function call wont work multiple times, C/C++ on Raspbian

Question

I am having problems in this C/C++ program I wrote for the Raspberry Pi in Raspbian. Here is the link to download the cpp file UltraSonicTest.cpp:

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

int trigger = 4; //GPIO pin 23
int echo = 5;    //GPIO pin 24

double readValue();
void continuousRead();

int main(){

  printf("Raspberry Pi Sonar Test\n");

  if (wiringPiSetup() == -1)
    return 1;

  printf("WiringPi Setup Successful\n");

  pinMode(trigger, OUTPUT);
  pinMode(echo, INPUT);

  digitalWrite(trigger, 0); //GPIO pin 23 in the off position

  for (int i=0; i<10; i++){
    printf("Calling ContinuousRead\n");
    continuousRead();
  }

  return 0;
}

double readValue(){
  printf("Entering ReadValue...");
  double start=0, end=0, elapsed=0, distance=0;
  struct timespec gettime_now;
  // Send 10us pulse to trigger
  digitalWrite(trigger, 1);
  delayMicroseconds(0.00001);
  digitalWrite(trigger, 0);
  clock_gettime(CLOCK_REALTIME, &gettime_now);
  start = gettime_now.tv_nsec;

  while (digitalRead(echo)==0){
    clock_gettime(CLOCK_REALTIME, &gettime_now);
    start = gettime_now.tv_nsec;
  }

  while (digitalRead(echo)==1){
    clock_gettime(CLOCK_REALTIME, &gettime_now);
    end = gettime_now.tv_nsec;
  }

  elapsed = (end-start);

  //printf("Start: %lf\n", start);
  //printf("Stop: %lf\n", end);
  //printf("Time in milliseconds: %lf\n", elapsed/1000000);
  //printf("Elapsed: %lf seconds\n", elapsed = elapsed/1000000000);
  elapsed = elapsed/1000000000;
  //printf("%lf seconds * 34029 cm = %lf cm/s\n", elapsed, distance = elapsed*34029);
  distance = elapsed*34029;
  //printf("Distance = %lf cm\n",distance = distance/2);
  distance = distance/2;
  //printf("%lf cm = %lf inches\n",distance, distance/2.54);

  printf("Leaving ReadValue\n");
  return distance;
}

void continuousRead(){
  printf("..Starting ContinuousRead..");
  delay(1000);
  printf("Calling ReadValue\n");
  double distance= readValue();
  printf("Distance: %lf cm \n", distance);
}

I have the function call being called multiple times in a for loop, but the call only goes through 1-3 times.

sudo ./a.out  
Raspberry Pi Sonar Test  
WiringPi Setup Successful  
Calling ContinuousRead  
..Starting ContinuousRead..Calling ReadValue  
Entering ReadValue...Leaving ReadValue  
Distance: 2.194802 cm  
Calling ContinuousRead  
..Starting ContinuousRead..Calling ReadValue

Any idea what I'm doing wrong?

Answer 1

From the comment from nonsensickle!
delayMicroseconds(0.00001);
seems to have slowed down performance and and other side effects. changed to delay(1);
now the speed is acceptable. and it goes through the whole loop now.