# OpenCL conformance

## Conformance related CMake options

- `-DENABLE_CONFORMANCE=ON/OFF` This is mostly related to the kernel library (the runtime is always built to be conformant on x86). Defaults to ON. This option by itself does not guarantee OpenCL-conformant build; it merely ensures that a build fails if some options which would result in non-conformant kernel library are given.

  Non-conformant kernel library might be somewhat faster, at the expense of precision and/or range. Note that conformance was tested only on certain hardware and software (Linux, x86-64, CPU with AVX & FMA instructions).

## How to run the conformance test suite on your hardware

First you need to enable the suite in the pocl’s external test suite set. This is done by adding switch `-DENABLE_TESTSUITES=conformance` to the cmake command line. After this `make prepare_examples` fetches and prepares the conformance suite for testing.

To run a shortened version of the conformance suite, run: `ctest -L conformance_suite_mini` This might take a few hours on slow hardware. There is also a `conformance_suite_micro` label, which takes about 20-30 minutes on slow hardware.

To run the full conformance testsuite, run: `ctest -L conformance_suite_full` Note that this can take a week to finish on slow hardware, and about a day on relatively fast hardware (6C/12T Intel or equivalent).

## Known issues with the conformance testsuite

- a few tests from `basic/test_basic` may fail / segfault because they request a huge amount of memory for buffers.

- compiler_defines_for_extensions from `compiler/test_compiler` might fail because cl_khr_spir extension is not recognized with OpenCL 1.2 - officially it’s only recognized since OpenCL 2.0.

- a few tests from `conversions/test_conversions` may report failures. This is likely a bug in the test; the same test from branch cl20_trunk of CTS passes.

- some tests from `relationals/test_relationals` can fail with specific LLVM versions, this is an LLVM bug, fixed in LLVM 13.

- `math_brute_force/bruteforce` tests may occasionally fail with an empty build log, this is a bug in CTS. See pocl issue #614. `export CL_TEST_SINGLE_THREADED=1` might help.

- a few tests may run much faster if you limit the reported Global memory size with POCL_MEMORY_LIMIT env var. In particular, “kernel_image_methods” test with “max_images” argument.

- two tests in `api/test_api` fail with LLVM 5.0 because of LLVM commit 1c1154229a41b688f9:

  > `[OpenCL] Do not generate "kernel_arg_type_qual" metadata for non-pointer args`

  This is a bug in CTS, which tests for non-pointer type qualifiers, not in pocl. See:

  https://www.khronos.org/registry/OpenCL/specs/opencl-1.2.pdf page 169:

  `CL_KERNEL_ARG_TYPE_VOLATILE` is returned if the argument is a pointer and the referenced type is declared with the volatile qualifier. Similarly, `CL_KERNEL_ARG_TYPE_RESTRICT` or `CL_KERNEL_ARG_TYPE_CONST` is returned if the argument is a pointer and the referenced type is declared with the restrict or const qualifier

## Known issues in pocl / things to be aware of

- Integer division by zero. OpenCL 1.2 specification requires that division by zero on integers results in undefined values, instead of raising exceptions. This requires pocl to install a handler of SIGFPE. Unfortunately signal handlers are per-process not per-thread, and pocl drivers do not run in a separate process, which means that integer division by zero will not raise SIGFPE for the entire pocl library and also the user’s program. The handler may be disabled by setting the env variable POCL_SIGFPE_HANDLER to 0. Note that this is currently only relevant for x86(-64) + Linux, on all other systems this issue is not handled in any way (thus Pocl is likely non-conformant there).

- Several options to clBuildProgram() are accepted but currently have no effect. This is related mostly to optimization options like -cl-fast-relaxed-math. The -cl-denorms-are-zero and -cl-fp32-correctly-rounded-divide-sqrt options are honored.

- Many of `native_` and `half_` variants of kernel library functions are mapped to the “full” variants.

- the optional OpenGL / D3D extensions are not supported. There is experimental support for SPIR

- clUnloadCompiler() only actually unload LLVM after all programs & kernels have been released.

- clSetUserEventStatus() called with negative status. The Spec leaves the behaviour in this case as “implementation defined”, and this part of pocl is only very lightly tested by the conformance tests. clSetUserEventStatus() called with CL_COMPLETE works as expected, and is heavily used by the conversions conformance test.

## Conformance tests results (kernel library precision) on tested hardware

Note that it’s impossible to test double precision on the entire range, therefore the results may vary.

