Author Topic: Code::Blocks shows different result from other IDE's  (Read 819 times)

Offline marky1337

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Code::Blocks shows different result from other IDE's
« on: February 22, 2018, 12:34:53 am »
Hi, I'm trying to do a programming problem using Kruskal's minimum spanning tree algorithm but that's not so important, my problem is that Code::Blocks gives me a different result from every other IDE i could find. The result is wrong while other IDEs give me the right answer with the same code. I tried it on 2 computers, same thing. So, what's wrong?

Offline oBFusCATed

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Re: Code::Blocks shows different result from other IDE's
« Reply #1 on: February 22, 2018, 02:14:53 am »
http://wiki.codeblocks.org/index.php/FAQ-General

Most probably your code is wrong...  8)
(most of the time I ignore long posts)
[strangers don't send me private messages, I'll ignore them; post a topic in the forum, but first read the rules!]

Offline stahta01

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Re: Code::Blocks shows different result from other IDE's
« Reply #2 on: February 22, 2018, 02:29:48 am »
The main problem is you do not know the difference between an compiler and a IDE.

Tim S.
C Programmer working to learn more about C++ and Git.
On Windows 7 64 bit and Windows 10 32 bit.
On Debian Testing, compiling CB Trunk against wxWidgets 3.0.2.
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When in doubt, read the CB WiKi FAQ. http://wiki.codeblocks.org

Offline marky1337

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Re: Code::Blocks shows different result from other IDE's
« Reply #3 on: February 22, 2018, 12:53:52 pm »
http://wiki.codeblocks.org/index.php/FAQ-General

Most probably your code is wrong...  8)

I took the code from geeksforgeeks and with exactly the same code I got different results on their IDE and on Code::Blocks.
The code: https://www.geeksforgeeks.org/greedy-algorithms-set-2-kruskals-minimum-spanning-tree-mst/

The main problem is you do not know the difference between an compiler and a IDE.

Tim S.


Care to explain more? Don't just post-hunt.
« Last Edit: February 22, 2018, 12:59:37 pm by marky1337 »

Offline BlueHazzard

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Re: Code::Blocks shows different result from other IDE's
« Reply #4 on: February 22, 2018, 03:00:26 pm »
you give way to less information...
Give your operating system, your compiler, your compiler version, the other compiler version, codeblocks version, codeblocks installation file source
Quote
my problem is that Code::Blocks gives me a different result from every other IDE i could find
what are different results?
This "different" can vary from crashing, black output, gibberish output, to totally fine output but different representation... And any difference can have different reasons.... We can not help with this few informations. Describe more, no describe EXACTLY every detail you have...

Are you using debug builds? Release builds? Do you know what a compiler is? Do you use different compilers for every IDE? What are the others ide? what compilers do they use? What if you use the other compilers with codeblocks?

Can you post a full rebuild log?
http://wiki.codeblocks.org/index.php?title=FAQ-Compiling_(general)#Q:_How_do_I_report_a_compilation_problem_on_the_forums.3F

Quote
Care to explain more? Don't just post-hunt.
Well, two seconds google, or just 2 sec on wiki would solve this:
https://en.wikipedia.org/wiki/Integrated_development_environment
http://wiki.codeblocks.org/index.php/FAQ-General#Q:_What_is_Code::Blocks.3F
http://wiki.codeblocks.org/index.php/FAQ-General#Q:_What_Code::Blocks_is_not.3F


« Last Edit: February 22, 2018, 03:03:42 pm by BlueHazzard »

Offline marky1337

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Re: Code::Blocks shows different result from other IDE's
« Reply #5 on: February 22, 2018, 04:09:46 pm »
Thank you BlueHazzard for the good reply. I thought i souldn't exagerate with the information.
One computer has Windows XP SP3 32bit  ::) , one has Windows 10 64bit.
Both use Code::Blocks 16.01 (from codeblocks.org)  with MinGW 4.9.2.
The program compiles fine, the output is fine structurally, but it's wrong (on all of C++98/C++00/C++11), it should be a different one. I hope you understood what result i was talking about, it's the programming problem's answer.

Both the debug and the release mode output the same thing. I know what a compiler is (more or less). The other IDEs(which i now realise are more of a compiler than an IDE  ::) ) i used are some online ones.
Some links to some of them (idk if it's allowed):
https://www.onlinegdb.com/online_c++_compiler
https://www.codechef.com/ide
http://cpp.sh/
https://ide.geeksforgeeks.org/

My question is more like why would that happen as long as the code is absolutely the same?


