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A task is a logical unit of work performed by a particular thread. Tasks can nest; thus, tasks typically correspond to functions, scopes, or a case block in a switch statement. You can use the Task API to assign tasks to threads.
Task API is a per-thread function that works in resumed state. This function does not work in paused state.
The Task API does not enable a thread to suspend the current task and switch to a different task (task switching), or move a task to a different thread (task stealing).
A task instance represents a piece of work performed by a particular thread for a period of time. The task is defined by the bracketing of __itt_task_begin() and __itt_task_end() on the same thread.
Use This Primitive |
To Do This |
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void __itt_task_begin (const __itt_domain *domain,__itt_id taskid, __itt_id parentid, __itt_string_handle *name) |
Create a task instance on a thread. This becomes the current task instance for that thread. A call to __itt_task_end() on the same thread ends the current task instance. Parameters:
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void __itt_task_end (const __itt_domain *domain) |
Traces the end of the current task.
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To be able to see user tasks in your results, enable the Analyze user tasks checkbox in analysis settings.
The following table defines the parameters used in the Task API primitives.
Parameter |
Description |
|---|---|
__itt_domain |
The domain of the task. |
__itt_id taskid |
This is a reserved parameter. |
__itt_id parentid |
This is a reserved parameter. |
__itt_string_handle |
The task string handle. |
The following steps are required to begin using task APIs:
The following code snippet creates a domain and a couple of tasks at global scope.
#include "ittnotify.h"
void do_foo(double seconds);
__itt_domain* domain = __itt_domain_create("MyTraces.MyDomain");
__itt_string_handle* shMyTask = __itt_string_handle_create("My Task");
__itt_string_handle* shMySubtask = __itt_string_handle_create("My SubTask");
void BeginFrame() {
__itt_task_begin(domain, __itt_null, __itt_null, shMyTask);
do_foo(1);
}
void DoWork() {
__itt_task_begin(domain, __itt_null, __itt_null, shMySubtask);
do_foo(1);
__itt_task_end(domain);
}
void EndFrame() {
do_foo(1);
__itt_task_end(domain);
}
int main() {
BeginFrame();
DoWork();
EndFrame();
return 0;
}
#ifdef _WIN32
#include <ctime>
void do_foo(double seconds) {
clock_t goal = (clock_t)((double)clock() + seconds * CLOCKS_PER_SEC);
while (goal > clock());
}
#else
#include <time.h>
#define NSEC 1000000000
#define TYPE long
void do_foo(double sec) {
struct timespec start_time;
struct timespec current_time;
clock_gettime(CLOCK_REALTIME, &start_time);
while(1) {
clock_gettime(CLOCK_REALTIME, ¤t_time);
TYPE cur_nsec=(long)((current_time.tv_sec-start_time.tv_sec-sec)*NSEC + current_time.tv_nsec - start_time.tv_nsec);
if(cur_nsec>=0)
break;
}
}
#endif