PrintThis section is provided for interest only - as it only applies to ArcGIS Desktop - not Pro (which is natively 64 bit). It is recommended that you only read/skim through the section and check out the computation time comparison at the end without performing the described steps yourself and then loop back to it at the end of the lesson if you have free time and are interested in exploring 64-bit Background Geoprocessing in ArcGIS Desktop.
A number of versions ago (since Server 10.1), Esri added support for 64-bit arcpy. Esri also introduced 64-bit geoprocessing using the 64-bit Background Geoprocessing patch which was part of 10.1 Service Pack 1 as an option in ArcGIS Desktop (Pro is entirely 64-bit) to work around these memory issues for large geoprocessing tasks. Not all tools support 64-bit geoprocessing within Desktop and there are some tricks to getting it installed so you can access it in Desktop. There is also a 64-bit arcpy geoprocessing library so you can run your code (any code) from the command line. Background Geoprocessing (64-bit) is still available as a separate installation on top of ArcGIS (see this ArcMap/Background Geoprocessing (64-bit) page) and we’ve provided a link for students to obtain it within Canvas. You'll find this link on the "64-bit Geoprocessing downloads for ArcGIS (optional)" page under Lesson 1 in Canvas.
As Esri hint in their documentation, 64-bit processing within ArcGIS Desktop requires that the tool run in the background. This is because it is running using a separate set of tools which are detached from the Desktop application (which is 32-bit). Personally, I rarely use Background Geoprocessing but I do make use of the 64-bit version of Python that it installs to run a lot of my scripts in 64-bit mode from the command line.
If you’ve typically run your code in the past from within an IDE (such as PythonWin, IDLE or spyder) or from within ArcGIS you might not be aware that you can also run that code from the command line by calling Python directly.
For ArcGIS Desktop you can start a regular command prompt and, using the standard Windows commands, change to that path where your Python script is located. Usually when you open a command window, it will start in your home folder (e.g. c:\users\yourname). We could dedicate an entire class to operating system commands but Microsoft has a good resource at this Windows Commands page for those who are interested.
We just need a couple of the commands listed there :
- cd : change directory. We use this to move around our folders. Full help at this Commands/cd page.
- dir : list the files and folders in my directory. Full help at this Commands/dir page.
We’ll change the directory to where our code from section 1.6 is (e.g. mine is c:\wcgis\geog489\lesson1) and see how to run the script using the command line versions of 32-bit and 64-bit Python.
cd c:\wcgis\geog489\lesson1
If you downloaded and installed the 64-bit Background Geoprocessing from above you will have both 32-bit and 64-bit Python installed. We’ll use the 32-bit Python first which should be located at c:\python27\arcgis10.6\python.exe (substitute 10.6 by whichever version of ArcGIS you have installed).
There’s a neat little feature built into the command line where you can use the TAB key to autocomplete paths so you could start typing c:\python27\a and then hit TAB and you should see the path cycling through the various ArcGIS folders.
We’ll run our code using:
C:\python27\ArcGIS10.6\python.exe myScriptName.py
Where myScriptName.py is whatever you saved the code from section 1.6 as. You will now see the code run in the command window and pop up all of the same messages you would have seen if you had run it from an IDE (but not the AddMessages messages as they are only interpreted by ArcGIS).
To run the code against the 64-bit version of Python the command is almost identical except that you’ll use the x64 version of Python that has been installed by Background Geoprocessing. In my case that means the command is:
C:\python27\ArcGISx6410.5\python.exe myScriptName.py
Once your script finishes you’ll have a few time stamp values. Running that code from Section 1.6 through the 32-bit and 64-bit versions a few times we have some sample results below. The first runs of each are understandably slower as arcpy is imported for the first time. You have probably witnessed this behavior yourself as your code takes longer the very first time it runs.
| 32-bit Desktop | 64-bit Desktop | 64-bit Pro |
|---|---|---|
| 149 seconds | 107 seconds | 109 seconds |
| 119 seconds | 73 seconds | 144 seconds |
| 91 seconds | 90 seconds | 111 seconds |
| 85 seconds | 73 seconds | |
| 93 seconds | 75 seconds |
We can see a couple of things with these results – they are a little inconsistent depending on what else my PC was doing at the time the code was running and, if you are looking at individual executions of the code, it is difficult to see which pieces of the code are slower or faster from time to time. This is the problem that we will solve later in the lesson when we look at profiling code where we examine how long each line of code takes to run.