.. role:: ref(emphasis)

.. _futhark-test(1):

============
futhark-test
============

SYNOPSIS
========

futhark test [options...] infiles...

DESCRIPTION
===========

Test Futhark programs based on input/output datasets.  All contained
``.fut`` files within a given directory are considered.  By default,
tests are carried out with compiled code.  This can be changed with
the ``-i`` option.

A Futhark test program is an ordinary Futhark program, with at least
one test block describing input/output test cases and possibly other
options.  The last line must end in a newline.  A test block consists
of commented-out text with the following overall format::

  description
  ==
  cases...

The ``description`` is an arbitrary (and possibly multiline)
human-readable explanation of the test program.  It is separated from
the test cases by a line containing just ``==``.  Any comment starting
at the beginning of the line, and containing a line consisting of just
``==``, will be considered a test block.  The format of a test case is
as follows::

  [tags { tags... }]
  [entry: names...]
  ["name..."] [compiled|nobench|random|script] input ({ values... } | @ filename)
  output { values... } | auto output | error: regex

If a test case begins with a quoted string, that string is reported as
the dataset name, including in the JSON file produced by
:ref:`futhark-bench(1)`.  If no name is provided, one is automatically
generated.  The name must be unique across all test cases.

If ``compiled`` is present before the ``input`` keyword, this test
case will never be passed to the interpreter.  This is useful for test
cases that are annoyingly slow to interpret.  The ``nobench`` keyword
is for data sets that are too small to be worth benchmarking, and only
has meaning to :ref:`futhark-bench(1)`.

If ``input`` is preceded by ``random``, the text between the curly
braces must consist of a sequence of Futhark types, including sizes in
the case of arrays.  When ``futhark test`` is run, a file located in a
``data/`` subdirectory, containing values of the indicated types and
shapes is, automatically constructed with :ref:`futhark-dataset(1)`.
Apart from sizes, integer constants (with or without type suffix), and
floating-point constants (always with type suffix) are also permitted.

If ``input`` is preceded by ``script``, the text between the curly
braces is interpreted as a FutharkScript expression (see
:ref:`futhark-literate(1)`), which is executed to generate the input.
It must use only functions explicitly declared as entry points. If the
expression produces an *n*-element tuple, it will be unpacked and its
components passed as *n* distinct arguments to the test function. The
only builtin functions supported are ``$loaddata`` and ``$loadbytes``.

If ``input`` is followed by an ``@`` and a file name (which must not
contain any whitespace) instead of curly braces, values will be read
from the indicated file.  This is recommended for large data sets.
This notation cannot be used with ``random`` input.  With ``script
input``, the file contents will be interpreted as a FutharkScript
expression.

After the ``input`` block, the expected result of the test case is
written as either ``output`` followed by another block of values, or
``error:`` followed by a regex indicating an expected run-time error.
If neither ``output`` nor ``error`` is given, the program will be
expected to execute succesfully, but its output will not be validated.

If ``output`` is preceded by ``auto`` (as in ``auto output``), the
expected values are automatically generated by compiling the program
with ``futhark c`` and recording its result for the given input (which
must not fail).  This is usually only useful for testing or
benchmarking alternative compilers, and not for testing the
correctness of Futhark programs.  This currently does not work for
``script`` inputs.

Alternatively, instead of input-output pairs, the test cases can
simply be a description of an expected compile time type error::

  error: regex

This is used to test the type checker.

Tuple syntax is not supported when specifying input and output values.
Instead, you can write an N-tuple as its constituent N values.  Beware
of syntax errors in the values - the errors reported by
``futhark test`` are very poor.

An optional tags specification is permitted in the first test block.
This section can contain arbitrary tags that classify the benchmark::

  tags { names... }

Tag are sequences of alphanumeric characters, dashes, and underscores,
with each tag seperated by whitespace.  Any program with the
``disable`` tag is ignored by ``futhark test``.

