Q1:

// creates a new matrix from a group of consecutive rows of an old one

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

int onedim(int row, int col, int nCols) { return row * nCols + col; }

// copies nRowsSubM consecutive rows of m to subMat, starting with 
// row firstRow in m; m is nRowsM by nColsM

int *getRows(int *m, int nRowsM, int nColsM, int firstRow, int nRowsSubM) {
   int *subMat = malloc(nRowsSubM * nColsM * sizeof(int));
   #pragma omp parallel
   {  int *startFrom,*startTo,i;

      #pragma omp for
      for (int i = 0; i < nRowsSubM; i++) {
         startFrom = m + onedim(firstRow+i,0,nColsM);
         startTo = subMat + onedim(i,0,nColsM);
         memcpy(startTo, startFrom, nColsM * sizeof(int));
      }
   }
   return subMat;
}

int main() {
   // intended as a 4x3 matrix
   int z[12] = {5,12,13,6,2,22,15,3,1,2,3,4};
   omp_set_num_threads(2);
   // extract the last 2 cols
   int *outM = getRows(z,4,3,1,2);
   // should print
   //  6  2  22
   // 15  3   1
   for (int i = 0; i < 2; i++) {
      printf("%d %d %d\n",outM[3*i],outM[3*i+1],outM[3*i+2]);
   }
}