Compile the program using gcc -o timing1 timing1.c -lm. Run the program 10 times with a command line argument of 5000000. Report the timings observed in the output. Repeat the process with arguments 10000000 and 20000000. Discuss the results observed, in particular regarding the resolution of the timing procedure used and the reproducibility of the results between runs. From the observed results, estimate the time needed to compute a square root.
Compile the program using gcc -o timing1 timing1.c -lm. Run the program 10 times with a command line argument of 5000000. Report the timings observed in the output. Repeat the process with arguments 10000000 and 20000000. Discuss the results observed, in particular regarding the resolution of the timing procedure used and the reproducibility of the results between runs. From the observed results, estimate the time needed to compute a square root.
Database System Concepts
7th Edition
ISBN:9780078022159
Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Chapter1: Introduction
Section: Chapter Questions
Problem 1PE
Related questions
Question
Compile the
Run the program 10 times with a command line argument of 5000000. Report the timings observed in the output. Repeat the process with arguments 10000000 and 20000000.
Discuss the results observed, in particular regarding the resolution of the timing procedure used and the reproducibility of the results between runs. From the observed results,
estimate the time needed to compute a square root.
![```c
/*
* timing1.c: test timing functions
*/
#include "stdio.h"
#include "time.h"
#include "sys/time.h"
#include "math.h"
#include "stdlib.h"
volatile double gtod(void)
{
static struct timeval tv;
static struct timezone tz;
gettimeofday(&tv,&tz);
return tv.tv_sec + 1.e-6*tv.tv_usec;
}
int main(int argc, char** argv)
{
int n = atoi(argv[1]);
clock_t clk;
double t, t_cpu, t_real;
clk = clock();
t = gtod();
/* do something */
double sum = 0.0;
int i;
for (i = 0; i < n; i++)
sum += sqrt((double) i);
long long delta_clock = clock() - clk;
t_cpu = ((double) delta_clock) / CLOCKS_PER_SEC;
t_real = gtod() - t;
printf(" clock: %15lld \n", delta_clock );
printf(" t cpu: %15.6f s\n", t_cpu );
printf(" t real: %15.6f s\n", t_real );
}
```
### Explanation
This C program benchmarks the execution time of a series of computations, specifically the summation of square roots. The code includes timing functionality to record both CPU time and real time.
- **Header Files**:
- `<stdio.h>` and `<stdlib.h>` for input/output operations and standard library functions.
- `<time.h>` and `<sys/time.h>` for accessing timing functions.
- `<math.h>` for mathematical computations.
- **Function `gtod()`**: This function returns the current time in seconds with microsecond precision using `gettimeofday`.
- **`main()` Function**:
- Takes the number of iterations `n` from the command line argument.
- Initializes variables for storing clock time and real time.
- Records the CPU clock and real time before starting computations.
- Executes a loop summing the square roots of numbers from 0 to `n-1`.
- Calculates the elapsed CPU cycles using `clock()` and the elapsed real time using `gtod()`.
- Results are printed for:
- `clock`: The number of clock cycles elapsed.
- `t cpu`: CPU time taken in seconds.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F58c96cd7-9b6a-41da-9e63-20673950e6d6%2Ff46af45f-8934-41ce-8df6-c6eea7aad353%2Fjgxyi8n_processed.png&w=3840&q=75)
Transcribed Image Text:```c
/*
* timing1.c: test timing functions
*/
#include "stdio.h"
#include "time.h"
#include "sys/time.h"
#include "math.h"
#include "stdlib.h"
volatile double gtod(void)
{
static struct timeval tv;
static struct timezone tz;
gettimeofday(&tv,&tz);
return tv.tv_sec + 1.e-6*tv.tv_usec;
}
int main(int argc, char** argv)
{
int n = atoi(argv[1]);
clock_t clk;
double t, t_cpu, t_real;
clk = clock();
t = gtod();
/* do something */
double sum = 0.0;
int i;
for (i = 0; i < n; i++)
sum += sqrt((double) i);
long long delta_clock = clock() - clk;
t_cpu = ((double) delta_clock) / CLOCKS_PER_SEC;
t_real = gtod() - t;
printf(" clock: %15lld \n", delta_clock );
printf(" t cpu: %15.6f s\n", t_cpu );
printf(" t real: %15.6f s\n", t_real );
}
```
### Explanation
This C program benchmarks the execution time of a series of computations, specifically the summation of square roots. The code includes timing functionality to record both CPU time and real time.
- **Header Files**:
- `<stdio.h>` and `<stdlib.h>` for input/output operations and standard library functions.
- `<time.h>` and `<sys/time.h>` for accessing timing functions.
- `<math.h>` for mathematical computations.
- **Function `gtod()`**: This function returns the current time in seconds with microsecond precision using `gettimeofday`.
- **`main()` Function**:
- Takes the number of iterations `n` from the command line argument.
- Initializes variables for storing clock time and real time.
- Records the CPU clock and real time before starting computations.
- Executes a loop summing the square roots of numbers from 0 to `n-1`.
- Calculates the elapsed CPU cycles using `clock()` and the elapsed real time using `gtod()`.
- Results are printed for:
- `clock`: The number of clock cycles elapsed.
- `t cpu`: CPU time taken in seconds.
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