crash – Macbook big sur not asking for password after closing lid

this past month i noticed my macbook pro does not lock the screen after closing the lid. this happened twice in the past month. after the first time it happened, i did a fresh install and reset smc and nvram.

the problem occurred again today and the logs are filled with google chrome and launchd stuff when the lid was supposedly closed. in the morning after around 7 hours, i woke up to it unlocked and right where i left off.

anyone else experience this before? what can i do? is this a security issue?

catalina – Big sur 11.2.2 very lagging on 2019 Macbook Pro

I have a late 2019 macbook pro (the base model). I’ve been running Catalina until yesterday when I upgraded to Big Sur 11.2.2. It’s noticeably laggy. Has anyone experienced this? I’m not sure if 11.2.1 was laggy, so I was considering downgrading. Does anyone know how I can downgrade to 11.2.1, and possibly back to Catalina?

big o notation – Recommend great books on Data Structures and Algorithms

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Summation and big theta

Can anyone suggest a starter book or website where I can find information and examples of putting functions under summation signs into Big Theta. basic Arihmetic , geometric, Quadratic are fine , but I would like to work on examples like
$$sum_{i = 1}^{log n} i cdot n text{ or } sum_{i = 1}^{log n} 10^i$$

Outdoor housing big enough for DSLR?

Can anybody recommend an outdoor camera housing big enough to hold a DSLR (or something like a Canon G1X)?

All the standard CCTV housings I can find have at most about 4″ of width inside – I need at least 5″.

Doesn’t need to be fancy – just something to keep out the snow and rain.

(reasonably priced would be nice)

internet – Easy file transfer for big files?

I need to transfer a big file (2.4 GB) to another person over internet. The recipient doesn’t want to (or can’t?) install any new software to the PC.

I googled what are the preferred methods nowadays for this purpose, and I was lead to two quite interesting sounding free open-source services:, and All three seem to work through mere browsers, not needing any accounts and the transfer seems to happen between the source and recipient directly, without e.g. first having to upload the file to some server (which has restrictions how big the file can be) from which the recipient downloads it etc.

However, I just don’t seem to get those three services to work. I am using the Firefox browser with them as suggested. doesn’t really go anywhere when I add the file, while and just seem to process the file seemingly forever, without giving any feedback if they are really doing anything or is the processing of the file progressing at all. I tried also with a bit smaller 400MB compressed file but didn’t have any better success. With a small file of 4MB of size, file and squidl did process it quickly.

Any idea if those aforementioned services should work (also with big files), how long does it normally take for them to process big files, and are there any alternatives that actually work?

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virtualization – If Linux is installed in a virtual environment on my mac can I open apps that big sur blocks?

I’m trying open this application: (It’s a research tool might might be great for my work so I really want to access it).

When I try and open the app I get the message: “You do not have permission to open the application “ECGWorkbench’. Contact your computer or network administrator for assistance.”

If I installed Linux in a virtual environment on my mac could I then open the the Linux version of the app?

big sur – Can I add a default setting as part of my Info.plist file for my Java application

Due to a bug in MacOS Big Sur I need to run the following comand

defaults write com.jthink.songkong "AppleWindowTabbingMode" manual

for my Java application with bundled version of java

Is there a way I can add this to my Info.plist file so it is already set automatically on new install, because difficult for each customer to run the command.

I managed to get it added during build time so my Info.plist file contains


but it has had no effect.

Im not clear if I have done something wrong or if it is just impossible.

How to express complexity of two functions considering it is the same in big O notation

I have two functions. a and b.

Both have linear complexity O(n).

fcn a (items)
    loop items -> item
fcn b (items)
    loop items -> item

    loop items -> item

    loop items -> item   

Though b obviously takes 3 times longer to run than a for the same input.

Is there any other notion / technical way to express the difference?

Or is it normal to say “it takes 3 times longer but still O(n) in time so w.e, let’s move on”