t1_5a = gsl_sf_fact(p); t1_4a = pow(((-kk)/16.0),p)/t1_5a; gsl_complex cpxp1_2a = gsl_complex_polar(1.0, M_PIjl-M_PIl); re1_2a = GSL_REAL(cpxp1_2a); im1_2a = GSL_IMAG(cpxp1_2a); tot1_a = im1_1are1_1at1_2at1_3at1_4aim1_2are1_2a; // cout << tot1_a << endl; //h1 conjugates (all other terms same as above except for complex terms) gsl_complex cpxr1_b = gsl_complex_rect(0.0, -1.0); // z = 0 - i gsl_complex t1_1b = gsl_complex_pow_real(cpxr1_b, l+n); im1_1b = GSL_IMAG(t1_1b); re1_1b = GSL_REAL(t1_1b); gsl_complex cpxp1_2b = gsl_complex_polar(1.0, -1.0M_PIjl-M_PIl); re1_2b = GSL_REAL(cpxp1_2b); im1_2b = GSL_IMAG(cpxp1_2b); tot1_b = im1_1bre1_1bt1_2at1_3at1_4aim1_2bre1_2b; // cout << tot1_b << endl; inner1_tm[i] = tot1_btot1_a; // cout << inner1_tm[i] << endl; } } } } } } } } } } } } void h1_tm(double inner1_tm) { //h1 variables double t1_1a, t1_2a, t1_3a, t1_4a, t1_5a; //variables double re1_1a, im1_1a, re1_2a, im1_2a, tot1_a; //variables double re1_1b, im1_1b, re1_2b, im1_2b, tot1_b; //conjugates int i, j, l, m, n, p; //indices (int) // double j, l, m, n; //indices (double) double c = GSL_CONST_MKSA_SPEED_OF_LIGHT; double k = (4.0M_PIf_0R_Esin(alpha))/c; double w_0 = 2.0M_PIf_0; // radial frequency of GW signal double w_r = R; // rotational frequency of Earth double w_orb = 1.0; // Earth orbital rotational frequency //outer loop for indexing total for (i = 0; i <= 0; i++) { //inner summation loops for functions and conjugates for (j = 1; j <= 365; j++) { for (j = 1; j <= 365; j++) { for (p = 0; p <= 5; p++) { for (p = 0; p <= 5; p++) { for (n = -5; n <= 5; n++) { for (n = -5; n <= 5; n++) { for (l = 0; l <= 5; l++) { for (l = 0; l <= 5; l++) { for (m = l; m <= l; m++) { for (m = l; m <= l; m++) { //h1 functions gsl_complex cpxr1_a = gsl_complex_rect(0.0, 1.0); // z = 0 + i gsl_complex t1_1a = gsl_complex_pow_real(cpxr1_a, l+n); im1_1a = GSL_IMAG(t1_1a); re1_1a = GSL_REAL(t1_1a); t1_2a = (pow(2.0,0.5)pow(M_PI,(5.0/2.0)))/w_r; t1_3a = (pow(k,l+0.5))/(pow(2.0,2.0l+1.0)); t1_5a = gsl_sf_fact(p); t1_4a = pow(((-kk)/16.0),p)/t1_5a; gsl_complex cpxp1_2a = gsl_complex_polar(1.0, M_PIjl-M_PIl); re1_2a = GSL_REAL(cpxp1_2a); im1_2a = GSL_IMAG(cpxp1_2a); tot1_a = im1_1are1_1at1_2at1_3at1_4aim1_2are1_2a; // cout << tot1_a << endl; //h1 conjugates (all other terms same as above except for complex terms) gsl_complex cpxr1_b = gsl_complex_rect(0.0, -1.0); // z = 0 - i gsl_complex t1_1b = gsl_complex_pow_real(cpxr1_b, l+n); im1_1b = GSL_IMAG(t1_1b); re1_1b = GSL_REAL(t1_1b); gsl_complex cpxp1_2b = gsl_complex_polar(1.0, -1.0M_PIjl-M_PIl); re1_2b = GSL_REAL(cpxp1_2b); im1_2b = GSL_IMAG(cpxp1_2b); tot1_b = im1_1bre1_1bt1_2at1_3at1_4aim1_2bre1_2b; // cout << tot1_b << endl; inner1_tm[i] = tot1_btot1_a; // cout << inner1_tm[i] << endl; } } } } } } } } } } } } Anyone have any ideas??? Thanks. :banana: __________________ Greatness courts failure and solitude. --- Anonymous Last edited by can342man; Apr 27th, 2006 at 3:03 PM.

Apr 27th, 2006, 2:55 PM	#2
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	We're not mind-readers. Post some code. Read about how to post a sensible question somewhere. Eat that freakin' banana, it might help. __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

Apr 27th, 2006, 3:30 PM	#3
stevengs Professional Programmer Join Date: May 2005 Location: Bad Nauheim, Germany Posts: 436 Rep Power: 4	I would just start the debugger and step through the loop once. __________________ -Steven "Is this a piece of your brain?" - Basil Fawlty

Apr 27th, 2006, 8:13 PM	#5
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	ROFL @ Steven and The Dark. See how editing the code in cleared that up? __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

Apr 27th, 2006, 11:55 PM	#6
stevengs Professional Programmer Join Date: May 2005 Location: Bad Nauheim, Germany Posts: 436 Rep Power: 4	hmmm ..I wonder if he is still stepping ..how to keep a canman occupied __________________ -Steven "Is this a piece of your brain?" - Basil Fawlty

Apr 27th, 2006, 8:11 PM	#4
The Dark Expert Programmer Join Date: Jun 2005 Posts: 850 Rep Power: 4	Whether it is hanging depends on how long you think it should take for 3.5 billion sets of calculations.

Apr 28th, 2006, 12:29 AM	#7
andro Professional Programmer Join Date: Oct 2005 Location: California Posts: 309 Rep Power: 3	What I want to know is what he THOUGHT that code was going to do...

Apr 28th, 2006, 9:01 AM	#8
can342man Newbie Join Date: Jan 2006 Location: London, Ontario, Canada Posts: 16 Rep Power: 0	The code is just one part of a long calculation for the gravitational wave signal from a pulsar star. The mathematical functions are not that significant in this particular problem. It is mainly a for loop problem and hence the whole thing can be reduced to a simple for loop question. I will try the debugger. Thanks __________________ Greatness courts failure and solitude. --- Anonymous

Apr 28th, 2006, 9:57 AM	#9
grumpy Programming Guru Join Date: Jun 2005 Location: Adelaide, South Australia Posts: 1,221 Rep Power: 5	Given that some of your inner loops are changing variables that control your outer loops, it is a little hard to predict the behaviour of your program at first glance. I'm not necessarily sure that the loops are infinite, but you will certainly find the sequence entertaining when stepping through in a debugger.

Apr 28th, 2006, 2:43 PM	#10
andro Professional Programmer Join Date: Oct 2005 Location: California Posts: 309 Rep Power: 3	13653656611116611=20891811600 That's 20,891,811,600 times you are calculating whatever is inside the for loops. I think there is a mistake in your logic somewhere..?

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Hanging For loop in C++