Time series logging

How do I use this?

Consider this example of a ‘simulation’ logging various quantities:

from time import sleep
from random import uniform
from pytools.log import (LogManager, add_general_quantities,
        add_simulation_quantities, add_run_info, IntervalTimer,
        LogQuantity, set_dt)

from warnings import warn

class Fifteen(LogQuantity):
    def __call__(self):
        return 15

def main():
    logmgr = LogManager("mylog.dat", "w")  # , comm=...

    # set a run property
    logmgr.set_constant("myconst", uniform(0, 1))


    vis_timer = IntervalTimer("t_vis", "Time spent visualizing")
    logmgr.add_watches(["step.max", "t_sim.max", "t_step.max"])

    for istep in range(200):

        dt = uniform(0.01, 0.1)
        set_dt(logmgr, dt)

        # Illustrate custom timers
        if istep % 10 == 0:
            with vis_timer.start_sub_timer():

        # Illustrate warnings capture
        if uniform(0, 1) < 0.05:
            warn("Oof. Something went awry.")



if __name__ == "__main__":

(You can find this example as examples/log.py in the pytools source distribution.)

Running this script will give you a file mylog.dat. Note how log quantities given as “watches” are also periodically logged to the console.

To analyze this data, we need some tools that are distributed as part of the ‘datapyle’ package on Github, which we need to install first:

$ pip install git+https://github.com/inducer/datapyle.git

To prepare this data set for analysis, run runalyzer-gather as a script:

$ runalyzer-gather summary.dat mylog.dat
Scanning...          [########################################] ETA ?
Importing...         [########################################] ETA ?

This step may look unnecessary here, but it serves two important functions:

  • If you would like to compare data from multiple runs, you can simply add data files from multiple runs and analyze them side-by-side.

  • For distributed-memory runs, you can likewise gve data sets from multiple ranks to be gathered in a single file for centralized analysis.

  • As well as, naturally, any combination of the above.

After this, you may use runalyzer (also in datapyle) to analyze the summary file:

# -m enables '$quantity' in SQL
$ runalyzer -m summary.dat
Runalyzer running on Python 3.8.5 (default, Aug  2 2020, 15:09:07)
[GCC 10.2.0]
Copyright (c) Andreas Kloeckner 2008
Run .help to see help for 'magic' commands

This is a normal Python console, but it has a few extra tricks up its sleeve. .help gives an overview. Here, we’ll focus on demonstrating two interesting features. First, lets get an overview of all the logged quantities:

>>> .quantities
id | name    | unit | description                 | rank_aggregator
7  | dt      | s    | Simulation Timestep         | None
9  | fifteen | None | None                        | None
5  | step    | 1    | Timesteps                   | None
2  | t_2step | s    | Step-to-step duration       | None
3  | t_cpu   | s    | Wall time                   | None
4  | t_log   | s    | Time spent updating the log | None
6  | t_sim   | s    | Simulation Time             | None
1  | t_step  | s    | Time step duration          | None
8  | t_vis   | s    | Time spent visualizing      | None

Next, we could plot, e.g. time step duration against simulation time:

>>> .plot select $t_sim, $t_2step

Next, a fact that the select may have given away: The argument to .plot is a SQL query that is passed on to sqlite3, with support for some additional syntax. You can see what this query expanded to internally:

>>> mangle_sql("select $t_sim, $t_2step")
'select t_sim.value, t_2step.value from runs  inner join t_sim on (t_sim.run_id = runs.id)  inner join t_2step on (t_2step.run_id = runs.id and t_sim.step = t_2step.step and t_sim.rank=t_2step.rank) '

As you can see, by default these queries return data from all runs. You can filter which runs you are interested in through run properties:

>>> .runprops

simply by adding a SQL where clause referring to these properties.

As you can see from the demo, you can of course add your own, application-focused run properties.

This means that you have the full power of SQL available to analyze your time series data, for example:

  • Plot the solution 2-norms of all runs that were run on a Tuesday between time step 2000 and 3000

  • Make a scatterplot correlating memory transfer amounts and simulation time

Log Quantity Abstract Interfaces

class pytools.log.LogQuantity(name, unit=None, description=None)[source]

A source of loggable scalars.

__init__(name, unit=None, description=None)[source]

Initialize self. See help(type(self)) for accurate signature.


Perform updates required at every LogManager tick.


Return the current value of the diagnostic represented by this LogQuantity or None if no value is available.

This is only called if the invocation interval calls for it.

class pytools.log.PostLogQuantity(name, unit=None, description=None)[source]

A source of loggable scalars.

__init__(name, unit=None, description=None)

Initialize self. See help(type(self)) for accurate signature.


