Julia v1.9 Release Notes

New language features

It is now possible to assign to bindings in another module using setproperty!(::Module, ::Symbol, x). ([#44137])
Slurping in assignments is now also allowed in non-final position. This is handled via Base.split_rest. ([#42902])

Language changes

New builtins getglobal(::Module, ::Symbol[, order]) and setglobal!(::Module, ::Symbol, x[, order]) for reading from and writing to globals. getglobal should now be preferred for accessing globals over getfield. ([#44137])

Compiler/Runtime improvements

Command-line option changes

In Linux and Windows, --threads=auto now tries to infer usable number of CPUs from the process affinity which is set typically in HPC and cloud environments ([#42340]).
--math-mode=fast is now a no-op ([#41638]). Users are encouraged to use the @fastmath macro instead, which has more well-defined semantics.
The --threads command-line option now accepts auto|N[,auto|M] where M specifies the number of interactive threads to create (auto currently means 1) ([#42302]).

Multi-threading changes

Threads.@spawn now accepts an optional first argument: :default or :interactive. An interactive task desires low latency and implicitly agrees to be short duration or to yield frequently. Interactive tasks will run on interactive threads, if any are specified when Julia is started ([#42302]).

Build system changes

New library functions

Iterators.flatmap was added ([#44792]).
New helper Splat(f) which acts like x -> f(x...), with pretty printing for inspecting which function f was originally wrapped. ([#42717])

Library changes

A known concurrency issue of iterate methods on Dict and other derived objects such as keys(::Dict), values(::Dict), and Set is fixed. These methods of iterate can now be called on a dictionary or set shared by arbitrary tasks provided that there are no tasks mutating the dictionary or set ([#44534]).
Predicate function negation !f now returns a composed function (!) ∘ f instead of an anonymous function ([#44752]).
RoundFromZero now works for non-BigFloat types ([#41246]).
Dict can be now shrunk manually by sizehint! ([#45004]).
@time now separates out % time spent recompiling invalidated methods ([#45015]).
@time_imports now shows any compilation and recompilation time percentages per import ([#45064]).

Standard library changes

Package Manager

LinearAlgebra

The methods a / b and b \ a with a a scalar and b a vector, which were equivalent to a * pinv(b), have been removed due to the risk of confusion with elementwise division ([#44358]).
We are now wholly reliant on libblastrampoline (LBT) for calling BLAS and LAPACK. OpenBLAS is shipped by default, but building the system image with other BLAS/LAPACK libraries is not supported. Instead, it is recommended that the LBT mechanism be used for swapping BLAS/LAPACK with vendor provided ones. ([#44360])
normalize(x, p=2) now supports any normed vector space x, including scalars ([#44925]).

Markdown

Printf

Random

randn and randexp now work for any AbstractFloat type defining rand ([#44714]).

REPL

SparseArrays

Dates

Downloads

Statistics

Sockets

Tar

Distributed

The package environment (active project, LOAD_PATH, DEPOT_PATH) are now propagated when adding local workers (e.g. with addprocs(N::Int) or through the --procs=N command line flag) ([#43270]).
addprocs for local workers now accept the env keyword argument for passing environment variables to the workers processes. This was already supported for remote workers ([#43270]).

UUIDs

Unicode

graphemes(s, m:n) returns a substring of the m-th to n-th graphemes in s ([#44266]).

Mmap

DelimitedFiles

Deprecated or removed

Unexported splat is deprecated in favor of exported Splat, which has pretty printing of the wrapped function. ([#42717])

External dependencies

Tooling Improvements