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

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

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

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