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Loading vector with bit matrices

miamidawgs (42)
I have a code segment here that loads zeroes into a vector that represents a bit matrix. When the program runs and tries to write the result in a output file I get a seg fault. The program runs fine when it does not write in the output file.
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Bitmatrix::Bitmatrix(int rows, int cols)
{
    int count = 0;                                                                          // count variable
    int count2 = 0;                                                                        // 2nd count variable

    if( rows <= 0 || cols <= 0 )
    {
        fprintf( stderr, "Value of rows or columns is less than or equal to zero\n" );  // print error message
        M.resize( 1 );                                                                 // resize to 1 x 1 matrix
        M[0] = '0';                                                                   // set 0 as the value
    }
    else
        M.resize( rows );                                                           // resize matrix to number of rows
        for( count = 0; count < M.size(); count++ )
        {
            for( count2 = 0; count2 < cols; count2++ )
            {
                M[count].push_back( '0' );                                       // fill matrix with zeros  
            }
        }
}


The function that prints in the output file is:
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void Bitmatrix::Write(string fn)
{
    ofstream out;                                                      // output stream object
    int count = 0;                                                    // count variable
    int count2 = 0;                                                  // 2nd count variable

    out.open( fn.c_str() );                                        // open output file
    for( count = 0; count < M.size(); count++ )
    {
        for( count2 = 0; count2 < M[count].size(); count++ )
        {
            out << M[count][count2];
        }
        out << endl;
    }
}


Can anyone see why this is happening?
Last edited on
SakurasouBusters (732)
This may not help you much, but you did not close the file when you are done writing.
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void Bitmatrix::Write(string fn)
{
    ofstream out;                                                      // output stream object
    int count = 0;                                                    // count variable
    int count2 = 0;                                                  // 2nd count variable

    out.open( fn.c_str() );                                        // open output file
    for( count = 0; count < M.size(); count++ )
    {
        for( count2 = 0; count2 < M[count].size(); count++ )
        {
            out << M[count][count2];
        }
        out << endl;
    }
    out.close();
}
miamidawgs (42)
Thanks for pointing that out and no it did not stop the seg fault. Any clue on why its happening?
SakurasouBusters (732)
A pretty clear logic error there.
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    if( rows <= 0 || cols <= 0 )
    {
        fprintf( stderr, "Value of rows or columns is less than or equal to zero\n" );  // print error message
        M.resize( 1 );                                                                 // resize to 1 x 1 matrix
        M[0] = '0';                                                                   // set 0 as the value
    }
    else
        M.resize( rows );                                                           // resize matrix to number of rows
        for( count = 0; count < M.size(); count++ )
        {
            for( count2 = 0; count2 < cols; count2++ )
            {
                M[count].push_back( '0' );                                       // fill matrix with zeros  
            }
        }


Should be : 
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    if( rows <= 0 || cols <= 0 )
    {
        fprintf( stderr, "Value of rows or columns is less than or equal to zero\n" );  // print error message
        M.resize( 1 );                                                                 // resize to 1 x 1 matrix
        M[0] = '0';                                                                   // set 0 as the value
    }
    else
    {
        M.resize( rows );                                                           // resize matrix to number of rows
        for( count = 0; count < M.size(); count++ )
        {
            for( count2 = 0; count2 < cols; count2++ )
            {
                M[count].push_back( '0' );                                       // fill matrix with zeros  
            }
        }
    }
miamidawgs (42)
Is the change just brackets around the else block because that does not help the problem.
SakurasouBusters (732)
I did not say that would fix your problem.
Anyways, can you post your whole Bitmatrix class (and your function main() if possible)? I need more information.
miamidawgs (42)
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#include <string>
#include <iostream>
#include <vector>
using namespace std;

class Bitmatrix {
  public:
    Bitmatrix(string fn);            // Read from a file
    Bitmatrix(int rows, int cols);   // Create an empty bitmatrix
    void Print(int w);               // Print it on standard ouptput with spaces & blank lines 
    void Write(string fn);           // Write it to a file either as hex or zeros & ones
    void PGM(string fn, int pixels, int border);  // Write it to a pgm file 
    int Rows();
    int Cols();
    void Set(int row, int col, char val); // Set the specified element to val
    char Val(int row, int col);           // Return the specified element
    void Swap_Rows(int r1, int r2);
    void R1_Plus_Equals_R2(int r1, int r2);
    Bitmatrix *Copy();
  protected:
    vector <string> M; // The matrix.  Elements are '0' or '1'.
};
miamidawgs (42)
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main(int argc, char **argv)
{
  Bitmatrix *bm, *bm2, *bm3, *bm4, *bm5;
  BM_Hash *ht;
  int i, r, c, w, v, p, b;
  string s;
  vector <string> sv;
  istringstream ss;
  string prompt = "";
  HTVec all;
  vector <int> ind;

