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"""
This configuration script shows an example of how to take checkpoints for
SimPoints using the gem5 stdlib. Simpoints are set via a Workload and the
gem5 SimPoint module will calculate where to take checkpoints based of the
SimPoints, SimPoints interval length, and the warmup instruction length.

This scipt builds a simple board with the gem5 stdlib with no cache and a
simple memory structure to take checkpoints. Some of the components, such as
cache hierarchy, can be changed when restoring checkpoints.

Usage
-----

```
scons build/X86/gem5.opt
./build/X86/gem5.opt \
    configs/example/gem5_library/checkpoints/simpoints-se-checkpoint.py

./build/X86/gem5.opt \
    configs/example/gem5_library/checkpoints/simpoints-se-restore.py
```
"""

import argparse

from gem5.simulate.exit_event import ExitEvent
from gem5.simulate.simulator import Simulator
from gem5.utils.requires import requires
from gem5.components.boards.simple_board import SimpleBoard
from gem5.components.memory.single_channel import SingleChannelDDR3_1600
from gem5.components.processors.simple_processor import SimpleProcessor
from gem5.components.processors.cpu_types import CPUTypes
from gem5.isas import ISA
from gem5.resources.workload import Workload
from pathlib import Path
from gem5.components.cachehierarchies.classic.no_cache import NoCache
from gem5.simulate.exit_event_generators import (
    save_checkpoint_generator,
)

requires(isa_required=ISA.X86)

parser = argparse.ArgumentParser(
    description="An example simpoint workload file path"
)

# The lone arguments is a file path to a directory to store the checkpoints.

parser.add_argument(
    "--checkpoint-path",
    type=str,
    required=False,
    default="se_checkpoint_folder/",
    help="The directory to store the checkpoint.",
)

args = parser.parse_args()

# When taking a checkpoint, the cache state is not saved, so the cache
# hierarchy can be changed completely when restoring from a checkpoint.
# By using NoCache() to take checkpoints, it can slightly improve the
# performance when running in atomic mode, and it will not put any restrictions
# on what people can do with the checkpoints.
cache_hierarchy = NoCache()

# Using simple memory to take checkpoints might slightly imporve the
# performance in atomic mode. The memory structure can be changed when
# restoring from a checkpoint, but the size of the memory must be maintained.
memory = SingleChannelDDR3_1600(size="2GB")

processor = SimpleProcessor(
    cpu_type=CPUTypes.ATOMIC,
    isa=ISA.X86,
    # SimPoints only works with one core
    num_cores=1,
)

board = SimpleBoard(
    clk_freq="3GHz",
    processor=processor,
    memory=memory,
    cache_hierarchy=cache_hierarchy,
)

board.set_workload(Workload("x86-print-this-15000-with-simpoints"))

dir = Path(args.checkpoint_path)
dir.mkdir(exist_ok=True)

simulator = Simulator(
    board=board,
    on_exit_event={
        # using the SimPoints event generator in the standard library to take
        # checkpoints
        ExitEvent.SIMPOINT_BEGIN: save_checkpoint_generator(dir)
    },
)

simulator.run()