hotspot
rand
hotspot | rand | |
---|---|---|
16 | 29 | |
3,874 | 1,577 | |
1.4% | 1.1% | |
9.3 | 8.3 | |
3 days ago | 3 days ago | |
C++ | Rust | |
GNU General Public License v3.0 or later | GNU General Public License v3.0 or later |
Stars - the number of stars that a project has on GitHub. Growth - month over month growth in stars.
Activity is a relative number indicating how actively a project is being developed. Recent commits have higher weight than older ones.
For example, an activity of 9.0 indicates that a project is amongst the top 10% of the most actively developed projects that we are tracking.
hotspot
- Hotspot: A GUI for the Linux perf profiler
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What is your favourite profiling tool for C++?
perf with Hotspot 👌
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Profiling C code on an M1 mac
If you’re able to use perf on Linux, I would recommend hotspot for visualizing the results.
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What is the problem with transfer speeds withing Dolphin?
I can recommend you using the https://github.com/KDAB/hotspot/ tool whenever you want to study performance.
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Data-driven performance optimization with Rust and Miri
Every Linux C/C++/Rust developer should know about https://github.com/KDAB/hotspot. It's convenient and fast. I use it for Rust all the time, and it provides all of these features on the back of regular old `perf`.
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How to interpret a flamegraph?
Flamegraphs alone aren't a full picture of what your application is doing, but it can give you hints as to where to look. Another tool I often use is Hotspot which can open the perf.data file and provide more options for filtering and digging into the gathered data beyond the single flamegraph.
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Twenty Years of Valgrind
Ignore the command, it's just a placeholder to get meaningful values. The -d flag adds basic cache events, by adding another -d you also get load and load miss events for the dTLB, iTLB and L1i cache.
But as mentioned, you can instrument any event supported by your system. Including very obscure events such as uops_executed.cycles_ge_2_uops_exec (Cycles where at least 2 uops were executed per-thread) or frontend_retired.latency_ge_2_bubbles_ge_2 (Retired instructions that are fetched after an interval where the front-end had at least 2 bubble-slots for a period of 2 cycles which was not interrupted by a back-end stall).
You can also record data using perf-record(1) and inspect them using perf-report(1) or - my personal favorite - the Hotspot tool (https://github.com/KDAB/hotspot).
Sorry for hijacking the discussion a little, but I think perf is an awesome little tool and not as widely known as it should be. IMO, when using it as a profiler (perf-record), it is vastly superior to any language-specific built-in profiler. Unfortunately some languages (such as Python or Haskell) are not a good fit for profiling using perf instrumentation as their stack frame model does not quite map to the C model.
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Linux Perf Examples
> [...] how Perf compares to vendor tools like vTune [...] ?
Regarding the hardware events that Perf can capture on x86, it has pretty much all of them. So it should be equivalent to vTune for all practical purposes.
The big difference is in the UI -- or absence thereof. Perf is a low-level tool and its output is mostly text files. There is a curses-based TUI for perf-report (and even gtk version, but it is essentially the same as the TUI, just using GTK2 widgets), but that's about it.
By contrast, vTune comes with a heavy (electron-based?) GUI and is quite helpful in guiding beginners, with many graphs and explanations.
Of course, one can (and is expected to) complement Perf with an assortment of tools that process its output for visualization. For example, the flamegraph [1] and heat map [2] tools described in the article. But also KDAB hotspot [3] or HPerf for a vTune-style perf-report.
[1] https://github.com/brendangregg/FlameGraph
[2] https://github.com/brendangregg/HeatMap
[3] https://github.com/KDAB/hotspot
[4] https://www.poirrier.ca/hperf/
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Parsers that don't yet exist?
https://github.com/KDAB/hotspot might contain parsing code you could use as an example (other than perf script). It always accepts raw perf.data, and there doesn't seem to be a way to feed it the output of perf script, so it might be parsing it directly instead of calling perf script.
rand
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We have getrandom at home
Making compatibility promises for distributions means they cannot take advantage of potential advancements in the field.
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Blog Post: On Random Numbers
Defining an error type that is meaningful, portable, and compatible with no-std isn't straightforward. If the std lib's getrandom requires std, then just like that, rand and many other crates won't use it anyway. Using io::Result seems to me to face this challenge.
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Hey Rustaceans! Got a question? Ask here (52/2022)!
Some wasm targets can’t generate random numbers at all but in the case of the book because you are using wasm in a browser you can use JS to generate random numbers. I believe there’s a way to get the rand crate to use JS as the backend for generating rand but its a bit more convoluted than the easy one-liner that the book suggests.
- Data-driven performance optimization with Rust and Miri
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What crates are considered as de-facto standard?
rand
- Why Rust?
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[Media] Nebulabrot rendered with Rust — Explanations in the comments
This uses rand and xcomplex to handle the mathematics, png to write image files, and dialoguer and indicatif for some pretty prompts and progress bars.
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Do you ever use unsafe { .. } when not implementing custom data structures or interacting with external C code?
You can often achieve this without any unsafe by putting an assert!() on the length before the hot loop. For example, I got rid of some unsafe in rand that way.
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Original source of `(seed * 9301 and 49297) % 233280` random algorithm?
This is a widely used method to map random integers to floating point numbers, but it has the disadvantage of wasting 1 bit of float mantissa precision.
On modern CPUs, its computational advantage over full-precision mapping methods, such as multiplication by a float, is not always clear [1].
[1] https://github.com/rust-random/rand/issues/416
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Any plans for built-in support of Vec2/Vec3/Vec4 in Rust?
In fact, there are a lot of crates in Rust where in other programming languages, it would be included in the standard library. Examples are regex, random number generators, additional iterator methods, macros for other collections, num traits, loggers, HTTP libraries, error handling, async runtimes, serialization and deserialization, date and time, and many more.
What are some alternatives?
FlameGraph - Stack trace visualizer
fastrand - A simple and fast random number generator
polkit-dumb-agent - a polkit agent in 145 lines of code, because polkit is dumb and none of the other agents worked
fast-float-rust - Super-fast float parser in Rust (now part of Rust core)
firestorm - A fast intrusive flamegraph
winapi-rs - Rust bindings to Windows API
gta5view - Open Source Snapmatic and Savegame viewer/editor for GTA V
yew - Rust / Wasm framework for creating reliable and efficient web applications
cargo-flamegraph - Easy flamegraphs for Rust projects and everything else, without Perl or pipes <3
cargo-fuzz - Command line helpers for fuzzing
optick-rs - Optick for Rust
rust - Rust for the xtensa architecture. Built in targets for the ESP32 and ESP8266