# Source code for spinn_utilities.timer

# Copyright (c) 2017-2018 The University of Manchester
#
# This program is free software: you can redistribute it and/or modify
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
import sys
import time
from datetime import timedelta
# pylint: disable=no-name-in-module

if sys.version_info >= (3, 7):
# acquire the most accurate measurement available (perf_counter_ns)
_now = time.perf_counter_ns  # pylint: disable=no-member
# conversion factor
_NANO_TO_MICRO = 1000.0

def _convert_to_timedelta(time_diff):
""" Have to convert to a timedelta for rest of code to read.

As perf_counter_ns is nano seconds, and time delta lowest is micro,
need to convert.
"""
return timedelta(microseconds=time_diff / _NANO_TO_MICRO)

else:
# acquire the most accurate measurement available (perf_counter)
_now = time.perf_counter  # pylint: disable=no-member

def _convert_to_timedelta(time_diff):
""" Have to convert to a timedelta for rest of code to read.

As perf_counter is fractional seconds, put into correct time delta.
"""
return timedelta(seconds=time_diff)

[docs]class Timer(object):
""" A timer used for performance measurements.

Recommended usage::

with Timer() as timer:
... do stuff that takes time ...

elapsed_time = timer.measured_interval

or alternatively::

timer = Timer()
timer.start_timing()
... do stuff that takes time ...
elapsed_time = timer.take_sample()

Mixing these two styles is *not recommended*.
"""

__slots__ = [

# The start time when the timer was set off
"_start_time",

# The time in the measured section
"_measured_section_interval"
]

def __init__(self):
self._start_time = None
self._measured_section_interval = None

[docs]    def start_timing(self):
""" Start the timing. Use :py:meth:take_sample to get the end.
"""
self._start_time = _now()

[docs]    def take_sample(self):
""" Describes how long has elapsed since the instance that the\
:py:meth:start_timing method was last called.

:rtype: datetime.timedelta
"""
time_now = _now()
diff = time_now - self._start_time
return _convert_to_timedelta(diff)

def __enter__(self):
self.start_timing()
return self

def __exit__(self, *_args):
self._measured_section_interval = self.take_sample()
return False

@property
def measured_interval(self):
""" Get how long elapsed during the measured section.

:rtype: datetime.timedelta
"""
return self._measured_section_interval