  if (argc > 2) {
    cerr << "usage: matrix_editor [prompt]\n";
    exit(1);
  }
  if (argc == 2) prompt = argv[1];
  if (prompt.size() > 0) prompt += " ";
  bm = NULL;

  ht = new BM_Hash(10000);
  while (1) {

    cout << prompt;
    cout.flush();

    if (!getline(cin, s)) exit(0);
    sv = StoSVec(s);
    if (sv.size() > 0 && sv[0][0] != '#') {
      if (sv[0] == "EMPTY") {
        if (sv.size() != 3 || sscanf(sv[1].c_str(), "%d", &r) != 1 || r <= 0 ||
                              sscanf(sv[2].c_str(), "%d", &c) != 1 || c <= 0) {
          printf("Should be: EMPTY rows cols\n");
        } else {
          if (bm != NULL) delete bm;
          bm = new Bitmatrix(r, c);
           }
      } else if (sv[0] == "SET") {
        if (sv.size() != 4 || sscanf(sv[1].c_str(), "%d", &r) != 1 || r < 0 ||
                              sscanf(sv[2].c_str(), "%d", &c) != 1 || c < 0 ||
                              (sv[3] != "0" && sv[3] != "1")) {
          printf("Should be: SET r c 0|1\n");
        } else if (bm == NULL) {
          printf("No current matrix.\n");
        } else if (r >= bm->Rows()) {
          printf("r must be less than %d\n", bm->Rows());
        } else if (c >= bm->Cols()) {
          printf("c must be less than %d\n", bm->Cols());
        } else {
          bm->Set(r, c, sv[3][0]);
        }
      } else if (sv[0] == "VAL") {
        if (sv.size() != 3 || sscanf(sv[1].c_str(), "%d", &r) != 1 || r < 0 ||
                              sscanf(sv[2].c_str(), "%d", &c) != 1 || c < 0) {
          printf("Should be: VAL r c\n");
        } else if (bm == NULL) {
          printf("No current matrix.\n");
        } else if (r >= bm->Rows()) {
          printf("r must be less than %d\n", bm->Rows());
        } else if (c >= bm->Cols()) {
          printf("c must be less than %d\n", bm->Cols());
        } else {
          printf("%d\n", bm->Val(r, c));
        }
      } else if (sv[0] == "SWAP") {
        if (sv.size() != 3 || sscanf(sv[1].c_str(), "%d", &r) != 1 || r < 0 ||
                              sscanf(sv[2].c_str(), "%d", &c) != 1 || c < 0) {
          printf("Should be: SWAP r1 r2\n");
        } else if (bm == NULL) {
          printf("No current matrix.\n");
        } else if (r >= bm->Rows()) {
          printf("r must be less than %d\n", bm->Rows());
         } else if (c >= bm->Rows()) {
          printf("c must be less than %d\n", bm->Rows());
        } else {
          bm->Swap_Rows(r, c);
        }
      } else if (sv[0] == "+=") {
        if (sv.size() != 3 || sscanf(sv[1].c_str(), "%d", &r) != 1 || r < 0 ||
                              sscanf(sv[2].c_str(), "%d", &c) != 1 || c < 0) {
          printf("Should be: R1+=R2 r1 r2\n");
        } else if (bm == NULL) {
          printf("No current matrix.\n");
        } else if (r >= bm->Rows()) {
          printf("r must be less than %d\n", bm->Rows());
        } else if (c >= bm->Rows()) {
          printf("c must be less than %d\n", bm->Rows());
        } else {
          bm->R1_Plus_Equals_R2(r, c);
        }
      } else if (sv[0] == "PRINT") {
        w = -1;
        if (sv.size() == 1) {
          w = 0;
        } else if (sv.size() != 2 || sscanf(sv[1].c_str(), "%d", &w) != 1 || w < 0) {
          printf("Should be: PRINT [w]\n");
          w = -1;
        }
        if (w >= 0) {
          if (bm == NULL) {
            printf("No current matrix.\n");
          } else {
            bm->Print(w);
          }
        }
      } else if (sv[0] == "WRITE") {
        if (sv.size() != 2) {
          printf("Should be: WRITE filename\n");
          } else if (bm == NULL) {
          printf("No current matrix.\n");
        } else {
          bm->Write(sv[1]);
        }
      } else if (sv[0] == "PGM") {
        if (sv.size() != 4) {
          printf("Should be: PGM filename pixels border\n");
        } else if (sscanf(sv[2].c_str(), "%d", &p) == 0 || p <= 0) {
          printf("Should be: PGM filename pixels border -- pixels > 0\n");
        } else if (sscanf(sv[3].c_str(), "%d", &b) == 0 || b < 0) {
          printf("Should be: PGM filename pixels border -- border >= 0\n");
        } else {
          bm->PGM(sv[1], p, b);
        }
      } else if (sv[0] == "READ") {
        if (sv.size() != 2) {
          printf("Should be: WRITE filename\n");
        } else {
          if (bm == NULL) delete bm;
          bm = new Bitmatrix(sv[1]);
        }
      } else if (sv[0] == "STORE") {
        if (sv.size() != 2) {
          printf("Should be: STORE key\n");
        } else {
          bm2 = ht->Recall(sv[1]);
