#include <math.h>

[Darius Fatakia]

Hi,

I seem to be having trouble with some of my math functions (pow, sqrt,
acos). They're the only ones I use in my code and they prevent the program
from compiling. I get a "undefined reference to 'pow'" error. Here is the
relevant portion of my code.

Your help would be appreciated. Thanks!

* Genetic Algorithm module
*
*/

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <math.h>
#include "string.h"
/* GetSD
*
* This function returns the standard deviation of the feature vectors
* in a dataT * array.
*/
static double GetSD(dataT *dataArr[], int data_size, int features[], double
mean[]) {
int i, j;
double data_vect[GENES_PER_CHROM], data_sum, mean_sum, ang_sum, dotprod,
data_norm, mean_norm, angle;
double sd;

ang_sum = 0;

for(i = 0; i < data_size; i++) {
for(j = 0; j < GENES_PER_CHROM ; j++) {
data_vect[j] = dataArr[i]->val[(features[j])];
}

// get dot product of the two vectors
dotprod = 0;
for(j = 0; j < GENES_PER_CHROM ; j++) {
dotprod += data_vect[j] * mean[j];
}

// get the norms
data_sum = 0;
mean_sum = 0;
for(j = 0; j < GENES_PER_CHROM ; j++) {
data_sum += pow(data_vect[j], 2);
mean_sum += pow(mean[j], 2);
}
data_norm = sqrt(data_sum);
mean_norm = sqrt(mean_sum);

// compute the angle
angle = acos(dotprod/(data_norm * mean_norm));

ang_sum += pow(angle, 2);
}

sd = sqrt(ang_sum / (data_size - 1));

return sd;
}

[Alex]

Darius Fatakia <da************ @yahoo.com> wrote:

Hi, I seem to be having trouble with some of my math functions (pow, sqrt,
acos). They're the only ones I use in my code and they prevent the program
from compiling. I get a "undefined reference to 'pow'" error. Here is the
relevant portion of my code.

You are most likely having a linking problem. Read your system
documentation to find out how to link in the math library.

<OT> Appending -lm to your compile line might work. </OT>

Alex

[E. Robert Tisdale]

Darius Fatakia wrote:

I seem to be having trouble with some of my math functions (pow, sqrt,
acos). They're the only ones I use in my code and they prevent the program
from compiling. I get a "undefined reference to 'pow'" error. Here is the
relevant portion of my code. cat gam.c typedef struct dataT {
double* val;
} dataT;

#define GENES_PER_CHROM 1024

/*
* Genetic Algorithm module
*/

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <math.h>
#include "string.h"
/* GetSD
*
* This function returns the standard deviation
* of the feature vectors in a dataT* array.
*/

static
double GetSD(dataT* dataArr[],
int data_size, int features[], double mean[]) {
double data_vect[GENES_PER_CHROM];
double ang_sum = 0.0;

for(int i = 0; i < data_size; ++i) {
for(int j = 0; j < GENES_PER_CHROM ; ++j) {
data_vect[j] = dataArr[i]->val[(features[j])];
}

// get dot product of the two vectors
double dotprod = 0.0;
for(int j = 0; j < GENES_PER_CHROM ; ++j) {
dotprod += data_vect[j]*mean[j];
}

// get the norms
double data_sum = 0.0;
double mean_sum = 0.0;
for(int j = 0; j < GENES_PER_CHROM ; ++j) {
data_sum += pow(data_vect[j], 2);
mean_sum += pow(mean[j], 2);
}
double data_norm = sqrt(data_sum);
double mean_norm = sqrt(mean_sum);

// compute the angle
double angle = acos(dotprod/(data_norm*mean _norm));
ang_sum += pow(angle, 2);
}
return sqrt(ang_sum/(data_size - 1));
}

int main(int argc, char* argv[]) {
dataT* dataArr[GENES_PER_CHROM];
int data_size = 1024;
int features[1024];
double mean[GENES_PER_CHROM];
GetSD(dataArr, data_size, features, mean);

return 0;
}
gcc -Wall -std=c99 -pedantic -o gam gam.c -lm

If you include math.h, you need to link in libm.a with the -lm option.

[Kelsey Bjarnason]

On Mon, 24 Nov 2003 16:52:07 -0800, Darius Fatakia wrote:

Hi,

I seem to be having trouble with some of my math functions (pow, sqrt,
acos). They're the only ones I use in my code and they prevent the program
from compiling. I get a "undefined reference to 'pow'" error. Here is the
relevant portion of my code.

