natural | Natural sorting in Go

I'd like to confirm the battery usage of an app I am developing on iOS, specifically on Xcode 13 and iOS 15. (Note: This app previously showed no issues with battery usage on previous versions of iOS.)

Previously, it seems that there were two ways to gather energy usage information:

#1. On the device under Settings > Developer > Logging

• As per Apple's documentation described in the section titled "Log Energy Usage Directly on an iOS Device".
• However, on iOS15, I can't find any options for logging under Developer or anywhere under settings even when searching.

#2. Profiling via Instruments using the "Energy Log" template

• As per the same documentation from Apple described in the section "Use the Energy Diagnostics Profiling Template".
• While it is still available in Xcode 12, this template is missing in Xcode 13. Naturally, it's also not possible to profile an iOS15 device with Xcode 12.

Digging through the Xcode 13 release notes, I found the following:

Instruments no longer includes the Energy template; use metrics reporting in the Xcode Organizer instead. (74161279)

When I access the Organizer in Xcode (12 or 13), select an app and click "Energy" for all versions of the app, it shows the following:

Apple's documentation for "Analyzing the Performance of Your Shipping App" says:

"In some cases the pane shows “Insufficient usage data available,” because there may not be enough anonymized data reported by participating user devices. When this happens, try checking back in a few days."

Well over a year into production and having sufficient install numbers, I have a feeling that waiting a few days might not do much.

I would like to determine if this is a bug in my app or a bug in iOS15. How can energy usage data be gathered using Xcode 13 on iOS 15?

I am trying to encode a small lambda calculus with algebraic datatypes in Scheme. I want it to use lazy evaluation, for which I tried to use the primitives delay and force. However, this has a large negative impact on the performance of evaluation: the execution time on a small test case goes up by a factor of 20x.

While I did not expect laziness to speed up this particular test case, I did not expect a huge slowdown either. My question is thus: What is causing this huge overhead with lazy evaluation, and how can I avoid this problem while still getting lazy evaluation? I would already be happy to get within 2x the execution time of the strict version, but faster is of course always better.

Below are the strict and lazy versions of the test case I used. The test deals with natural numbers in unary notation: it constructs a sequence of 2^24 sucs followed by a zero and then destructs the result again. The lazy version was constructed from the strict version by adding delay and force in appropriate places, and adding let-bindings to avoid forcing an argument more than once. (I also tried a version where zero and suc were strict but other functions were lazy, but this was even slower than the fully lazy version so I omitted it here.)

I compiled both programs using compile-file in Chez Scheme 9.5 and executed the resulting .so files with petite --program. Execution time (user only) for the strict version was 0.578s, while the lazy version takes 11,891s, which is almost exactly 20x slower.

I have observed that GCC's C++ compiler generates the following assembler code:

We've had a working Ansible AWX instance running on v5.0.0 for over a year, and suddenly all jobs stop working -- no output is rendered. They will start "running" but hang indefinitely without printing out any logging.

The AWX instance is running in a docker compose container setup as defined here: https://github.com/ansible/awx/blob/5.0.0/INSTALL.md#docker-compose

Standard troubleshooting such as restarting of containers, host OS, etc. hasn't helped. No configuration changes in either environment.

Upon debugging an actual playbook command, we observe that the command to run a playbook from the UI is like the below:

ssh-agent sh -c ssh-add /tmp/awx_11021_0fmwm5uz/artifacts/11021/ssh_key_data && rm -f /tmp/awx_11021_0fmwm5uz/artifacts/11021/ssh_key_data && ansible-playbook -vvvvv -u ubuntu --become --ask-vault-pass -i /tmp/awx_11021_0fmwm5uz/tmppo7rcdqn -e @/tmp/awx_11021_0fmwm5uz/env/extravars playbook.yml

That's broken down into three commands in sequence:

1. ssh-agent sh -c ssh-add /tmp/awx_11021_0fmwm5uz/artifacts/11021/ssh_key_data
2. rm -f /tmp/awx_11021_0fmwm5uz/artifacts/11021/ssh_key_data
3. ansible-playbook -vvvvv -u ubuntu --become --ask-vault-pass -i /tmp/awx_11021_0fmwm5uz/tmppo7rcdqn -e @/tmp/awx_11021_0fmwm5uz/env/extravars playbook.yml

You can see in part 3, the -vvvvv is the debugging argument -- however, the hang is happening on command #1. Which has nothing to do with ansible or AWX specifically, but it's not going to get us much debugging info.

I tried doing an strace to see what is going on, but for reasons given below, it is pretty difficult to follow what it is actually hanging on. I can provide this output if it might help.

So one natural question with command #1 -- what is 'ssh_key_data'?

Well it's what we set up to be the Machine credential in AWX (an SSH key) -- it hasn't changed in a while and it works just fine when used in a direct SSH command. It's also apparently being set up by AWX as a file pipe:

prw------- 1 root root 0 Dec 10 08:29 ssh_key_data

Which starts to explain why it could be potentially hanging (if nothing is being read in from the other side of the pipe).

Running a normal ansible-playbook from command line (and supplying the SSH key in a more normal way) works just fine, so we can still deploy, but only via CLI right now -- it's just AWX that is broken.

So the question then becomes "why now"? And "how to debug"? I have checked the health of awx_postgres, and verified that indeed the Machine credential is present in an expected format (in the main_credential table). I have also verified that can use ssh-agent on the awx_task container without the use of that pipe keyfile. So it really seems to be this piped file that is the problem -- but I haven't been able to glean from any logs where the other side of the pipe (sender) is supposed to be or why they aren't sending the data.

I'm using godbolt to get assembly of the following program:

I am trying to find a more efficient solution to a combinatorics problem than the solution I have already found.

Suppose I have a set of N objects (indexed 0..N-1) and wish to consider each subset of size K (0<=K<=N). There are S=C(N,K) (i.e., "N choose K") such subsets. I wish to map (or "encode") each such subset to a unique integer in the range 0..S-1.

Using N=7 (i.e., indexes are 0..6) and K=4 (S=35) as an example, the following mapping is the goal:
0 1 2 3 --> 0
0 1 2 4 --> 1
...
2 4 5 6 --> 33
3 4 5 6 --> 34

N and K were chosen small for the purposes of illustration. However, in my actual application, C(N,K) is far too large to obtain these mappings from a lookup table. They must be computed on-the-fly.

In the code that follows, combinations_table is a pre-computed two-dimensional array for fast lookup of C(N,K) values.

All code given is compliant with the C++14 standard.

If the objects in a subset are ordered by increasing order of their indexes, the following code will compute that subset's encoding:

Consider a program with the following two translation units:

I have 4 files all in the same directory: main.rakumod, infix_ops.rakumod, prefix_ops.rakumod and script.raku:

• main module has a class definition (class A)
• *_ops modules have some operator routine definitions to write, e.g., $a1 + $a2 in an overloaded way.
• script.raku tries to instantaniate A object(s) and use those user-defined operators.

Why 3 files not 1? Since class definition might be long and separating overloaded operator definitions in files seemed like a good idea for writing tidier code (easier to manage).

e.g.,

I have a parent SCS View(SingleChildScrollView) and a child SCS View. Inside the child SCS View there is a Data Table, and the Data Table starts at around bottom quarter of the screen.

Now, I want to scroll the parent SCS View when the user scrolls to the top of Data Table inside child SCS View.

This works naturally in web, but does not work in iOS or anroid. I tried using same Scrollcontroller for both parent & child SCS View and played around with ScrollPhysics. But nothing seem to work. Can you please help me with a solution.

Here is the code: