# \#ttfx

**URL:** https://discourse.julialang.org/tag/ttfx/943.md

[Latest](https://discourse.julialang.org/latest.md) · [Categories](https://discourse.julialang.org/categories.md) · [Tags](https://discourse.julialang.org/tags.md)

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## [Compiled application startup time under 10ms for 368MB sysimage](https://discourse.julialang.org/t/compiled-application-startup-time-under-10ms-for-368mb-sysimage/139313)

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**Author:** [@melevy](https://discourse.julialang.org/u/melevy)\
**Replies:** 0\
**Last updated:** [September 9, 2026, 3:14pm UTC](https://discourse.julialang.org/t/compiled-application-startup-time-under-10ms-for-368mb-sysimage/139313 "2026-09-09T15:14:08Z")

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I build compiled binaries for a network simulator and the process startup time really bugged me. Investigation showed that it is not really inherent to the problem. The image is mmapped fine, but then the loader walks tw…

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## [Load time of MTK models](https://discourse.julialang.org/t/load-time-of-mtk-models/138068)

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**Author:** [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Replies:** 4\
**Last updated:** [July 16, 2026, 5:09pm UTC](https://discourse.julialang.org/t/load-time-of-mtk-models/138068 "2026-07-16T17:09:02Z")

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I am not happy with the TTFX of our MTK models (see: RamAirKites.jl). We already cache our simplified model after building it and use a custom system image. But nevertheless, the time to load a model from our cache is st…

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## [Time to build system and problem is slower in Julia 1.12 with MTKv11](https://discourse.julialang.org/t/time-to-build-system-and-problem-is-slower-in-julia-1-12-with-mtkv11/135536)

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**Author:** [@Wen-Wei\_Tseng](https://discourse.julialang.org/u/Wen-Wei_Tseng)\
**Replies:** 12\
**Last updated:** [April 17, 2026, 3:23pm UTC](https://discourse.julialang.org/t/time-to-build-system-and-problem-is-slower-in-julia-1-12-with-mtkv11/135536 "2026-04-17T15:23:38Z")

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Hi, while I was trying the new version (v11) of ModelingToolkit.jl , I noticed it took longer to build the ODE system and problem under Julia 1.12. Here is the GitHub actions workflow running the script using ModelingT…

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## [Reactant.jl + Enzyme: ~10 min compilation overhead triggered by hidden-to-hidden Dense layers](https://discourse.julialang.org/t/reactant-jl-enzyme-10-min-compilation-overhead-triggered-by-hidden-to-hidden-dense-layers/136374)

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**Author:** [@Yuan-Ru-Lin](https://discourse.julialang.org/u/Yuan-Ru-Lin)\
**Replies:** 1\
**Last updated:** [March 27, 2026, 11:22am UTC](https://discourse.julialang.org/t/reactant-jl-enzyme-10-min-compilation-overhead-triggered-by-hidden-to-hidden-dense-layers/136374 "2026-03-27T11:22:11Z")

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I’ve been investigating compilation times with Reactant.jl + Lux + AutoEnzyme() on an NVIDIA GPU and found a reproducible jump in TTFT (Time-To-First-Training) when a model includes hidden-to-hidden Dense layers. Minima…

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## [New Julia versions, higher Pluto loading times](https://discourse.julialang.org/t/new-julia-versions-higher-pluto-loading-times/135187)

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**Author:** [@VivMendes](https://discourse.julialang.org/u/VivMendes)\
**Replies:** 38\
**Last updated:** [February 4, 2026, 12:24am UTC](https://discourse.julialang.org/t/new-julia-versions-higher-pluto-loading-times/135187 "2026-02-04T00:24:27Z")

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I will start teaching two courses (one undergraduate with 350 students and the other a master’s course with 40 students) at the beginning of February. None of those courses involves CS students, which implies that the co…

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## [\[ANN\] PrecompileSignatures.jl: Generate precompile directives by reading method signatures](https://discourse.julialang.org/t/ann-precompilesignatures-jl-generate-precompile-directives-by-reading-method-signatures/80943)

