futhark

Added

• Warnings for overflowing literals, such as 1000 : u8.

• Futhark now supports an attribute system, whereby expressions can
  be tagged with attributes that provide hints or directions to the
  compiler. This is an expert-level feature, but it is sometimes
  useful.

Added

• Faster index calculations for very tight GPU kernels (such as the
  ones corresponding to 2D tiling).

• scan with vectorised operators (e.g. map2 (+)) is now faster
  in some cases.

• The C API has now been documented and stabilized, including
  obtaining profiling information (although this is still
  unstructured).

Fixed

• Fixed some cases of missing fusion (#953).

• Context deinitialisation is now more complete, and should not leak
  memory (or at least not nearly as much, if any). This makes it
  viable to repeatedly create and free Futhark contexts in the same
  process (although this can still be quite slow).

Added

• Binary operators now act as left-to-right sequence points with
  respect to size types.

• futhark bench now has more colourful and hopefully readable
  output.

• The compiler is now about 30% faster for most nontrivial programs.
  This is due to parallelising the inlining stage, and tweaking the
  default configuration of the Haskell RTS.

• futhark dataset is now about 8-10x faster.

Fixed

• Fixed some errors regarding constants (#941).

• Fixed a few missing type checker cases for sum types (#938).

• Fix OOB write in CUDA backend runtime code (#950).

Added

• reduce_by_index with f32-addition is now approximately 2x
  faster in the CUDA backend.

Fixed

• Fixed kernel extractor bug in if-interchange (#921).

• Fixed some cases of malformed kernel code generation (#922).

• Fixed rare memory corruption bug involving branches returning
  arrays (#923).

• Fixed spurious warning about entry points involving opaque return
  types, where the type annotations are put on a higher-order return
  type.

• Fixed incorrect size type checking for sum types in negative
  position with unknown constructors (#927).

• Fixed loop interchange for permuted sequential loops with more
  than one outer parallel loop (#928).

• Fixed a type checking bug for branches returning incomplete sum
  types (#931).

Added

• futhark pkg now shells out to curl for HTTP requests.

• futhark doc now supports proper GitHub-flavored Markdown, as it
  uses the cmark-gfm library internally.

• Top-level constants are now executed only once per program
  instance. This matters when Futhark is used to generate library
  code.

• futhark autotune is better at handling degrees of parallelism
  that assume multiple magnitudes during a single run.

• futhark pkg now uses curl to retrieve packages.

• Type errors are now printed in red for better legibility (thanks
  to @mxxo!).

Fixed

• Fixed incorrect handling of opaques in entry point return types.

• futhark pkg now works properly with GitLab (#899).

Added

• scan now supports operators whose operands are arrays. They are
  significantly slower than primitive-typed scans, so avoid them if
  at all possible.

• Precomputed constants are now handled much more efficiently.

• Certain large programs that rely heavily on inlining now compile
  orders of magnitude faster.

Fixed

• Some fixes to complicated module expressions.

• futhark pkg should no longer crash uncontrollably on network
  errors (#894).

• Fixed local open in interpreter (#887).

• Fix error regarding entry points that called other entry points
  which contained local functions (#895).

• Fix loading OpenCL kernels from a binary.

Fixed

• Fix a REPL regression that made it unable to handle overloaded
  types (such as numeric literals, oops).

• The uniqueness of a record is now the minimum of the uniqueness of
  any of its elements (#870).

• Bug in causality checking has been fixed (#872).

• Invariant memory allocations in scan/reduce operators are now supported.

• futhark run now performs more type checking on entry point input (#876).

• Compiled Futhark programs now check for EOF after the last input
  argument has been read (#877).

• Fixed a bug in loop type checking that prevented the result from
  ever aliasing the initial parameter values (#879).

Added

• Futhark now type-checks size annotations using a size-dependent
  type system.

• The parallel code generators can now handle bounds checking and
  other safety checks.

• Integer division by zero is now properly safety-checked and
  produces an error message.

• Integer exponentiation with negative exponent is now properly
  safety-checked and produces an error message.

• Serious effort has been put into improving type errors.

• reduce_by_index may be somewhat faster for complex operators on
  histograms that barely fit in local memory.

• Improved handling of in-place updates of multidimensional arrays
  nested in map. These are now properly parallelised.

• Added concat_to and flatten_to functions to prelude.

• Added indices function to the prelude.

• futhark check and all compilers now take a -w option for
  disabling warnings.

• futhark bench now accepts --pass-compiler-option.

• The integer modules now have mad_hi and mul_hi functions for
  getting the upper part of multiplications. Thanks to @porcuquine for the contribution!

• The f32 and f64 modules now also define sinh, cosh,
  tanh, asinh, acosh, and atanh functions.

• The f32 and f64 modules now also define fma and mad
  functions.

Removed

• Removed update, split2, intersperse, intercalate, pick,
  steps, and range from the prelude.

Changed

• "futlib" is now called "prelude", and it is now an error to
  import it explicitly.

Fixed

• Corrected address calculations in csharp backend.

• The C backends are now more careful about generating overflowing
  integer operations (since this is undefined behaviour in C, but
  defined in Futhark).

• futhark dataset no longer crashes uncontrollably when used
  incorrectly (#849).

Added

• The optimiser is now somewhat better at removing unnecessary
  copies of array slices.

• futhark bench and futhark test now take a --concurrency
  option for limiting how many threads are used for housekeeping
  tasks. Set this to a low value if you run out of memory.

• random test blocks are now allowed to contain integer literals
  with type suffixes.

• :frame <n> command for futhark repl for inspecting the stack.

• e :> t notation, which means the same as e : t for now, but
  will have looser constraints in the future.

• Size-lifted type abbreviations can be declared with type~ and
  size-lifted type parameters with '~. These currently have no
  significant difference from fully lifted types.

Changed

• Tuples are now 0-indexed (#821, which also includes a conversion
  script).

• Invalid ranges like 1..<0 now produce a run-time error instead
  of an empty array.

• Record updates (r with f = e) now require r to have a
  completely known type up to f. This is a restriction that will
  hopefully be lifted in the future.

• The backtrace format has changed to be innermost-first, like
  pretty much all other languages.

• Value specs must now explicitly quantify all sizes of function
  parameters. Instead of

  val sum: []t -> t
  

  you must write

  val sum [n]: [n]t -> t
  

• futhark test now once again numbers un-named data sets from 0
  rather than from 1. This fits a new general principle of always
  numbering from 0 in Futhark.

• Type abbreviations declared with type may no longer contain
  functions or anonymous sizes in their definition. Use type^ for
  these cases. Just a warning for now, but will be an error in the
  future.

Fixed

• Work around (probable) AMD OpenCL compiler bug for
  reduce_by_index operations with complex operators that require
  locking.

• Properly handle another ICE on parse errors in test stanzas (#819).

• futhark_context_new_with_command_queue() now actually works. Oops.

• Different scopes are now properly addressed during type inference
  (#838). Realistically, there will still be some missing cases.

Added

• New subcommand, futhark query, for looking up information about
  the name at some position in a file. Intended for editor
  integration.

• (Finally) automatic support for compute model 7.5 in the CUDA backend.

• Somewhat better performance for very large target arrays for
  reduce_by_index..

Fixed

• Fixed a slice-iota simplification bug (#813).

• Fixed defunctionalisation crash involving intrinsics (#814).

Added

• Stack traces are now multiline for better legibility.

Changed

• The empty(t) notation now specifies the type of the entire
  value (not just the element type), and requires dimension sizes
  when t is an array (e.g. empty(i32) is no longer allowed, you
  need for example empty([0]i32)).

• All input files are now assumed to be in UTF-8.

Fixed

• Fixed exponential-time behaviour for certain kernels with large
  arithmetic expressions (#805).

• futhark test and friends no longer crash when reporting some
  errors (#808).

• Fix uniqueness of loop results (#810).

Added

• Character literals can now be any integer type.

• The integer modules now have popc and clz functions.

• Tweaked inlining so that larger programs may now compile faster
  (observed about 20%).

• Pattern-matching on large sum typed-values taken from arrays may
  be a bit faster.

Fixed

• Various small fixes to type errors.

• All internal functions used in generated C code are now properly
  declared static.

• Fixed bugs when handling dimensions and aliases in type ascriptions.

Added

• New tool: futhark autotune, for tuning the threshold parameters
  used by incremental flattening. Based on work by Svend Lund
  Breddam, Simon Rotendahl, and Carl Mathias Graae Larsen.

