I created the following app_config.xml file (to restrict CPU multi-threading since I run multiple projects on a 4-core CPU) and placed it in my Cosmology@Home project directory:

<app_config>
    <app>
        <name>camb_boinc2docker</name>
        <max_concurrent>1</max_concurrent>
    </app>
    <app_version>
        <app_name>camb_boinc2docker</app_name>
        <plan_class>vbox64_mt</plan_class>
        <avg_ncpus>1</avg_ncpus>
        <max_ncpus>1</max_ncpus>
    </app_version>
</app_config>

However, upon restarting BOINC I receive the following [Event Log] error when this project initializes: Missing <app_config> in app_config.xml.

What's my problem?

How did you make the app_config.xml file? I suppose in Notepad?
Did you save it in ANSI encoding format, as opposed to Unicode or UTF-8?

<max_ncpus>1</max_ncpus> isn't an option in application configuration app_config.xml. Instead, it's an option in anonymous platform app_info.xml.

<app_config>
    <app>
        <name>camb_boinc2docker</name>
        <max_concurrent>1</max_concurrent>
    </app>
    <app_version>
        <app_name>camb_boinc2docker</app_name>
        <plan_class>vbox64_mt</plan_class>
        <avg_ncpus>1</avg_ncpus>
    </app_version>
</app_config>

---

Nice catch, Jord/Ageless! Thank-you. Re-saving the file in ANSI format corrected the original error. As I would expect now, though (until the new application download becomes available on Dec 3), I'm receiving the following error upon project initialization:

"Your app_config.xml file refers to an unknown application 'camb_boinc2docker'. Known applications: 'camb'"

Regarding your configuration file/option requirement reference, I'll see what happens after I accept at least one new job (and Docker container) prior to restarting my BOINC client, for which the specified configuration should be implemented on subsequent jobs. It would seem according to that referenced BOINC documentation, that the <avg_ncpus>x</avg_ncpus> option in app_config.xml provides the same intended limitation as does the <max_ncpus>x</max_ncpus> option in app_info.xml. I suppose regardless, though, if indeed <max_ncpus>x</max_ncpus> isn't [yet] an option in application configuration, app_config.xml, but rather only in anonymous platform, app_info.xml, then a change to the FAQ needs to be made immediately.

For <max_ncpus>, I mistakenly put it back in the example app_config.xml file I posted in my original post. I'd taken it out, but then copied your contents with the indentations, and forgot to take it out again. Sorry for that confusion, I have edited my post to take it out.

It would seem according to that referenced BOINC documentation, that the <avg_ncpus>x</avg_ncpus> option in app_config.xml provides the same intended limitation as does the <max_ncpus>x</max_ncpus> option in app_info.xml. I suppose regardless, though, if indeed <max_ncpus>x</max_ncpus> isn't [yet] an option in application configuration, app_config.xml, but rather only in anonymous platform, app_info.xml, then a change to the FAQ needs to be made immediately.

Which FAQ are you talking about?
If the entry about the app_config.xml file in the User Manual wikipedia page, <max_ncpus> isn't referenced there and doesn't need to as it isn't used there.

---

Thanks for the update and clarification. I'll be ready to use an app_info.xml file if my current app_config.xml fails to implement the project execution configuration that I desire.

The FAQ [item] I'm referring to is the one for this project: How can I limit the number of CPUs used?

Hello,
do you have a key "Enter" after last line?

Hello,
other thing is name of project,
for camb_legacy
it must be:

<app_config>
<app>
<name>camb</name>
<max_concurrent>2</max_concurrent>
</app>
</app_config>


and a key Enter after last line.
Directory is in data warehouse, for example
\data\projects\www.cosmologyathome.org\app_config.xml

Thanks Cwill_CZ, but my problem was fixed by saving my app_config.xml file in ANSI format (and using only the <avg_ncpus>1</avg_ncpus> option without the <max_ncpus>1</max_ncpus> option which is not available to app_config.xml).

And, I only need this file specifically for use with the camb_boinc2docker application as a means of restricting multiple/concurrent CPU core usage per job/task/WU within the VirtualBox environment as described in the current project FAQ. This "CPU behavior" is not an issue with the camb_legacy application (and is a completely different issue from that addressed by the <max_concurrent>X</max_concurrent> configuration option that you have included in your sample file).