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**Author:** [@rikh](https://discourse.julialang.org/u/rikh)\
**Replies:** 14\
**Last updated:** [January 1, 2026, 12:43pm UTC](https://discourse.julialang.org/t/ann-precompilesignatures-jl-generate-precompile-directives-by-reading-method-signatures/80943 "2026-01-01T12:43:23Z")

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PrecompileSignatures.jl is a package which reduces TTFX by moving some just in time compilation to the precompilation phase. The package does this by reading all method signatures in a package and generating precompile d…

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## [A visual log of loading and precompilation times for many packages over a variety of julia versions](https://discourse.julialang.org/t/a-visual-log-of-loading-and-precompilation-times-for-many-packages-over-a-variety-of-julia-versions/133887)

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**Author:** [@Krastanov](https://discourse.julialang.org/u/Krastanov)\
**Replies:** 10\
**Last updated:** [November 22, 2025, 7:06pm UTC](https://discourse.julialang.org/t/a-visual-log-of-loading-and-precompilation-times-for-many-packages-over-a-variety-of-julia-versions/133887 "2025-11-22T19:06:08Z")

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At Julia Ecosystem Benchmarks Explorer you can find detailed benchmarks of loading time for many packages over many different versions of julia, all interactively explorable. This is the culmination of: @tecosaur sett…

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## [Startup time of 1000 packages – 53% slower in Julia 1.12 vs 1.10](https://discourse.julialang.org/t/startup-time-of-1000-packages-53-slower-in-julia-1-12-vs-1-10/128343)

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**Author:** [@fonsp](https://discourse.julialang.org/u/fonsp)\
**Replies:** 81\
**Last updated:** [November 14, 2025, 7:28pm UTC](https://discourse.julialang.org/t/startup-time-of-1000-packages-53-slower-in-julia-1-12-vs-1-10/128343 "2025-11-14T19:28:21Z")

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Startup time of 1000 packages I think startup time is a big deal for Julia, especially for new users. If it takes a long time to load a package, it makes Julia look bad. Recently, Julia 1.12 beta was released, and I not…

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## [Mystery of invalidations in V\>1.10. Even in precompiled code](https://discourse.julialang.org/t/mystery-of-invalidations-in-v-1-10-even-in-precompiled-code/132081)

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**Author:** [@joa-quim](https://discourse.julialang.org/u/joa-quim)\
**Replies:** 10\
**Last updated:** [September 7, 2025, 3:42pm UTC](https://discourse.julialang.org/t/mystery-of-invalidations-in-v-1-10-even-in-precompiled-code/132081 "2025-09-07T15:42:15Z")

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I have reported before the very large degradation in TTFP in GMT for version 1.11 and later. One example as reminder | | |\_| | | | (\_| | | Version 1.10.10 (2025-06-27) \_/ |\\\_\_'\_|\_|\_|\\\_\_'\_| | Official https://juli…

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## [TTFX for Julia 1.11 much faster than with Julia 1.10](https://discourse.julialang.org/t/ttfx-for-julia-1-11-much-faster-than-with-julia-1-10/130022)

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**Author:** [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Replies:** 1\
**Last updated:** [June 19, 2025, 12:57pm UTC](https://discourse.julialang.org/t/ttfx-for-julia-1-11-much-faster-than-with-julia-1-10/130022 "2025-06-19T12:57:04Z")

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We see that the initialization of an MTK problem, using Julia 1.11 is much faster than with Julia 1.10. For details, see: System initialization on Julia 1.10 is slow · Issue #233 · ufechner7/KiteModels.jl · GitHub Julia…

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## [Slower times to TTFX for GMT in 1.11 and even more in nightly](https://discourse.julialang.org/t/slower-times-to-ttfx-for-gmt-in-1-11-and-even-more-in-nightly/126350)

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**Author:** [@joa-quim](https://discourse.julialang.org/u/joa-quim)\
**Replies:** 6\
**Last updated:** [March 25, 2025, 7:08pm UTC](https://discourse.julialang.org/t/slower-times-to-ttfx-for-gmt-in-1-11-and-even-more-in-nightly/126350 "2025-03-25T19:08:39Z")