Build log:
Quote
-------------- Clean: Release in wtfkruskal (compiler: GNU GCC Compiler)---------------


Cleaned "wtfkruskal - Release"


-------------- Build: Release in wtfkruskal (compiler: GNU GCC Compiler)---------------


mingw32-g++.exe -Wall -fexceptions -O2  -c "D:\code blocks\wtfkruskal\main.cpp" -o obj\Release\main.o
mingw32-g++.exe  -o bin\Release\wtfkruskal.exe obj\Release\main.o  -s 
Output file is bin\Release\wtfkruskal.exe with size 110.00 KB
Process terminated with status 0 (0 minute(s), 5 second(s))
0 error(s), 0 warning(s) (0 minute(s), 5 second(s))
 


« Last Edit: February 22, 2018, 04:25:30 pm by marky1337 »

Offline BlueHazzard

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Re: Code::Blocks shows different result from other IDE's
« Reply #6 on: February 22, 2018, 07:09:32 pm »
Quote
My question is more like why would that happen as long as the code is absolutely the same?
It does not happen. If i copy and paste the program from your link into a codeblocks project i get exactly the same output as in the link at the bottom. (but i use gcc 5.x.x)


Quote
The program compiles fine, the output is fine structurally, but it's wrong (on all of C++98/C++00/C++11), it should be a different one. I hope you understood what result i was talking about,
i still don't know what your output is....

[edit:] You can copy and paste the output of a console window. Google for it...

Offline marky1337

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Re: Code::Blocks shows different result from other IDE's
« Reply #7 on: February 22, 2018, 09:18:22 pm »
Quote
The program compiles fine, the output is fine structurally, but it's wrong (on all of C++98/C++00/C++11), it should be a different one. I hope you understood what result i was talking about,
i still don't know what your output is....

[edit:] You can copy and paste the output of a console window. Google for it...

The example from the site gives me a good output too but if i modify the input ( the graph ) a bit so the code will look like this (a bit long but i can't see a pop-up window in the text editor here and also i know i inserted the input by hand but i wanted the code to be as similar as the original ):
Code: [Select]
// C++ program for Kruskal's algorithm to find Minimum Spanning Tree
// of a given connected, undirected and weighted graph
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

// a structure to represent a weighted edge in graph
struct Edge
{
    int src, dest, weight;
};

// a structure to represent a connected, undirected
// and weighted graph
struct Graph
{
    // V-> Number of vertices, E-> Number of edges
    int V, E;

    // graph is represented as an array of edges.
    // Since the graph is undirected, the edge
    // from src to dest is also edge from dest
    // to src. Both are counted as 1 edge here.
    struct Edge* edge;
};

// Creates a graph with V vertices and E edges
struct Graph* createGraph(int V, int E)
{
    struct Graph* graph = new Graph;
    graph->V = V;
    graph->E = E;

    graph->edge = new Edge[E];

    return graph;
}

// A structure to represent a subset for union-find
struct subset
{
    int parent;
    int rank;
};

// A utility function to find set of an element i
// (uses path compression technique)
int find(struct subset subsets[], int i)
{
    // find root and make root as parent of i
    // (path compression)
    if (subsets[i].parent != i)
        subsets[i].parent = find(subsets, subsets[i].parent);

    return subsets[i].parent;
}

// A function that does union of two sets of x and y
// (uses union by rank)
void Union(struct subset subsets[], int x, int y)
{
    int xroot = find(subsets, x);
    int yroot = find(subsets, y);

    // Attach smaller rank tree under root of high
    // rank tree (Union by Rank)
    if (subsets[xroot].rank < subsets[yroot].rank)
        subsets[xroot].parent = yroot;
    else if (subsets[xroot].rank > subsets[yroot].rank)
        subsets[yroot].parent = xroot;

    // If ranks are same, then make one as root and
    // increment its rank by one
    else
    {
        subsets[yroot].parent = xroot;
        subsets[xroot].rank++;
    }
}

// Compare two edges according to their weights.
// Used in qsort() for sorting an array of edges
int myComp(const void* a, const void* b)
{
    struct Edge* a1 = (struct Edge*)a;
    struct Edge* b1 = (struct Edge*)b;
    return a1->weight > b1->weight;
}