• New tool: futhark dataget, for extracting test input data. Most
  will probably never use this.

• Programs compiled with the cuda backend now take options
  --default-group-size, --default-num-groups, and
  --default-tile-size.

• Segmented reduce_by_index are now substantially fasted for small
  histograms.

• New functions: f32.lerp and f64.lerp, for linear interpolation.

Fixed

• Fixes to aliasing of record updates.

• Fixed unnecessary array duplicates after coalescing optimisations.

• reduce_by_index nested in maps will no longer sometimes
  require huge amounts of memory.

• Source location now correct for unknown infix operators.

• Function parameters are no longer in scope of themselves (#798).

• Fixed a nasty out-of-bounds error in handling of irregular allocations.

• The floor/ceil functions in f32/f64 now handle infinities
  correctly (and are also faster).

• Using % on floats now computes fmod instead of crashing the compiler.

Added

• The internal representation of parallel constructs has been
  overhauled and many optimisations rewritten. The overall
  performance impact should be neutral on aggregate, but there may
  be changes for some programs (please report if so).

• Futhark now supports structurally typed sum types and pattern
  matching! This work was done by Robert Schenck. There remain
  some problems with arrays of sum types that themselves contain
  arrays.

• Significant reduction in compile time for some large programs.

• Manually specified type parameters need no longer be exhaustive.

• Mapped rotate is now simplified better. This can be
  particularly helpful for stencils with wraparound.

Removed

• The ~ prefix operator has been removed. ! has been extended
  to perform bitwise negation when applied to integers.

Changed

• The --futhark option for futhark bench and futhark test now
  defaults to the binary being used for the subcommands themselves.

• The legacy futhark -t option (which did the same as futhark check) has been removed.

• Lambdas now bind less tightly than type ascription.

• stream_map is now map_stream and stream_red is now
  reduce_stream.

Fixed

• futhark test now understands --no-tuning as it was always
  supposed to.

• futhark bench and futhark test now interpret --exclude in
  the same way.

• The Python and C# backends can now properly read binary boolean
  input.

Fixed

• Entry points whose types are opaque due to module ascription, yet
  whose representation is simple (scalars or arrays of scalars) were
  mistakely made non-opaque when compiled with --library. This
  has been fixed.

• The CUDA backend now supports default sizes in .tuning files.

• Loop interchange across multiple dimensions was broken in some cases (#767).

• The sequential C# backend now generates code that compiles (#772).

• The sequential Python backend now generates code that runs (#765).

Added

• Segmented scans are a good bit faster.

• reduce_by_index has received a new implementation that uses
  local memory, and is now often a good bit faster when the target
  array is not too large.

• The f32 and f64 modules now contain gamma and lgamma
  functions. At present these do not work in the C# backend.

• Some instances of reduce with vectorised operators (e.g. map2 (+)) are orders of magnitude faster than before.

• Memory usage is now lower on some programs (specifically the ones
  that have large maps with internal intermediate arrays).

Removed

• Size parameters (not annotations) are no longer permitted
  directly in let and loop bindings, nor in lambdas. You are
  likely not affected (except for the stream constructs; see
  below). Few people used this.

Changed

• The array creation functions exported by generated C code now take
  int64_t arguments for the shape, rather than int. This is in
  line with what the shape functions return.

• The types for stream_map, stream_map_per, stream_red, and
  stream_red_per have been changed, such that the chunk function
  now takes the chunk size as the first argument.

Fixed

• Fixes to reading values under Python 3.

• The type of a variable can now be deduced from its use as a size
  annotation.

• The code generated by the C-based backends is now also compilable
  as C++.

• Fix memory corruption bug that would occur on very large segmented
  reductions (large segments, and many of them).

Added

• reduce_by_index is now a good bit faster on operators whose
  arguments are two 32-bit values.

• The type checker warns on size annotations for function parameters
  and return types that will not be visible from the outside,
  because they refer to names nested inside tuples or records. For
  example, the function

  let f (n: i32, m: i32): [n][m]i32 = ...
  

  will cause such a warning. It should instead be written

  let f (n: i32) (m: i32): [n][m]i32 = ...
  

• A new library function
  futhark_context_config_select_device_interactively() has been
  added.

Fixed

• Fix reading and writing of binary files for C-compiled executables
  on Windows.

