Parallalization of matrix multiply error

[antepenultimate]

I'm tried to multiply 1000x1000 matrixes with segments. But I get an error..

#include "stdafx.h"
#include <Windows.h>
#include <stdio.h>
#include <iostream>
#include <process.h>
#include <stdlib.h>
#include <math.h>
#include <chrono>


volatile int str = 0;
const int size = 100;
const int BLM = 25;
int **A;//Matrix A
int **B;//Matrix B
int **C;//Output Matrix C
//int matriscarp(int, int);
//void matrisAtama();
//void destruct();

using namespace std;
void matrisAtama(){

//assigning first dimension
A = new int*[size];
//Assign second dimension
for (int i = 0; i < size; i++)
{
	A[i] = new int[size];
}
//assigning first dimension
B = new int*[size];
//Assign second dimension
for (int i = 0; i < size; i++)
{
	B[i] = new int[size];
}

//assigning first dimension
C = new int*[size];
//Assign second dimension
for (int i = 0; i < size; i++)
{
	C[i] = new int[size];
}

int l = 1, u = 1;
for (int i = 0; i < size; i++)
for (int j = 0; j < size; j++)
{
	l++;
	u++;
	l = l % 9;
	u = u % 9;
	A[i][j] = l;
	B[i][j] = u;
}

}
void destruct(){
	//delete the dynamic memory of A
	for (int i = 0; i < size; i++)
	{
		delete[] A[i];
	}
	delete[] A;
	//delete the dynamic memory of B
	for (int i = 0; i < size; i++)
	{
		delete[] B[i];
	}
	delete[] B;
	//delete the dynamic memory of C
	for (int i = 0; i < size; i++)
	{
		delete[] C[i];
	}
	delete[] C;
}

int matriscarp(int n, int p){

	//auto BslTimer = chrono::high_resolution_clock::now();

	for (int i = 0; i < size; i++)
	for (int j = 0; j < size; j++)
	{
		C[i][j] = 0; //initializing c to zero
	}


	for (int i = n; i < p; i++){
		cout << endl;
		for (int j = 0; j < size; j++)
		{
			for (int k = 0; k < size; k++){
				C[j][i] += A[j][k] * B[k][i];

			}
		}
	}
	for (int i = 0; i < size; i++){
		for (int j = 0; j < size; j++)
		{
			cout << C[i][j] << " ";

		}
	}
	/*auto BtsTimer = std::chrono::high_resolution_clock::now();
	auto sure = BtsTimer - BslTimer;
	printf("Total duration %5d \n", chrono::duration_cast<std::chrono::milliseconds>(sure).count());*/
	return 1;
}



unsigned int __stdcall fFonk(void*){

	auto BslTimer = chrono::high_resolution_clock::now(); //  zamanı başlat

	while (str < size) {
		int t_str;
		t_str = str; // şimdiki değerini al 
		str += BLM;      //ve sıradaki 250 taneyi coz
		matriscarp(t_str, t_str+BLM);
			// bulunan sayıları ekrana basabilirsiniz
			//printf("Thread  no %7d sayi = %8d asal mi = %s\n", GetCurrentThreadId(), j, s);
		 // her thread 200'li blokları hesaplar

	// her thread kendi süresini yazar
	auto BtsTimer = std::chrono::high_resolution_clock::now(); // bittikten sonra zamani oku
	auto sure = BtsTimer - BslTimer; /// farki hesapla
	printf("Toplam sure %5d ms\n", chrono::duration_cast<std::chrono::milliseconds>(sure).count());
	return 0;
}
}
int main(int argc, char* argv[]){
	HANDLE hndl1, hndl2, hndl3, hndl4;
	matrisAtama();

	hndl1 = (HANDLE)_beginthreadex(0, 0, &fFonk, (void*)0, 0, 0);
	hndl2 = (HANDLE)_beginthreadex(0, 0, &fFonk, (void*)0, 0, 0);
	hndl3 = (HANDLE)_beginthreadex(0, 0, &fFonk, (void*)0, 0, 0);
	hndl4 = (HANDLE)_beginthreadex(0, 0, &fFonk, (void*)0, 0, 0);

	WaitForSingleObject(hndl1, INFINITE);
	WaitForSingleObject(hndl2, INFINITE);
	WaitForSingleObject(hndl3, INFINITE);
	WaitForSingleObject(hndl4, INFINITE);

	CloseHandle(hndl1);
	CloseHandle(hndl2);
	CloseHandle(hndl3);
	CloseHandle(hndl4);
	destruct();
	getchar();
	return 0;
}

This is the error i got: Warning 1 warning C4715: 'fFonk' : not all control paths return a value c:\users\consium nullum\documents\visual studio 2013\projects\d3d11_chess\d3d11_chess\xaa\xaa\xaa.cpp 137 1 xaa

[2kaud]

The warning is correct. If the function is indented

unsigned int __stdcall fFonk(void*)
{
	auto BslTimer = chrono::high_resolution_clock::now(); //  zamanı başlat

	while (str < size) {
		int t_str;
		t_str = str; // şimdiki değerini al 
		str += BLM;      //ve sıradaki 250 taneyi coz
		matriscarp(t_str, t_str+BLM);
			// bulunan sayıları ekrana basabilirsiniz
			//printf("Thread  no %7d sayi = %8d asal mi = %s\n", GetCurrentThreadId(), j, s);
                        // her thread 200'li blokları hesaplar

	               // her thread kendi süresini yazar
	        auto BtsTimer = std::chrono::high_resolution_clock::now(); // bittikten sonra zamani oku
	        auto sure = BtsTimer - BslTimer; /// farki hesapla
	        printf("Toplam sure %5d ms\n", chrono::duration_cast<std::chrono::milliseconds>(sure).count());
	        return 0;
       }

//missing return value here

}

When the while loop terminates when str >= size, the function does not return a value. Should the return 0 statement be outside of the while loop?