Counting Sudoku Solution Grids using Monte Carlo

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How many ways can you fill a 9x9 grid, obeying all the rules of the sudoku puzzle? The answer is too big to just calculate directly on a computer, so an exact answer takes careful analysis. But if an absolutely exact answer isn’t required, we can get a good statistical approximation using a Monte Carlo algorithm. As a bonus, the algorithm doesn’t need any application-specific analysis and works on many other problems, too. It’s a handy “stupid things that work” approach to solving problems.

Terraform is Best for Configuring Hashicorp Vault

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Hashicorp Vault is a handy tool for scalable secrets management in a distributed system or team-based project. Unfortunately, the only out-of-the-box way to configure it is through its API (or a UI), but most projects that need Vault will need to manage the configuration in source control.

There’s a workaround explained on the Hashicorp blog. It’s a neat hack, but here’s a quick note about why using Terraform’s Vault integration is a better idea for production use.

Compression, Complexity and Software System Design

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Information theory gives us a way to understand communication systems, by giving us a way to understand what happens to information as it’s transmitted or re-encoded.

We can also study what happens to complexity in a software system as components depend on or interface each other. Just like we can make rigorous arguments about how much information can be compressed, we can make arguments about how much complexity can be simplified, and use this to make better choices when designing software systems.

What is the D Runtime, Anyway?

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D’s runtime is a recurring hot topic, but there’s obviously a lot of confusion about what the D runtime even is. I gave a quick explanation during my talk at DConf 2017, but I decided to write a blog post because I’ve seen confusion since then, and because I think blog posts are just a much better format for technical stuff, anyway.

If You Need Lifeboats, That Means Your Ship is Sinking

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It’s 1912 and Captain Edward Smith is boarding the RMS Titanic. He sees the lifeboats on deck and shakes his head with a heavy sigh before turning to the crew. “In my experience, I’ve never needed lifeboats. They’re not best practices — if you need lifeboats, that means your ship is sinking!” The crew members are enlightened and eagerly throw all lifeboats overboard. The Titanic begins its voyage to New York.

Update

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Just a quick update because I’ve been too busy to write much recently.

I’m giving a talk at DConf 2017 in Berlin! D’s been growing strongly in the past five years, and DConf’s been growing dramatically since the first one in 2013, so it’s pretty exciting to get involved. No, really. I often give tech talks at no-name events here in Sydney, but I’m half scared I’ll wet my pants on stage with a lineup like this — in my university days, I used to read all the C++ books by Andrei Alexandrescu and Scott Meyer that I could get my hands on.

If you have a DConf ticket, I look foward to seeing you there. If not, then you can look forward to watching the videos :)

Instead of writing a real blog post, I’m dropping a link to this classic about backwards compatibility nightmares, which you might like if you thought the mess that’s x86 BIOS booting was interesting. It’s a chapter from The Old New Thing, a book by Raymond Chen from Microsoft, based on his blog. Raymond Chen has spent a lot of his career making sure new versions of Windows can still run old software, no matter how badly the old software abused APIs and deserved to crash. Most of the technical details belong to the 90s, but there are plenty of morals for software development in the real world today. If you can read that chapter without ever wanting to weep for the industry, you’re stronger than I am.

D for Bare Metal Programming

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Previously I talked about booting a PC directly to bare metal D and said that Hello World is never a strong test of a programming environment. To get a better feel for what D is really like on bare metal, I wrote Xanthe, a simple, classic-style vertical scrolling shooter game with no dependencies on either the D or C runtime.

Friends Don't Let Friends Use PyCrypto

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For all practical purposes, PyCrypto, the Python Cryptography Toolkit, is dead. The package has several issues (many of them with security implications) that will almost certainly never get fixed because the project hasn’t been updated in multiple years. Despite that, I still see PyCrypto recommendations around every now and then — I just got it removed from the Awesome Cryptography list.

BIOS Boot to D

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After my previous post on using D for C-like programming, I wondered about going deeper. What’s the minimum it would take to run C-like D code on a PC? Could it run straight from a BIOS bootloader?

If you seriously want to make an OS, you’re much better off using an existing bootloader like U-Boot or GRUB, or at least using UEFI. But doing it this way is interesting because the x86 PC has an insane level of backwards compatibility, and booting from the BIOS to a modern high-level language is like doing an archealogical dig through the past 40 years of computing history.

Completely Ripping the Runtime out of D

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Most high level languages are built as a layer on top of C. That includes out-of-the-box D, but it doesn’t have to be that way: D is a plausible candidate for a “better C”. I think this is a pretty cool idea, so I’ve been experimenting with it to see what’s possible. The dmd compiler (and very soon the ldc2 compiler) has a -betterC command line flag that’s intended to remove dependencies on the D runtime. Unfortunately, it’s still extremely rudimentary — the docs only promise it “omit[s] generating some runtime information and helper functions” — so in practice it’s hard to write non-trivial D code without getting runtime dependencies, even if you don’t need them in theory.

With a little linker hacking, it’s possible to rip these unnecessary dependencies out of compiled D code. As an example, I’ll completely remove all references to the D runtime out of some compiled D code so that it can link directly to some C, as if it were C code to begin with.