• Fixed a couple of overly strict internal sanity checks related to
  in-place updates (#735, #736).

• Fixed a couple of convoluted defunctorisation bugs (#739).

Added

• Using definitions from the intrinsic module outside the prelude
  now results in a warning.

• reduce_by_index with vectorised operators (e.g. map2 (+)) is
  orders of magnitude faster than before.

• Executables generated with the pyopencl backend now support the
  options --default-tile-size, --default-group-size,
  --default-num-groups, --default-threshold, and --size.

• Executables generated with c and opencl now print a help text
  if run with invalid options. The py and pyopencl backends
  already did this.

• Generated executables now support a --tuning flag for passing
  many tuned sizes in a file.

• Executables generated with the cuda backend now take an
  --nvrtc-option option.

• Executables generated with the opencl backend now take a
  --build-option option.

Removed

• The old futhark-* executables have been removed.

Changed

• If an array is passed for a function parameter of a polymorphic
  type, all arrays passed for parameters of that type must have the
  same shape. For example, given a function

  let pair 't (x: t) (y: t) = (x, y)
  

  The application pair [1] [2,3] will now fail at run-time.

• futhark test now numbers un-named data sets from 1 rather than
  0. This only affects the text output and the generated JSON
  files, and fits the tuple element ordering in Futhark.

• String literals are now of type []u8 and contain UTF-8 encoded
  bytes.

Fixed

• An significant problematic interaction between empty arrays and
  inner size declarations has been closed (#714). This follows a
  range of lesser empty-array fixes from 0.9.1.

• futhark datacmp now prints to stdout, not stderr.

• Fixed a major potential out-of-bounds access when sequentialising
  reduce_by_index (in most cases the bug was hidden by subsequent
  C compiler optimisations).

• The result of an anonymous function is now also forbidden from
  aliasing a global variable, just as with named functions.

• Parallel scans now work correctly when using a CPU OpenCL
  implementation.

• reduce_by_index was broken on newer NVIDIA GPUs when using fancy
  operators. This has been fixed.

Added

• futhark cuda: a new CUDA backend by Jakob Stokholm Bertelsen.

• New command for comparing data files: futhark datacmp.

• An :mtype command for futhark repl that shows the type of a
  module expression.

• futhark run takes a -w option for disabling warnings.

Changed

• Major command reorganisation: all Futhark programs have been
  combined into a single all-powerful futhark program. Instead of
  e.g. futhark-foo, use futhark foo. Wrappers will be kept
  around under the old names for a little while. futharki has
  been split into two commands: futhark repl and futhark run.
  Also, py has become python and cs has become csharp, but
  pyopencl and csopencl have remained as they were.

• The result of a function is now forbidden from aliasing a global
  variable. Surprisingly little code is affected by this.

• A global definition may not be ascribed a unique type. This never
  had any effect in the first place, but now the compiler will
  explicitly complain.

• Source spans are now printed in a slightly different format, with
  ending the line number omitted when it is the same as the start
  line number.

Fixed

• futharki now reports source locations of trace expressions
  properly.

• The type checker now properly complains if you try to define a
  type abbreviation that has unused size parameters.

Added

• Now warns when /futlib/... files are redundantly imported.

• futharki now prints warnings for files that are ":load"ed.

• The compiler now warns when entry points are declared with types
  that will become unnamed and opaque, and thus impossible to
  provide from the outside.

• Type variables invented by the type checker will now have a
  unicode subscript to distinguish them from type parameters
  originating in the source code.

• futhark-test and futhark-bench now support generating random
  test data.

• The library backends now generate proper names for arrays of
  opaque values.

• The parser now permits empty programs.

• Most transpositions are now a good bit faster, especially on
  NVIDIA GPUs.

Removed

• The <- symbol can no longer be used for in-place updates and
  record updates (deprecated in 0.7.3).

Changed

• Entry points that accept a single tuple-typed parameter are no
  longer silently rewritten to accept multiple parameters.

Fixed

• The :type command in futharki can now handle polymorphic
  expressions (#669).

• Fixed serious bug related to chaining record updates.

• Fixed type inference of record fields (#677).

• futharki no longer goes in an infinite loop if a for loop
  contains a negative upper bound.

• Overloaded number types can no longer carry aliases (#682).