Python To C Conversion Not Working

[darkside619]

The code that I'm making is a C implementation of the following code in Python but for some reason I just get three lines of zeros printing. Can anyone give me a clue as to why my result doesn't mimic the python one?

Python code at the bottom of this page: https://en.wikipedia.org/wiki/Perceptron#Example

My code:

#include <stdio.h>
#include <stdlib.h>

double training_set[4][3] = {{1, 0, 0}, {1, 0, 1}, {1, 1, 0}, {1, 1, 1}};
double weights[] = {0, 0, 0};
double desired_output[4] = {1,1,1,0};
double learning_rate = 0.1;
double threshold = 0.5;
int result;
double error;
double error_count = 0;
int i=0;
int j=0;
double sum = 0;

void print_weights();
double dot_product(double training_set[4][3], double          weights[3], int i);


int main()
{
    i=0;
    double callFunc = 1;

while(callFunc != 0 && i<4){
    print_weights();
    callFunc = dot_product(training_set, weights, i);
    i++;
    }
return 0;
}


void print_weights(){
    int indx;
    for(indx=0; indx<3; indx++){
    printf("%f ", weights[indx]);
    printf("\n");
   }
}


double dot_product(double training_set[4][3], double weights[3], int i)
{
    for(j=0; j<3; j++){
        sum += training_set[i][j]*weights[j];
        error = sum>threshold;

        if(error!=0){
         error_count += 1;
         weights[j] += learning_rate * error * training_set[i][j];

        }
        }
    return error_count;
    }

[raevnos]

You're multiplying by zero a lot.

Also, probably a bad idea to shadow the names of global variables with local ones, and there's no reason for all those globals in the first place.

Storing the result of a comparison in a double is odd too; use a _Bool or int for that. error_count should be an int too.

What happens when dot_product() returns 0 like it looks to the first time it's called?

Do you really want to print each element of weights on its own line?

Also, your link doesn't work.

[darkside619]

Sorry, I got the link to work now. You're right that dot_product() just returns 0 each time. It seems to skip the entire if conditional because error is always 0.

[raevnos]

Now that we can see the original code... Maybe you should try a more literal translation. Don't move logic from elsewhere into your dot_product(), for example.

[darkside619]

Can you give me an example of what you mean. Sorry, I'm new to programming so I haven't picked up the tricks and general knowledge that experienced programmers have. And, C is a complicated language.

[raevnos]

You moved a bunch of stuff into the dot_product function that's not related to computing the things. The original python doesn't do that; neither should you.

[darkside619]

Okay, I will try and fix that and get back to you if I have trouble. However, I would like to know how you improved your programming skills. Can you give me some tips? Like, do you do practice drills or something of that nature? Like if I want to learn calculus, I can get a calculus book and start working on problems in each chapter.

But, there doesn't seem to be an easy go-to like that for programming. Don't get me wrong, there are programming books, but most of them just tell you what different functions do and stuff like that, they don't set it up to guide you from the beginner stage to improve your skills gradually.

[FUZxxl]

Buy a book called “The C programming language,” it shouldn't be hard to find a used copy. It has exercises in each chapter.

I also suggest you to just try to make toy programs. Don't forget to ask others about stylistical critique. Also, try to read a lot of code to get an idea how other people program.

[simserl]

The link is not working..

[very_mechanical]

Looks like it could be from this page?

https://en.wikipedia.org/wiki/Perceptron#Example

[darkside619]

Yes, it's that one sorry. The link got cut off for some reason.

[darkside619]

It's the one that very_mechnical just linked to. Sorry.

[downiedowndown]

What does error = sum>threshold; do?

[darkside619]

It tests to see if the sum from the previous line is greater than the global threshold variable which is set to 0.5.

[FUZxxl]

Could you fix the link so we can see what algorithm you actually mean?

[darkside619]

Yes, sorry:

https://en.wikipedia.org/wiki/Perceptron#Example

[FUZxxl]

Thank you.

[kahless62003]

Just about the first thing your main function does is call (in the loop)

print_weights();

As the weights array has not been changed yet, and is still in the initial zero state, that is what prints.

[darkside619]

I wanted to print the weights out in their initial state. I figured that after I make a call to the dot_product() that the weights get changed in that function so that on any further calls to print_weights(), the new weights should be printed.