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Hi, I’ve been delaying this post but not that time to v1.12 release seems to approach I think I should not delay it no more. Since the 1.10 I have notice that building and using has become progressively slower but this…

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## [Compilation latency with constant propagation and unreachable branches](https://discourse.julialang.org/t/compilation-latency-with-constant-propagation-and-unreachable-branches/114667)

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**Author:** [@jishnub](https://discourse.julialang.org/u/jishnub)\
**Replies:** 7\
**Last updated:** [May 24, 2024, 2:44pm UTC](https://discourse.julialang.org/t/compilation-latency-with-constant-propagation-and-unreachable-branches/114667 "2024-05-24T14:44:46Z")

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With julia\> function f(a, b) if a == 1 return b \* b elseif a == 2 return b \* b' elseif a == 3 return b' \* b else re…

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## [Investigating large latency on a constrained Windows environment](https://discourse.julialang.org/t/investigating-large-latency-on-a-constrained-windows-environment/114482)

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**Author:** [@TimG](https://discourse.julialang.org/u/TimG)\
**Replies:** 85\
**Last updated:** [May 22, 2024, 2:21pm UTC](https://discourse.julialang.org/t/investigating-large-latency-on-a-constrained-windows-environment/114482 "2024-05-22T14:21:14Z")

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On first start-up in the morning in VSCode, my code takes fully 7 minutes before executing the first line of my actual script (to read a csv file). using DataFrames using CSV using Dates using ZipArchives using GeoStats…

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## [Why does Pkg.activate(".") require compilation? Time to first project activation](https://discourse.julialang.org/t/why-does-pkg-activate-require-compilation-time-to-first-project-activation/101193)

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**Author:** [@mkitti](https://discourse.julialang.org/u/mkitti)\
**Replies:** 2\
**Last updated:** [July 5, 2023, 3:00am UTC](https://discourse.julialang.org/t/why-does-pkg-activate-require-compilation-time-to-first-project-activation/101193 "2023-07-05T03:00:18Z")

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Pkg.activate(".") seems to to take about 200 milliseconds, mostly due to compilation. It still takes 40 milliseconds even after activating the same environment again. $ julia -e 'using Pkg; for i in 1:5; @time Pkg.activ…

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## [This month in Julia world - 2023-05](https://discourse.julialang.org/t/this-month-in-julia-world-2023-05/99634)

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**Author:** [@Krastanov](https://discourse.julialang.org/u/Krastanov)\
**Replies:** 20\
**Last updated:** [June 9, 2023, 10:04pm UTC](https://discourse.julialang.org/t/this-month-in-julia-world-2023-05/99634 "2023-06-09T22:04:04Z")

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There was a call to action for someone to make a newsletter that lists interesting developments in the Julia world, in order to communicate improvements to the language that are not visible unless you track Github and Sl…

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## [Any way to speed up loading large precompiled packages?](https://discourse.julialang.org/t/any-way-to-speed-up-loading-large-precompiled-packages/98762)

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**Author:** [@moble](https://discourse.julialang.org/u/moble)\
**Replies:** 35\
**Last updated:** [May 15, 2023, 12:54pm UTC](https://discourse.julialang.org/t/any-way-to-speed-up-loading-large-precompiled-packages/98762 "2023-05-15T12:54:05Z")

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I have a package that my collaborators want to use like a script. Specifically, they want it to load quickly. Once it’s compiled, my part of the code is fast — around 0.01s, compared to the several seconds taken by my …

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## [\[ANN\] SnoopPrecompile -\> PrecompileTools](https://discourse.julialang.org/t/ann-snoopprecompile-precompiletools/97882)

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**Author:** [@tim.holy](https://discourse.julialang.org/u/tim.holy)\
**Replies:** 22\
**Last updated:** [May 4, 2023, 4:26pm UTC](https://discourse.julialang.org/t/ann-snoopprecompile-precompiletools/97882 "2023-05-04T16:26:09Z")