Another optional directive is ``entry``, which specifies the entry
point to be used for testing.  This is useful for writing programs
that test libraries with multiple entry points.  Multiple entry points
can be specified on the same line by separating them with space, and
they will all be tested with the same input/output pairs.  The
``entry`` directive affects subsequent input-output pairs in the same
comment block, and may only be present immediately preceding these
input-output pairs.  If no ``entry`` is given, ``main`` is assumed.
See below for an example.

For many usage examples, see the ``tests`` directory in the
Futhark source directory.  A simple example can be found in
``EXAMPLES`` below.

OPTIONS
=======

--backend=program

  The backend used when compiling Futhark programs (without leading
  ``futhark``, e.g. just ``opencl``).

--cache-extension=EXTENSION

  For a program ``foo.fut``, pass ``--cache-file foo.fut.EXTENSION``.
  By default, ``--cache-file`` is not passed.

-c
  Only run compiled code - do not run the interpreter.  This is the
  default.

-C
  Compile the programs, but do not run them.

--concurrency=NUM

  The number of tests to run concurrently.  Defaults to the number of
  (hyper-)cores available.

--exclude=tag

  Do not run test cases that contain the given tag.  Cases marked with
  "disable" are ignored by default, as are cases marked "no_foo",
  where *foo* is the backend used.

-i
  Test with the interpreter.

-I
  Pass the program through the compiler frontend, but do not run them.
  This is only useful for testing the Futhark compiler itself.

-t
  Type-check the programs, but do not run them.

--futhark=program

  The program used to perform operations (eg. compilation).  Defaults
  to the binary running ``futhark test`` itself.

--no-terminal
  Print each result on a line by itself, without line buffering.

--no-tuning

  Do not look for tuning files.

--pass-option=opt

  Pass an option to benchmark programs that are being run.  For
  example, we might want to run OpenCL programs on a specific device::

    futhark test prog.fut --backend=opencl --pass-option=-dHawaii

--pass-compiler-option=opt

  Pass an extra option to the compiler when compiling the programs.

--runner=program

  If set to a non-empty string, compiled programs are not run
  directly, but instead the indicated *program* is run with its first
  argument being the path to the compiled Futhark program.  This is
  useful for compilation targets that cannot be executed directly (as
  with :ref:`futhark-pyopencl(1)` on some platforms), or when you wish
  to run the program on a remote machine.

--tuning=EXTENSION

  For each program being run, look for a tuning file with this
  extension, which is suffixed to the name of the program.  For
  example, given ``--tuning=tuning`` (the default), the program
  ``foo.fut`` will be passed the tuning file ``foo.fut.tuning`` if it
  exists.

ENVIRONMENT VARIABLES
=====================

``TMPDIR``

  Directory used for temporary files such as gunzipped datasets and
  log files.

EXAMPLES
========

The following program tests simple indexing and bounds checking::

  -- Test simple indexing of an array.
  -- ==
  -- tags { firsttag secondtag }
  -- input { [4,3,2,1] 1i64 }
  -- output { 3 }
  -- input { [4,3,2,1] 5i64 }
  -- error: Error*

  let main (a: []i32) (i: i64): i32 =
    a[i]

The following program contains two entry points, both of which are
tested::

  let add (x: i32) (y: i32): i32 = x + y

  -- Test the add1 function.
  -- ==
  -- entry: add1
  -- input { 1 } output { 2 }

  entry add1 (x: i32): i32 = add x 1

  -- Test the sub1 function.
  -- ==
  -- entry: sub1
  -- input { 1 } output { 0 }

  entry sub1 (x: i32): i32 = add x (-1)

The following program contains an entry point that is tested with
randomly generated data::

  -- ==
  -- random input { [100]i32 [100]i32 } auto output
  -- random input { [1000]i32 [1000]i32 } auto output

  let main xs ys = i32.product (map2 (*) xs ys)


SEE ALSO
========

:ref:`futhark-bench(1)`, :ref:`futhark-repl(1)`