          if (bm2 != NULL) delete bm2;
          ht->Store(sv[1], bm->Copy());
        }
      } else if (sv[0] == "RECALL") {
        if (sv.size() != 2) {
          printf("Should be: RECALL key\n");
        } else {
          bm2 = ht->Recall(sv[1]);
          if (bm2 == NULL) {
           printf("No matrix with key %s\n", sv[1].c_str());
          } else {
            if (bm != NULL) delete bm;
            bm = bm2->Copy();
          }
        }
      } else if (sv[0] == "ALL") {
        if (sv.size() != 1) {
          printf("Should be: ALL\n");
        } else {
          all = ht->All();
          for (i = 0; i < all.size(); i++) {
            printf("%-30s %3d X %3d\n", all[i]->key.c_str(), all[i]->bm->Rows(), all[i]->bm->Cols());
          }
        }
      } else if (sv[0] == "SUM") {
        if (sv.size() != 3) {
          printf("Should be: SUM key1 key2\n");
        } else {
          bm2 = ht->Recall(sv[1]);
          bm3 = ht->Recall(sv[2]);
          if (bm2 == NULL) {
            printf("No matrix %s\n", sv[1].c_str());
          } else if (bm3 == NULL) {
            printf("No matrix %s\n", sv[2].c_str());
          } else if (bm2->Rows() != bm3->Rows()) {
            printf("Rows don't match\n");
          } else if (bm2->Cols() != bm3->Cols()) {
            printf("Cols don't match\n");
          } else {
            if (bm != NULL) delete bm;
            bm4 = bm2->Copy();
            bm5 = bm3->Copy();
            bm = Sum(bm2, bm3);
            check_equal(bm2, bm4);
            check_equal(bm3, bm5);
             delete bm4;
            delete bm5;
          }
        }
      } else if (sv[0] == "PRODUCT") {
        if (sv.size() != 3) {
          printf("Should be: PRODUCT key1 key2\n");
        } else {
          bm2 = ht->Recall(sv[1]);
          bm3 = ht->Recall(sv[2]);
          if (bm2 == NULL) {
            printf("No matrix %s\n", sv[1].c_str());
          } else if (bm3 == NULL) {
            printf("No matrix %s\n", sv[2].c_str());
          } else if (bm2->Cols() != bm3->Rows()) {
            printf("Dimensions don't match\n");
          } else {
            bm4 = bm2->Copy();
            bm5 = bm3->Copy();
            if (bm != NULL) delete bm;
            bm = Product(bm2, bm3);
            check_equal(bm2, bm4);
            check_equal(bm3, bm5);
            delete bm4;
            delete bm5;
          }
        }
      } else if (sv[0] == "SUBMATRIX") {
        if (sv.size() < 2) {
          printf("Should be: SUBMATRIX rows...\n");
        } else if (bm == NULL) {
          printf("No matrix %s\n", sv[1].c_str());
        } else {
          ind.clear();
          for (i = 1; i < sv.size(); i++) {
            if (sscanf(sv[i].c_str(), "%d", &r) != 1 || r < 0 || r >= bm->Rows()) {
               printf("Bad row %s. Should be a number between 0 and %d\n",
                sv[i].c_str(), bm->Rows()-1);
              i = sv.size() + 10;
            } else {
              ind.push_back(r);
            }
          }
          if (i == sv.size()) {
            bm3 = bm->Copy();
            bm2 = Sub_Matrix(bm, ind);
            check_equal(bm, bm3);
            delete bm3;
            delete bm;
            bm = bm2;
          }

The end is cut off because its too long which is why I was hesitant to post at first
SakurasouBusters (732)
What is your assignment all about?
miamidawgs (42)
It loads bit matrices in a vector that stores only ones and zeroes. It is supposed to create, read, write, and manipulate the matrix. It also has another class that stores the matrices in a hash table( I have not started on that yet).
mbozzi (3910)
Did you miss the correction SakurasaoBusters offered in void Bitmatrix::Write(string) -- check the inner loop, line 10 of your code snippet?
miamidawgs (42)
I did. I don't see any correction for that function. Can you please elaborate?
SakurasouBusters (732)
Why are you using printf, sscanf, scanf, fprintf etc? That is C code style.
They are not type-safe and I recommend not using any of them.
Last edited on
miamidawgs (42)
That's what I was taught. Sometimes it is easier to format with them.
MikeyBoy (5631)
In your Write() method:

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    for( count = 0; count < M.size(); count++ )
    {
        for( count2 = 0; count2 < M[count].size(); count++ )
        {
            out << M[count][count2];
        }
        out << endl;
    }


in the inner loop, you're incrementing the wrong variable.
Last edited on
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