Sounds like a linker error - are you linking the math libraries? There's
a certain, popular compiler, especially widely used in the Linux world,
which has the terminally brain-dead habit of not including the math
libraries by default. Assuming you're using this compiler, try something
like this:

gcc -lm file.c

[jacob navia]

I wonder how many HUNDREDS of times I have seen this question
pop up.

Are there any gcc fans out here?

Wouldn't it be time to include that library as a default library????

eh? !!!

This bug is similar to the make utility bug. Tabs are used as
separator
in "make", and the makefile will not work if they are substituted by
spaces!

This makes every novice spend hours trying to find out why two
makefiles that look the
same do not work.

[Dan Pop]

In <pa************ *************** *@lightspeed.bc .ca> Kelsey Bjarnason <ke*****@lights peed.bc.ca> writes:

On Mon, 24 Nov 2003 16:52:07 -0800, Darius Fatakia wrote:

I seem to be having trouble with some of my math functions (pow, sqrt,
acos). They're the only ones I use in my code and they prevent the program
from compiling. I get a "undefined reference to 'pow'" error. Here is the
relevant portion of my code.

Sounds like a linker error - are you linking the math libraries? There's
a certain, popular compiler, especially widely used in the Linux world,
which has the terminally brain-dead habit of not including the math
libraries by default. Assuming you're using this compiler, try something
like this:

gcc -lm file.c

gcc merely follows the common Unix convention, established by a certain
Dennis M. Ritchie.

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Da*****@ifh.de

[Dan Pop]

In <bp**********@n ews-reader3.wanadoo .fr> "jacob navia" <ja***@jacob.re mcomp.fr> writes:

I wonder how many HUNDREDS of times I have seen this question
pop up.

Are there any gcc fans out here?
Why should gcc behave differently than most other Unix compilers?
Wouldn't it be time to include that library as a default library????

Nope, but it would be high time to include the contents of libm.a into
libc.a and provide an empty libm.a, for backward compatibility purposes.
The *good* reasons for keeping it separate have no longer been valid for
the last 15 years or so.

Which has precisely zilch to do with gcc or any other Unix compiler.

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Da*****@ifh.de

[Mark McIntyre]

On Tue, 25 Nov 2003 10:51:38 +0100, in comp.lang.c , "jacob navia"
<ja***@jacob.re mcomp.fr> wrote:

I wonder how many HUNDREDS of times I have seen this question
pop up.

thats why its a FAQ....

--
Mark McIntyre
CLC FAQ <http://www.eskimo.com/~scs/C-faq/top.html>
CLC readme: <http://www.angelfire.c om/ms3/bchambless0/welcome_to_clc. html>

[Mark McIntyre]

On Mon, 24 Nov 2003 16:52:07 -0800, in comp.lang.c , "Darius Fatakia"
<da************ @yahoo.com> wrote:

"undefined reference to 'pow'" error.

This is a FAQ. Please read the FAQs

--
Mark McIntyre
CLC FAQ <http://www.eskimo.com/~scs/C-faq/top.html>
CLC readme: <http://www.angelfire.c om/ms3/bchambless0/welcome_to_clc. html>

[Joe Wright]

jacob navia wrote:

[ snip ] This bug is similar to the make utility bug. Tabs are used as
separator
in "make", and the makefile will not work if they are substituted by
spaces!

This makes every novice spend hours trying to find out why two
makefiles that look the
same do not work.

I'm not sure I agree that it's a bug but it is annoying. make simply
uses TAB as a separator between the Rule and the Command portions of a
statement. As I use edit.com with tabs set to 3 this annoyed the hell
out of me too. Reading the info file on make one day (I'm surprised how
little I do this and how much I should) I read that ';' semicolon is
also a Rule / Command separator. How 'bout this..

# Use GNU make to build an executable for testing GE.

cc=gcc
obj=ge.o main.o
exe=main.exe
opt=-W -Wall -ansi -pedantic -O2 -c

# Note that semicolon (not TAB) separates Rule from Command on a line.

$(exe) : $(obj) ; $(cc) -s $(obj) -o $(exe)
ge.o : ge.c ; $(cc) $(opt) ge.c
main.o : main.c ge.h ; $(cc) $(opt) main.c

Live and learn.
--
Joe Wright http://www.jw-wright.com
"Everything should be made as simple as possible, but not simpler."
--- Albert Einstein ---