The C++ Documentary Won't Show You a Number. I Will. - HFT University

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The C++ Documentary Won't Show You a Number. I Will.

Published: June 05, 2026

The C++ documentary dropped today, and it is a fine piece of filmmaking and a slightly dishonest piece of history. Not in what it says. In what it lets you assume.

Two and a half hours of the people who were actually in the room: Stroustrup, Stepanov, Sutter, Alexandrescu, a few Bell Labs survivors, somebody from CERN, somebody from a game studio, and about ninety seconds of Hudson River Trading talking about microseconds. The history is genuinely good, and I will give it that before I take anything away. But you come out of it believing two things that are not true, or at least not yet true, and both of them matter if you ship latency-sensitive C++ for a living.

You come away believing C++26 answered the memory-safety regulators. It did not. The headline fix, Profiles, did not ship. And the film asserts a performance-per-watt moat three separate times without ever putting a number on screen. Fine. I will put the number on screen. It is more interesting than the film's version anyway, because it inverts what you would guess.

What the film gets right

Give credit first. The structure the editors chose is the smartest thing in the documentary, and they never say it out loud: C++ has had two winters, not one, with a long boom between them. How it survived the first tells you almost everything about whether it survives the second.

The first winter was around 2000 to 2005. Dot-com crash, Java with a marketing budget C++ never had, executives saying Java would kill C++ in two years. Microsoft building C# so enterprise shops would stop writing every app twice. The film covers all of it. What the film also gets right, and what most people forget, is that none of that was the real threat. The real threat was that the hardware was still bailing everyone out. Clock frequency was still climbing, and as long as it climbed, "performance does not matter, just wait a year" was a defensible engineering position. If your bloated program is slow today, the faster part lands next quarter. In that world an efficient language is a tax nobody volunteers to pay.

Then the lunch counter closed. On May 7, 2004, Intel cancelled Tejas, the Pentium 4 successor that was supposed to run at frightening clock speeds, and its Xeon sibling Jayhawk along with it. The reason was heat. Early 90nm samples at 2.8 GHz were already pulling around 150 watts against roughly 84 for the comparable Prescott part, and the roadmap walked straight into a wall of watts. Intel pivoted to dual core. Single-thread clock plateaued in the 3 to 4 GHz band, and twenty years later that is still where we live. Herb Sutter wrote the obituary, "The Free Lunch Is Over", online in December 2004 and in Dr. Dobb's the following March. If you wanted your program faster after that, the hardware was done doing the work for you.

The winter we never had

Here is the part the film tells through the HRT segment, and the part the trading floor understands in its spine. The "wait a year for double the clock" bargain never applied to us.

When your product is tail latency, not throughput, a faster part next year does nothing for a hot path that is losing the race today. The thing you are optimizing is the time between a packet hitting the NIC and an order leaving it, and no vendor roadmap fixes that number for you. So while the rest of the industry spent the early 2000s deciding performance was solved, the people wiring exchange connectivity were already living in the post-free-lunch world. Our winter never came because our summer was never that warm. The film puts a figure on the modern version: HRT describes over a million lines of C++ across fifteen thousand files, around eighty-four thousand commits in 2025 alone, roughly eight hundred active contributors. That is not nostalgia for a language. That is a bet, renewed every morning, that you can have the abstraction and still own every cycle.

And the end of the free lunch is exactly what saved C++ the first time. Once frequency stopped scaling, the only way left to go faster was parallel, and parallel means you care which language gets the most out of the silicon. The film leans on the phrase performance per watt three times because it is the moat. C++11 landed almost a decade after the C++0x effort started, hauling in move semantics and, more importantly, an actual memory model, the Boehm and Adve work from PLDI 2008 that gave the C family its first formal account of threading. Andrei Alexandrescu had fired the public shot back in August 2004 with a Usenet post titled "Multithreaded programming: is the C++ standardization committee listening?", and for a while the answer was no. C++11 arrived right when the whole industry rediscovered that hardware is finite. That was the boom.

So far the documentary and I agree. Now we stop agreeing.

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