Enzo 2.2 documentation

Performance Measurement

EnzoTiming.h and performance_tools

This framework consists of two pieces – one that is part of enzo, primarily contained in src/enzo/EnzoTiming.h, and another which is used to plot and analyze the performance data, in src/performance_tools/performance_tools.py.

Usage Overview

We have added support for simple, lightweight measurements for the timing and performance of Enzo. This allows one to examine which functions are using the majority of the simulation runtime, and how this varies across multiple processors. We have built in a number of default timers, such as EvolveLevel for each level, RebuildHierarchy, SolveHydroEquations, and Group_WriteAllData. Below, we will outline how to add additional timers and how to generate plots of the data.

File Format

At each cycle, information is printed out to a file named performance.out. It collects the amount of time taken on each of the processors to complete the listed functions (e.g. Level N EvolveLevel, RebuildHiearchy, etc.) over that cycle. Rather than giving all of the values returned by each processor for a given function, EnzoTiming only outputs the mean amount of time spent per processor, the maximum & minimum amount of time across processors, and the standard deviation of this distribution of times. This is meant to give the user a sense of how well load-balanced their simulation is across processors, as well as pinpoint where the majority of the time is being spent. To explain the output, we show an example cycle from performance.out:

Cycle_Number 2
Level_0 6.520748e-05 8.344650e-07 6.389618e-05 6.604195e-05 100 4 3.833916e+05
Level_1 3.254414e-05 2.804866e-05 1.406670e-05 8.106232e-05 10 1 7.681875e+04
Level_2 1.159906e-04 2.678922e-05 9.965897e-05 1.623631e-04 14 1 3.017485e+04
Level_3 2.477765e-04 7.348677e-05 2.028942e-04 3.750324e-04 16 1 1.614358e+04
Level_4 5.816817e-04 1.630557e-04 4.820824e-04 8.640289e-04 24 1 1.031492e+04
Level_5 1.266718e-03 3.594168e-04 1.056910e-03 1.889229e-03 26 1 5.131371e+03
Level_6 2.686501e-03 7.197988e-04 2.262831e-03 3.933191e-03 40 1 3.722315e+03
RebuildHierarchy 5.715549e-03 1.371242e-04 5.478144e-03 5.801201e-03
SolveHydroEquations 1.436710e-03 2.407243e-03 4.386902e-05 5.606174e-03
Total 1.499003e-02 3.440975e-05 1.494408e-02 1.503992e-02 230 10 3.835882e+03
Each of the Level_N and Total lines have:
Level_N, mean time, stddev time, min time, max time, number of cell updates,
number of grids, mean cell updates/s/processor
Each non-level line (RebuildHierarchy, SolveHydroEquations, etc.) have:
Section Name, mean time, stddev time, min time, max time.

Time is measured in seconds of wall time for each of the processors.

In the example above, we see that more time is being spent in RebuildHierarchy than in SolveHydroEquations, and that the load balance is quite poor for the SolveHydroEquations where the mean is 1.4 ms, with a standard deviation of 2.4 ms.

At the beginning of each simulation (on Cycle 1), we print out a header to the performance.out file:

# This file contains timing information
# For instructions on how to decipher this information,
# see [enzo base directory]/src/performance_tools/README.
# Times are collected across MPI processes and presented as:
# Level_N/Total, mean time, std_dev time, min time, max time, cell updates, grids, cell updates/processor/sec
# Routine, mean time, std_dev time, min time, max time

Then, at the start of each simulation (whether the beginning or a restart), we print out the MPI processor count:

# Starting performance log. MPI processes: 4

This is done in case the number of processors changes over time.

Adding New Timers

While there are a number of default timers, it is easy to add new timers to any section of code in Enzo.

The built-in timers include: EvolveHierarchy (Total), EvolveLevel (for each level), SolveHydroEquations, RebuildHierarchy, and Group_WriteAllData. Adding new times should be as simple as doing two things:

  1. Add
#include "EnzoTiming.h"

to the top of the file you want to profile, making sure it is before macros_and_parameters.

  1. Add



around the code you want to time.

The string that you pass in gets collected in a map which is then iterated over at the end of each evolve hierarchy. At that time it prints into a file named performance.out.

Note: To make sure all processors register a timer, be sure to place the start/stop calls in a location that all processors will reach. If this is not possible, you must first register the timer with TIMER_REGISTER(“YourTimerName”).

Generating Plots

performance_tools.py (located in src/performance_tools) is a python module for plotting the performance information stored in performance.out. The easiest way to generate plots from performance.out is to call performance_tools.py from the command line:

python performance_tools.py performance.out
python performance_tools.py -s 11 performance.out

to do the same while applying a smoothing kernel to your data 11 cycles in width.

By default, performance_tools.py will output 8 plots:

Plot the mean time taken per processor on each level and on the simulation as a whole (Total) versus cycle number. Overplot in lighter tones are the minimum and maximum time taken on a processor for each of these quantities.
Same as p1.png except scale everything to be as a fraction of the total time taken.
Plot the mean time taken per processor on each level versus cycle number. Stack each level on the previous layer cumulatively.
Plot the mean time taken per processor performing any Non-Level fields versus cycle number (e.g. the RebuildHiearchy, SolveHydroEquations, and Group_WriteAllData tasks). Stack each level on the previous layer cumulatively. Scale everything to be as a fraction of the total time taken.
Plot the number of cells updated at each level versus cycle number and stack them cumulatively.
Plot the efficiency (cell updates/processor/sec) for each level and for the simulation as a whole versus cycle number.
Plot the load balancing (Max Time - Min Time) for all subprocesses and levels of the simulation as a whole versus time.
Plot the load balancing (Max Time - Min Time) for all subprocesses and levels of the simulation as a whole versus time. Normalize them by the mean time taken for each process.

Generating Additional Plots

If you want to create additional plots of your data beyond the defaults, simply add new plot_quantities() and plot_stack() calls to the bottom of performance_tools.py.

This can be as simple as adding one of these lines:

# Plot the mean time taken per processor on Level 0 EvolveLevel calls versus
# Cycle Number.
p.plot_quantity("Level 0", "Mean Time")

# Same as above, but stacks the quantity from zero to the mean time.
p.plot_stack("Level 0", "Mean Time")

# Plot the mean time take per processor for all defined fields (All levels,
# All Functions)
p.plot_quantity([], "Mean Time", repeated_field="All")

# Plot and stack cumulatively on top of each other the number of cell
# updates for each level versus cycle number.
p.plot_stack([], "Cell Updates", repeated_field="Level")

# Plot the mean time taken per processor for all non-level functions versus
# cycle number (including "Total" time taken by everything).
p.plot_quantity("Total", "Mean Time", repeated_field="Non-Level")

Full documentation for the plot_quantity and plot_stack functions can be found in the docstrings for the performance_tools.py module. You can view it either by looking at the source code, or by loading it in python:

import performance_tools as pt
Samuel Skillman (samskillman at gmail.com)
Cameron Hummels (chummels at gmail.com)