// The main function to construct MST using Kruskal's algorithm
void KruskalMST(struct Graph* graph)
{
    int V = graph->V;
    struct Edge result[V];  // Tnis will store the resultant MST
    int e = 0;  // An index variable, used for result[]
    int i = 0;  // An index variable, used for sorted edges

    // Step 1:  Sort all the edges in non-decreasing
    // order of their weight. If we are not allowed to
    // change the given graph, we can create a copy of
    // array of edges
    qsort(graph->edge, graph->E, sizeof(graph->edge[0]), myComp);

    // Allocate memory for creating V ssubsets
    struct subset *subsets =
        (struct subset*) malloc( V * sizeof(struct subset) );

    // Create V subsets with single elements
    for (int v = 0; v < V; ++v)
    {
        subsets[v].parent = v;
        subsets[v].rank = 0;
    }

    // Number of edges to be taken is equal to V-1
    while (e < V - 1)
    {
        // Step 2: Pick the smallest edge. And increment
        // the index for next iteration
        struct Edge next_edge = graph->edge[i++];

        int x = find(subsets, next_edge.src);
        int y = find(subsets, next_edge.dest);

        // If including this edge does't cause cycle,
        // include it in result and increment the index
        // of result for next edge
        if (x != y)
        {
            result[e++] = next_edge;
            Union(subsets, x, y);
        }
        // Else discard the next_edge
    }

    // print the contents of result[] to display the
    // built MST
    printf("Following are the edges in the constructed MST\n");
    for (i = 0; i < e; ++i)
        printf("%d -- %d == %d\n", result[i].src, result[i].dest,
                                                 result[i].weight);
    return;
}

// Driver program to test above functions
int main()
{
    int V = 9;  // Number of vertices in graph
    int E = 14;  // Number of edges in graph
    struct Graph* graph = createGraph(V, E);

    graph->edge[0].src = 0;
    graph->edge[0].dest = 1;
    graph->edge[0].weight = 10;

    graph->edge[1].src = 0;
    graph->edge[1].dest = 2;
    graph->edge[1].weight = -11;

    graph->edge[2].src = 1;
    graph->edge[2].dest = 3;
    graph->edge[2].weight = 11;

    graph->edge[3].src = 1;
    graph->edge[3].dest = 4;
    graph->edge[3].weight = 11;

    graph->edge[4].src = 4;
    graph->edge[4].dest = 5;
    graph->edge[4].weight = 13;

    graph->edge[5].src = 2;
    graph->edge[5].dest = 3;
    graph->edge[5].weight = 10;

    graph->edge[6].src = 3;
    graph->edge[6].dest = 5;
    graph->edge[6].weight = 12;

    graph->edge[7].src = 3;
    graph->edge[7].dest = 6;
    graph->edge[7].weight = 5;

    graph->edge[8].src = 2;
    graph->edge[8].dest = 6;
    graph->edge[8].weight = 4;

    graph->edge[9].src = 2;
    graph->edge[9].dest = 7;
    graph->edge[9].weight = 5;

    graph->edge[10].src = 7;
    graph->edge[10].dest = 6;
    graph->edge[10].weight = 5;

    graph->edge[11].src = 7;
    graph->edge[11].dest = 8;
    graph->edge[11].weight = 4;

    graph->edge[12].src = 8;
    graph->edge[12].dest = 6;
    graph->edge[12].weight = 3;

    graph->edge[13].src = 5;
    graph->edge[13].dest = 6;
    graph->edge[13].weight = 11;
    KruskalMST(graph);

    return 0;
}

The output i get in Code::Blocks:
Quote
Following are the edges in the constructed MST
3 -- 6 == 5
0 -- 2 == -11
8 -- 6 == 3
7 -- 8 == 4
2 -- 3 == 10
0 -- 1 == 10
5 -- 6 == 11
1 -- 4 == 11

The output i get online which is the correct output:
Quote
Following are the edges in the constructed MST
0 -- 2 == -11
8 -- 6 == 3
2 -- 6 == 4
7 -- 8 == 4
3 -- 6 == 5
0 -- 1 == 10
1 -- 4 == 11
5 -- 6 == 11

So can you try the same code out and tell me which is the output you get? I used CB for 3 and a half years now and i never encountered this odd issue.
« Last Edit: February 22, 2018, 10:02:00 pm by marky1337 »

Offline BlueHazzard

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Re: Code::Blocks shows different result from other IDE's
« Reply #8 on: February 22, 2018, 11:21:05 pm »
Now we are talking.... See? You have wasted a whole day with writing non relevant post until we finally get some code to run and inspect.... Now we can work... This is so frustrating if people tell they run "this code" and the it comes out, that they modified it and it is completely different...