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SnoopPrecompile is being deprecated in favor of PrecompileTools. If you maintain a General-registry package that uses SnoopPrecompile, you should soon receive a pull request that will migrate you to PrecompileTools. Othe…

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## [Package load speed: Windows vs Linux](https://discourse.julialang.org/t/package-load-speed-windows-vs-linux/93039)

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**Author:** [@tfiers](https://discourse.julialang.org/u/tfiers)\
**Replies:** 24\
**Last updated:** [March 28, 2023, 12:21pm UTC](https://discourse.julialang.org/t/package-load-speed-windows-vs-linux/93039 "2023-03-28T12:21:21Z")

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I have a feeling that Julia package import times are significantly faster on Linux than on Windows. See e.g. this thread where: @giordano’s seven-year-old Linux laptop loads Unitful in 0.44 seconds my two-year-old Win…

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## [First Pluto notebook launches are slower on Julia 1.9 beta 3](https://discourse.julialang.org/t/first-pluto-notebook-launches-are-slower-on-julia-1-9-beta-3/93429)

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**Author:** [@fonsp](https://discourse.julialang.org/u/fonsp)\
**Replies:** 157\
**Last updated:** [February 10, 2023, 3:30pm UTC](https://discourse.julialang.org/t/first-pluto-notebook-launches-are-slower-on-julia-1-9-beta-3/93429 "2023-02-10T15:30:58Z")

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Hi! :waving\_hand: Today, I ran some benchmarks to compare real-life launch times for first-time users of Julia 1.9.0-beta3 vs Julia 1.8.5. That means people who just installed Julia on their computer, and they are excite…

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## [Much worse import time for \`Statistics\` and \`SparseArrays\` on julia 1.9.0 nightly?](https://discourse.julialang.org/t/much-worse-import-time-for-statistics-and-sparsearrays-on-julia-1-9-0-nightly/83679)

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**Author:** [@Krastanov](https://discourse.julialang.org/u/Krastanov)\
**Replies:** 3\
**Last updated:** [January 12, 2023, 12:43am UTC](https://discourse.julialang.org/t/much-worse-import-time-for-statistics-and-sparsearrays-on-julia-1-9-0-nightly/83679 "2023-01-12T00:43:30Z")

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I am confused by this. Why would Statistics (or its dependency SparseArrays), a package in the standard library, have such a bad time to import? Anything I can do about this in my package that depends on Statistics? I ha…

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## [Julia for Scientists: summary slides](https://discourse.julialang.org/t/julia-for-scientists-summary-slides/91397)

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**Author:** [@tfiers](https://discourse.julialang.org/u/tfiers)\
**Replies:** 40\
**Last updated:** [December 26, 2022, 1:44pm UTC](https://discourse.julialang.org/t/julia-for-scientists-summary-slides/91397 "2022-12-26T13:44:09Z")

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I gave a presentation on Julia today, for staff of my uni’s Psychology department. Many interested people in the audience! These are the slides: (It starts slow but quickly goes into more nerdy terrain; The audience…

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## [ANN: New package SnoopPrecompile](https://discourse.julialang.org/t/ann-new-package-snoopprecompile/84778)

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**Author:** [@tim.holy](https://discourse.julialang.org/u/tim.holy)\
**Replies:** 32\
**Last updated:** [September 30, 2022, 3:10pm UTC](https://discourse.julialang.org/t/ann-new-package-snoopprecompile/84778 "2022-09-30T15:10:21Z")

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EDIT: SnoopPrecompile has been replaced by PrecompileTools. I’m pleased to announce the availability of SnoopPrecompile, a new package that can help reduce latency particularly on Julia 1.8 and higher. The concept of th…

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## [Juliad and julias, wrappers to DaemonMode and -J sysimage for quicker Linux/Cygwin scripts](https://discourse.julialang.org/t/juliad-and-julias-wrappers-to-daemonmode-and-j-sysimage-for-quicker-linux-cygwin-scripts/76690)