Perform updates required at every LogManager tick.

class pytools.log.MultiLogQuantity(names, units=None, descriptions=None)[source]

A source of multiple loggable scalars.

class pytools.log.MultiPostLogQuantity(names, units=None, descriptions=None)[source]

Log Manager

class pytools.log.LogManager(filename=None, mode='r', mpi_comm=None, capture_warnings=True, commit_interval=90)[source]

A distributed-memory-capable diagnostic time-series logging facility. It is meant to log data from a computation, with certain log quantities available before a cycle, and certain other ones afterwards. A timeline of invocations looks as follows:




In a time-dependent simulation, each group of tick_before() tick_after() calls captures data for a single time state, namely that in which the data may have been before the “compute” step. However, some data (such as the length of the timestep taken in a time-adpative method) may only be available after the completion of the “compute…” stage, which is why tick_after() exists.

A LogManager logs any number of named time series of floats to a file. Non-time-series data, in the form of constants, is also supported and saved.

If MPI parallelism is used, the “head rank” below always refers to rank 0.

Command line tools called runalyzer (in the datapyle package) are available for looking at the data in a saved log.

__init__(filename=None, mode='r', mpi_comm=None, capture_warnings=True, commit_interval=90)[source]

Initialize this log manager instance.

  • filename – If given, the filename to which this log is bound. If this database exists, the current state is loaded from it.

  • mode – One of “w”, “r” for write, read. “w” assumes that the database is initially empty. May also be “wu” to indicate that a unique filename should be chosen automatically.

  • mpi_comm – A mpi4py.MPI.Comm. If given, logs are periodically synchronized to the head node, which then writes them out to disk.

  • capture_warnings – Tap the Python warnings facility and save warnings to the log file.

  • commit_interval – actually perform a commit only every N times a commit is requested.


Data retrieval

get_expr_dataset(expression, description=None, unit=None)[source]

Prepare a time-series dataset for a given expression.


expression – A pymbolic expression that may involve the time-series variables and the constants in this LogManager. If there is data from multiple ranks for a quantity occuring in this expression, an aggregator may have to be specified.


(description, unit, table), where table is a list of tuples (tick_nbr, value).

Aggregators are specified as follows: - qty.min, qty.max, qty.avg, qty.sum, qty.norm2 - qty[rank_nbr] - qty.loc


Return a joint data set for a list of expressions.


expressions – a list of either strings representing expressions directly, or triples (descr, unit, expr). In the former case, the description and the unit are found automatically, if possible. In the latter case, they are used as specified.


A triple (descriptions, units, table), where table is a a list of [(tstep, (val_expr1, val_expr2,...)...].



Add quantities that are printed after every time step.

set_constant(name, value)[source]

Make a named, constant value available in the log.

add_quantity(quantity, interval=1)[source]

Add an object derived from LogQuantity to this manager.

Time Loop


Record data points from each added LogQuantity that is not an instance of PostLogQuantity. Also, invoke PostLogQuantity.prepare_for_tick() on PostLogQuantity instances.


Record data points from each added LogQuantity that is an instance of PostLogQuantity.

May also checkpoint data to disk.


Add generic run metadata, such as command line, host, and time.

Built-in Log General-Purpose Quantities

class pytools.log.IntervalTimer(name, description=None)[source]

Records elapsed times supplied by the user either through sub-timers, or by explicitly calling add_time().

__init__(name, description=None)[source]

Initialize self. See help(type(self)) for accurate signature.

class pytools.log.LogUpdateDuration(mgr, name='t_log')[source]

Records how long the last log update in LogManager took.

__init__(mgr, name='t_log')[source]

Initialize self. See help(type(self)) for accurate signature.

class pytools.log.EventCounter(name='interval', description=None)[source]

Counts events signaled by add().

__init__(name='interval', description=None)[source]

Initialize self. See help(type(self)) for accurate signature.

class pytools.log.TimestepCounter(name='step')[source]

Counts the number of times LogManager ticks.

class pytools.log.StepToStepDuration(name='t_2step')[source]

Records the CPU time between invocations of LogManager.tick_before() and LogManager.tick_after().


Initialize self. See help(type(self)) for accurate signature.

class pytools.log.TimestepDuration(name='t_step')[source]

Records the CPU time between the starts of time steps. LogManager.tick_before() and LogManager.tick_after().


Initialize self. See help(type(self)) for accurate signature.

class pytools.log.CPUTime(name='t_cpu')[source]

Records (monotonically increasing) CPU time.


Initialize self. See help(type(self)) for accurate signature.

class pytools.log.ETA(total_steps, name='t_eta')[source]

Records an estimate of how long the computation will still take.

__init__(total_steps, name='t_eta')[source]

Initialize self. See help(type(self)) for accurate signature.


Add generally applicable LogQuantity objects to mgr.