Felipe O. Carvalho
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felipe.rs
Felipe O. Carvalho
@felipe.rs
1.4K followers 480 following 940 posts
SWE @ dbt Labs. Past: SDF, VoDa, Spotify. Apache Arrow/Databases/Compilers/DistSys. Rust/C++/OCaml/TLA+. 🇧🇷 → 🇸🇪 → 🌎 http://bento.me/felipe / https://felipe.rs
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felipe.rs
You can post about semaphores, atomics, and syscalls on LinkedIn if you want.
Weekend Rust excursion: implementing a semaphore that is as clean as the C++20 implementation. You can implement a semaphore using a Mutex and a Condvar, but these are heavy-weight constructs. A semaphore is a very simple primitive and doesn't need all the functionality provided by these. All we need is the equivalent of std::atomic<uint32_t>::wait() and std::atomic<uint32_t>::notify_all() available in C++20. The equivalent doesn't exist in stable Rust yet. atomic-wait is a very minimal crate that provides a portable façade to the futex() syscall (Linux), WaitOnAddress/WakeByAddressAll (Windows), and __libcpp_atomic_wait/__cxx_atomic_notify_all (for other platforms). Just include that crate, and then you can implement a very clean semaphore by combining atomic_wait::wait()/wake_all() with the standard Rust Atomic32.
November 13, 2025 at 2:02 PM
felipe.rs
If we forbid the inlining, the caller is forced to put i on the stack

str r0, [sp, #4]

to pass the ptr to add10

add r0, sp, #4 // put the ptr relative to the stack ptr on r0 before call

then the value is loaded from the stack into r1 before the printf call

ldr r1, [sp, #4]
__attribute__((noinline)) int add10(int *num) { return *num += 10; }
November 8, 2025 at 7:48 PM
felipe.rs
add10(int *) versus add10 inlined. When you take a "pointer" from a local variable and "pass" it to a function, but the compiler knows the pointer is not a pointer but the register that contains the local variable.
#include <cstdio> int add10(int *num) { return *num += 10; } int external_int(); int main(int argc, char *argv[]) { int i = external_int(); add10(&i); printf("%d", i); return 0; }
November 8, 2025 at 7:48 PM
felipe.rs
It’s only a 20-ish% increase from June in Brazil, so I’m securing mine before they have to renew their inventory and increase it even more.
380 BRL for Kingston Furybeast 16GB in June (~70 USD)
November 8, 2025 at 3:57 AM
felipe.rs
“wE lAunChed our SaaS a mONth ago and alReady mADE it to 1M ARR”
Friendly reminder that multiplying revenue by 12 is not ARR
October 26, 2025 at 1:31 PM
felipe.rs
To be fixed in C++ 2026.
September 15, 2025 at 11:40 PM
felipe.rs
I installed Termios on my iPhone and I can SSH to my MacBook (Tailscale FTW), run tmux, Neovim and Amp (AI coding agent CLI) from anywhere. 😌
September 15, 2025 at 11:38 PM
felipe.rs
Very observant of Sam to notice the consequences of AI on the internet.
Sam Altman: i never took the dead internet theory that seriously but it seems like there are really a lot of LLM-run twitter accounts now
September 8, 2025 at 5:00 PM
felipe.rs
Puns in Gothenburg 🇸🇪
June 19, 2025 at 10:24 AM
felipe.rs
New book ✨
Practical Foundations for Programming Languages 2nd edition. Robert Harper
February 6, 2025 at 4:55 PM
felipe.rs
They removed optionals when transitioning to proto2 to proto3 and then people demanded their optionals back. Optionals came back, but implement in a much worse manner. Putting it under an experimental flag didn't deter people from using it elsewhere though.
This file contains proto3 optional fields, but --experimental_allow_proto3_optional was not set.\n" }
January 27, 2025 at 9:58 PM
felipe.rs
I think I’ve achieved the right level of @fly.io networking understanding.
December 23, 2024 at 3:55 PM
felipe.rs
I remember when it was nVIDIA and not Nvidia or NVIDIA.
December 23, 2024 at 1:20 PM
felipe.rs
I'm parsing JSON that contains numbers with two decimal places and I want to store them as Decimals on the database. Python offers a way to avoid the limitations of the floating point representation of the number strings that appear in the JSON text! This will work even when numbers are not in "".
parse_float is an optional function that will be called with the string of every JSON float to be decoded. By default, this is equivalent to float(num_str). This can be used to use another datatype or parser for JSON floats (e.g. decimal.Decimal).
December 18, 2024 at 2:46 PM
felipe.rs
Needy Duolingo owl asking me to extend my daily streak.
December 14, 2024 at 8:35 PM
felipe.rs
I guess that kinda makes protobuf unsuitable for the representation of ASTs.
[DISCUSS] Workaround Protobuf deserialization depth limit in Substrait We have accidentally encountered a deserialization limit of official protobuf library with a deep nesting. The limit is 100 (https://protobuf.dev/programming-guides/proto-limits/#depth), that is, the library will fail to parse a message if it contains more than 100 nestings. So I would like to discuss extending Substrait to reference fragment of scalar expression as it already does for the RelOp tree.
December 9, 2024 at 7:37 PM
felipe.rs
🤿|🤿🤿🤿+

