Computation Overview

Earth Engine is built on top of Google's tools and services for performing computations at a massive scale. To make it easy to run large geospatial analyses, the Earth Engine platform and API hide much of the complexity of the underlying parallel-processing infrastructure.

EECUs

Overview

Key Term: EECU - Earth Engine Compute Unit, an abstraction of computing power.

An Earth Engine Compute Unit (EECU) is a mechanism for representing an amount of instantaneous processing power. Earth Engine tracks the total computational footprint of tasks as a function of their EECU usage through time (EECU-seconds, EECU-hours, etc.). Because Google has many different types of processor cores, architectures, etc., EECUs are a useful abstraction for talking about computational power.

Motivation

EE users often want to make estimates about the amount of processing power required for their workflows, and EECUs provide a consistent metric for making comparisons.

Comparison with CPU metrics

Note: While EECU-seconds measure the amount of work that Earth Engine is performing, EECU-seconds don't correspond directly to CPU-seconds or wall clock seconds due to the fully managed nature of the service.

The number, type and architecture of machines working on a particular result can change over time. Because different physical cores can have different performance characteristics, Earth Engine abstracts all processing using EECUs. An EECU-hour (or any other unit of EECU-time) doesn't correspond to a wall clock time, so a job which consumes 10 EECU-hours may have an observed runtime of just a few minutes.

Stability and predictability

Sending the same (or similar) requests to Earth Engine can sometimes result in very different amounts of computation. Common drivers of differences include:

• caching, such as reusing the results of previous computations (including partial or intermediate results)
• different underlying data, such as varying numbers of satellite images, geometries of different complexity, etc.
• algorithm changes on the EE platform, including performance optimizations, bugfixes, etc.
• changes to client libraries, particularly if you depend on other users' EE code or packages

Benchmarks

Explore sample Earth Engine computation benchmarks.

Metrics for failed requests

Earth Engine doesn't provide performance metrics for failed requests/tasks, since these numbers would be inaccurate or misleading. As an example, if a job fails because a worker task became unresponsive, that worker's processing consumption wouldn't be able to factor into the total.

Profiler

The profiler provides information about EECU-time and memory usage (per algorithm and asset) resulting from the computation performed while it's enabled. Each row in the profiler output corresponds to an algorithm, computation, asset load or overhead operation as described in the 'Description' column. The columns in the profiler are:

Description

A textual description of the computation, algorithm, asset load or overhead operation being profiled.

Count

An indicator proportional to the number of times the operation described in 'Description' was invoked.

Compute

An indicator of EECU-time taken by the operation(s).

Current Mem

This column appears only if there was an error because the script

used too much memory. It shows the amount of memory in use on any single compute node at the moment the error occurred.

Peak Mem

Maximum memory used on any single compute node for the operation.

Enabling the profiler

Code Editor

Use the "Run with Profiler" button, as described in the Code Editor guide.

Python

Include the following code in your Python script to enable the profiler:

with ee.profilePrinting():
   print(ee.Number(3.14).add(0.00159).getInfo())

The profile will be printed when the context ends, whether or not any error occurred within the context.

To capture the profile as a string, write the profile to a string buffer:

import io

out = io.StringIO()
with ee.profilePrinting(destination=out) as p:
    print(ee.Number(3.14).add(0.00159).getInfo())

print('Output:')
print(out.getvalue())

Here is a suggestion for turning the profile string into a table for easier analysis in Colab and Jupyter Notebooks (note that this is just one approach and may not be suitable for all cases):

import re
import pandas as pd

lines = out.getvalue().split('\n')

column_names = re.split(r'\s{1,}', lines[0])
column_names = [name.strip() for name in column_names if name.strip()]

data = [
    [element for element in re.split(r'\s{2,}', line) if element.strip()]
    for line in lines[1:-1]
]

df = pd.DataFrame(data, columns=column_names)
display(df)