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**Author:** [@jdad](https://discourse.julialang.org/u/jdad)\
**Replies:** 3\
**Last updated:** [August 8, 2022, 11:00am UTC](https://discourse.julialang.org/t/juliad-and-julias-wrappers-to-daemonmode-and-j-sysimage-for-quicker-linux-cygwin-scripts/76690 "2022-08-08T11:00:55Z")

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FWIW, as an old linuxer, I have created for my own usage two scripts to facilitate the use of either sysimage or DaermonMode.jl to get faster frequently used scripts (=faster TTFX, Time to First X). Sorry, I have done th…

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## [\[ANN\] DLMReader 0.4.5 with one Big Enhancement](https://discourse.julialang.org/t/ann-dlmreader-0-4-5-with-one-big-enhancement/83729)

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**Author:** [@sl-solution](https://discourse.julialang.org/u/sl-solution)\
**Replies:** 3\
**Last updated:** [July 11, 2022, 8:43am UTC](https://discourse.julialang.org/t/ann-dlmreader-0-4-5-with-one-big-enhancement/83729 "2022-07-11T08:43:22Z")

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I am excited to announce that DLMReader version 0.4.5 has been released. The new release includes several performance enhancements and bug fixes. For instance, reading multiple observations per line and type detecting ar…

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## [Interpreting \`JET\` warnings on a simple \`Polyester\` multithreaded loop](https://discourse.julialang.org/t/interpreting-jet-warnings-on-a-simple-polyester-multithreaded-loop/83681)

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**Author:** [@Krastanov](https://discourse.julialang.org/u/Krastanov)\
**Replies:** 7\
**Last updated:** [July 4, 2022, 3:12am UTC](https://discourse.julialang.org/t/interpreting-jet-warnings-on-a-simple-polyester-multithreaded-loop/83681 "2022-07-04T03:12:23Z")

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Polyester seems to be one of the bigger sources of TTFX in some of my libraries. It is similarly the main source of warnings when using JET. Below is a very simple multi-threaded loop that causes a large number of JET wa…

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## [Intermittent type inference calls during method evaluation](https://discourse.julialang.org/t/intermittent-type-inference-calls-during-method-evaluation/82241)

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**Author:** [@rikh](https://discourse.julialang.org/u/rikh)\
**Replies:** 2\
**Last updated:** [June 5, 2022, 10:41am UTC](https://discourse.julialang.org/t/intermittent-type-inference-calls-during-method-evaluation/82241 "2022-06-05T10:41:14Z")

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When looking through a first call for a longish method via StatProfilerHTML.jl, I see some type inference happening during the method body evaluation: (This is in Julia 1.8-rc1.) I think that this is caused by the m…

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## [Precompiling non-inferrable calls](https://discourse.julialang.org/t/precompiling-non-inferrable-calls/79771)

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**Author:** [@rikh](https://discourse.julialang.org/u/rikh)\
**Replies:** 2\
**Last updated:** [April 23, 2022, 4:54pm UTC](https://discourse.julialang.org/t/precompiling-non-inferrable-calls/79771 "2022-04-23T16:54:21Z")

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Let me start of by saying that precompile is great. It can move a lot of compilation time from the package loading to the precompilation stage. For people unfamiliar with precompile, when calling it on a function, it pr…

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## [Is \`keyword\_argument = Val{true}\` good practice or an antipattern?](https://discourse.julialang.org/t/is-keyword-argument-val-true-good-practice-or-an-antipattern/75543)

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**Author:** [@Krastanov](https://discourse.julialang.org/u/Krastanov)\
**Replies:** 19\
**Last updated:** [February 12, 2022, 7:31am UTC](https://discourse.julialang.org/t/is-keyword-argument-val-true-good-practice-or-an-antipattern/75543 "2022-02-12T07:31:41Z")

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I am seeing more and more library code that is written with keyword arguments of the form kwarg = Val{true} instead of kwarg = true or even kwarg::Bool = true. I know this is done in order to force specialization in prec…