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Measure code execution with precision using Python’s time.perf_counter_ns.

# Python time.perf_counter_ns Usage

In Python, the `time.perf_counter_ns` function is used to measure the elapsed time in nanoseconds. This function is part of the `time` module in Python and provides a high-resolution timer for measuring the performance of code execution.

## Understanding `time.perf_counter_ns`

The `time.perf_counter_ns` function returns the current value of a performance counter, specifically in nanoseconds. This value is useful for measuring the duration of code execution with high precision. It is important to note that the value returned by `time.perf_counter_ns` is platform-dependent and can vary based on the system’s hardware and implementation.

### Example Usage

Here is an example demonstrating the usage of `time.perf_counter_ns` in Python:

“`python
import time

start_time = time.perf_counter_ns()

# Code block to measure the performance of

end_time = time.perf_counter_ns()

elapsed_time_ns = end_time – start_time
print(f”Elapsed time: {elapsed_time_ns} nanoseconds”)
“`

In this example, `start_time` is assigned the current value of the performance counter before the code block execution, and `end_time` is assigned the value after the code block execution. By calculating the difference between these two values, we can determine the elapsed time in nanoseconds.

## Distinction Between CPU Time and Wall Time

When measuring the time taken for a task, it is common to differentiate between CPU time and wall time.

– **CPU Time**: CPU time refers to the total time spent by the processor executing a task. It can be calculated using `time.process_time()` which returns the processor time for the current process.

– **Wall Time**: Wall time, on the other hand, represents the actual elapsed time from the start to the end of a task. It can be obtained using `time.perf_counter()` or `time.time()` functions which return the difference between two time points.

It’s essential to understand the distinction between CPU time and wall time when analyzing the performance of code execution.

## Conclusion

In conclusion, `time.perf_counter_ns` in Python is a valuable tool for accurately measuring the elapsed time in nanoseconds during code execution. By utilizing this function along with an understanding of CPU time and wall time, developers can evaluate the performance of their code and optimize it for efficiency. Remember to consider platform differences when working with high-resolution timer functions like `time.perf_counter_ns`.