Made it more interesting ;)
December 7, 2024 at 12:52 PM
felipe.rs
httpcats.com/500.jpg
December 7, 2024 at 12:43 PM
felipe.rs
I wrote a SQL query. #sql #datascience #bolhadev
WITH time_series AS ( SELECT "returns".date, rf.rate rf_rate, rf.log1p rf_log1p, "returns".log_return, FROM "returns" ASOF JOIN rolling_rf_rate rf ON "returns".date >= rf.date ORDER BY "returns".date ), rolling AS ( SELECT date, -- annualized risk-free rate rf_rate, rf_log1p, -- daily returns and excess returns log_return, log_return - (rf_log1p / $trading_days_per_year) AS excess_log_return, EXP(log_return) - 1 AS simple_return, EXP(excess_log_return) - 1 AS excess_simple_return, -- window offset and dimension first_value(date) OVER rolling_window AS window_start_date, COUNT(*) OVER rolling_window AS window_trading_days, -- annualized values based on log returns (SUM(log_return) OVER rolling_window * $trading_days_per_year) / window_trading_days AS rolling_annual_log_return, rolling_annual_log_return - rf_log1p AS rolling_annual_excess_log_return, (STDDEV_POP(excess_log_return) OVER rolling_window) * SQRT($trading_days_per_year) AS rolling_annual_log_stddev, -- rolling volatility as a simple ratio EXP(rolling_annual_log_stddev) - 1 AS rolling_annual_volatility, -- sharpe ratio rolling_annual_excess_log_return / rolling_annual_log_stddev AS rolling_sharpe_ratio, FROM time_series WINDOW rolling_window AS ( ORDER BY date RANGE BETWEEN $window_m1 PRECEDING AND CURRENT ROW ) ) SELECT * FROM rolling WHERE -- exclude the first window that may not have enough data date >= (SELECT MIN(date) FROM rolling) + $window_m1
December 7, 2024 at 12:35 PM
felipe.rs
Yet another case of “hardware companies should be creating compilers and new programming models instead of just hardware.”

NVIDIA is a hardware and compiler company.
Lisa Su (AMD): I think our strategy is that we have to increase performance continually. For gaming in particular, the gaming software developers have not necessarily used all the cores from time to time. There is no physical reason we couldn't go past 16 cores. The key is that we're going at a pace that the software guys can and do utilise it.
December 6, 2024 at 12:24 PM
felipe.rs
Updated version with zip().
if len(dates) == 0: yield (start_date, end_date) return if start_date < dates[0]: yield (start_date, dates[0] - timedelta(days=1)) for d0, d1 in zip(dates[:-1], dates[1:]): d0p1 = d0 + timedelta(days=1) if d0p1 < d1: yield (d0p1, d1 - timedelta(days=1)) if end_date > dates[-1]: yield (dates[-1] + timedelta(days=1), end_date)
December 3, 2024 at 1:08 PM
felipe.rs
Just implemented this function. A nightmare of off-by-one errors. Do you have a more elegant way of implementing it?
def generate_holes(dates: list, start_date: datetime.date, end_date: datetime.date): """ Generate holes in a sorted list of dates. Parameters ---------- dates : list Sorted list of dates. start_date : datetime.date Start date (inclusive). end_date : datetime.date End date (inclusive). Yields ------ tuple A tuple with the start and end dates of a hole. """ if len(dates) == 0: yield (start_date, end_date) return expected = start_date i = 0 while True: while expected == dates[i]: expected += timedelta(days=1) i += 1 if i >= len(dates): break if i >= len(dates): break hole_last = dates[i] - timedelta(days=1) yield (expected, hole_last) i += 1 if i >= len(dates): break expected = dates[i] if dates[-1] < end_date: yield (dates[-1] + timedelta(days=1), end_date)
December 3, 2024 at 1:44 AM
felipe.rs
Built-in iOS Calculator app is finally decent!
December 1, 2024 at 9:06 PM
felipe.rs
“creators” losing engagement after the changes made to Threads’ algorithm
Post that triggers lots of replies being replicated by multiple users farming for engagement: “Quero saber quem foi o cabeçudo que me inventou um caderno de 96 folhas, 96? Pq 96 e não 100?” Translation: “I want to know who was the big head who invented a 96-page notebook, 96? Why 96 and not 100?”
November 22, 2024 at 3:15 AM
felipe.rs
Arrow 18 (released by the end of October) is the last release to have so many commits (1 commit = 1 PR) from me.
arrow.apache.org/blog/2024/10...
65 Sutou Kouhei 41 Raúl Cumplido 35 Antoine Pitrou 21 Vibhatha Lakmal Abeykoon 19 Dane Pitkin 16 Felipe Oliveira Carvalho 16 Jonathan Keane 16 Joris Van den Bossche 16 Rossi Sun 16 mwish 13 Joel Lubinitsky 9 Laurent Goujon 7 Lysandros Nikolaou 7 Neal Richardson 6 Bryce Mecum 6 David Li 5 Matt Topol
November 22, 2024 at 12:06 AM