Now i get also your result. The first thing i am thinking of is the web based ides run all on linux and you and me are running windows.
They are running gcc 5.4, you are running gcc4.6, i am running gcc5.1, gcc 6.4 and mingw64-gcc7.1 on all this compiler on windows the result is the same.

Now lets look at the code, where is the possibility that something goes wrong? My first guess is "qsort"

i made a breakpoint after the function call.

on windows:
Code: [Select]
p graph->edge[0]
$1 = {src = 3, dest = 6, weight = 5}

p graph->edge[1]
$2 = {src = 0, dest = 2, weight = -11}

p graph->edge[2]
$3 = {src = 8, dest = 6, weight = 3}

on linux:
Code: [Select]
p graph->edge[0]                                                                                                     
$2 = {src = 0, dest = 2, weight = -11}
graph->edge[1]]                                                                                                     
$4 = {src = 8, dest = 6, weight = 3} 
p graph->edge[2]]                                                                                                     
$6 = {src = 2, dest = 6, weight = 4}

there is something fishy...  Just to make things clear, this is not a codeblocks problem, but a compiler, stdlib problem...
sorted list on linux:
Code: [Select]
0: -11                                                                                                                                                                                         
1: 3                                                                                                                                                                                           
2: 4                                                                                                                                                                                           
3: 4                                                                                                                                                                                           
4: 5                                                                                                                                                                                           
5: 5                                                                                                                                                                                           
6: 5                                                                                                                                                                                           
7: 10                                                                                                                                                                                         
8: 10                                                                                                                                                                                         
9: 11                                                                                                                                                                                         
10: 11                                                                                                                                                                                         
11: 11                                                                                                                                                                                         
12: 12                                                                                                                                                                                         
13: 13

sorted list in windows:
Code: [Select]
0: 5
1: -11
2: 3
3: 4
4: 5
5: 10
6: 5
7: 10
8: 4
9: 11
10: 11
11: 11
12: 12
13: 13

 :o

if i use this sort function:
Code: [Select]
    struct {
        bool operator()(const Edge a1,const Edge b1) const
        {
            return a1.weight < b1.weight;
        }
    } customLess;
    std::sort(graph->edge, graph->edge + graph->E, customLess);
all works as expected:

Code: [Select]
0 -- 2 == -11
8 -- 6 == 3
2 -- 6 == 4
7 -- 8 == 4
3 -- 6 == 5
0 -- 1 == 10
1 -- 4 == 11
5 -- 6 == 11

The question now is, why does qsort on windows does not work?....
« Last Edit: February 22, 2018, 11:34:25 pm by BlueHazzard »

Offline BlueHazzard

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Re: Code::Blocks shows different result from other IDE's
« Reply #9 on: February 22, 2018, 11:52:46 pm »
Ok, i know now what the problem is.... Read the documentation of qsort: http://en.cppreference.com/w/cpp/algorithm/sort
Quote
comparison function which returns ​a negative integer value if the first argument is less than the second,

a positive integer value if the first argument is greater than the second and zero if the arguments are equal.

your compare function does not fulfill this criteria...

It seems that the qsort implementation of windows needs exactly this behavior and linux is a bit more tolerant to this...

if i implement the compare function correctly all works as expected...

[Edit:] so obfuscated was right, your code was wrong :) Remember: This question is not in the scope of this forum, because it has nothing to do with the IDE codeblocks, but with the stdlib of c

« Last Edit: February 22, 2018, 11:55:26 pm by BlueHazzard »

Offline marky1337

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Re: Code::Blocks shows different result from other IDE's
« Reply #10 on: February 23, 2018, 12:20:15 am »
Ok, you made it clear now, this is the help I needed but I didn't know how and where to ask for it apparently ( my first thought was "Let's ask the guys on the Code::Blocks forum first"   ::) ), so thank you for your time BlueHazzard .
Thanks and sorry for not really respecting the forum's rules ( I realised too late  :-[).

Offline Krice

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Re: Code::Blocks shows different result from other IDE's
« Reply #11 on: February 26, 2018, 12:18:17 pm »
In addition with code like that the result can be anything. There is 'new' but no 'delete', and also there is malloc (and 'new' in the same code). It tells that you need to delete that code and never look at it again. I don't even want to talk about the "style" of naming variables etc.