### x86-64 CPU with AVX2+FMA, LLVM 4.0, tested on Nov 1, 2017

NAME | Worst ULP | WHERE
--- | --- | ---
add | 0.00 | {0x0p+0, 0x0p+0}
addD | 0.00 | {0x0p+0, 0x0p+0}
assignment | 0.00 | 0x0p+0
assignmentD | 0.00 | 0x0p+0
cbrt | 0.50 | -0x1.5629d2p+116
cbrtD | 0.59 | 0x1.0000000000136p+1022
ceil | 0.00 | 0x0p+0
ceilD | 0.00 | 0x0p+0
copysign | 0.00 | {0x0p+0, 0x0p+0}
copysignD | 0.00 | {0x0p+0, 0x0p+0}
cos | 2.37 | 0x1.1338ccp+20
cosD | 2.27 | -0x1.d10000000074p+380
cosh | 2.41 | -0x1.602166p+2
coshD | 1.43 | -0x1.98000000003efp+5
cospi | 1.94 | 0x1.d73b56p-2
cospiD | 2.46 | -0x1.adffffffffa91p-2
divide | 0.00 | {0x0p+0, 0x0p+0}
divideD | 0.00 | {0x0p+0, 0x0p+0}
exp | 0.95 | -0x1.762532p+2
expD | 0.94 | 0x1.2f0000000023dp+7
exp10 | 0.79 | -0x1.309022p+5
exp10D | 0.64 | -0x1.34ffffffffcc9p+8
exp2 | 0.79 | -0x1.fa3d0ep+6
exp2D | 0.75 | -0x1.ff00000000417p+9
expm1 | 1.00 | -0x1.7a0002p-25
expm1D | 0.99 | -0x1.26p+5
fabs | 0.00 | 0x0p+0
fabsD | 0.00 | 0x0p+0
fdim | 0.00 | {0x0p+0, 0x0p+0}
fdimD | 0.00 | {0x0p+0, 0x0p+0}
floor | 0.00 | 0x0p+0
floorD | 0.00 | 0x0p+0
fma | 0.00 | {0x0p+0, 0x0p+0, 0x0p+0}
fmaD | 0.00 | {0x0p+0, 0x0p+0, 0x0p+0}
fmax | 0.00 | {0x0p+0, 0x0p+0}
fmaxD | 0.00 | {0x0p+0, 0x0p+0}
fmin | 0.00 | {0x0p+0, 0x0p+0}
fminD | 0.00 | {0x0p+0, 0x0p+0}
fmod | 0.00 | {0x0p+0, 0x0p+0}
fmodD | 0.00 | {0x0p+0, 0x0p+0}
fract | { 0.00, 0.00} | {0x0p+0, 0x0p+0}
fractD | { 0.00, 0.00} | {0x0p+0, 0x0p+0}
frexp | { 0.00, 0} | 0x0p+0
frexpD | { 0.00, 0} | 0x0p+0
hypot | 1.93 | {0x1.17c998p-127, -0x1.5fedb8p-127}
hypotD | 1.73 | {0x1.5d2ebeed7663cp-1022, 0x1.67457048a2318p-1022}
ldexp | 0.00 | {0x0p+0, 0}
ldexpD | 0.00 | {0x0p+0, 0}
log10 | 0.50 | 0x1.7fee2ep-1
log10D | 0.50 | 0x1.9100000000639p+1022
log | 0.63 | 0x1.7fcb3ep-1
logD | 0.75 | 0x1.7d00000000381p+0
log1p | 1.00 | -0x1.fa0002p-126
log1pD | 1.00 | -0x1.e000000000001p-1022
log2 | 0.59 | 0x1.1107a2p+0
log2D | 0.72 | 0x1.120000000063dp+0
logb | 0.00 | 0x0p+0
logbD | 0.00 | 0x0p+0
mad | 0.00 | {0x0p+0, 0x0p+0, 0x0p+0} no ULP check
madD | 0.00 | {0x0p+0, 0x0p+0, 0x0p+0} no ULP check
maxmag | 0.00 | {0x0p+0, 0x0p+0}
maxmagD | 0.00 | {0x0p+0, 0x0p+0}
minmag | 0.00 | {0x0p+0, 0x0p+0}
minmagD | 0.00 | {0x0p+0, 0x0p+0}
modf | { 0.00, 0.00} | {0x0p+0, 0x0p+0}
modfD | { 0.00, 0.00} | {0x0p+0, 0x0p+0}
multiply | 0.00 | {0x0p+0, 0x0p+0}
multiplyD | 0.00 | {0x0p+0, 0x0p+0}
nan | 0.00 | 0x0p+0
nanD | 0.00 | 0x0p+0
nextafter | 0.00 | {0x0p+0, 0x0p+0}
nextafterD | 0.00 | {0x0p+0, 0x0p+0}
pow | 0.82 | {0x1.91237cp-1, 0x1.4da146p+8}
powD | 0.80 | {0x1.2bfb4b18164c9p+65, -0x1.b78438ae9c3bdp-8}
pown | 0.65 | {-0x1.9p+6, -2}
pownD | 0.62 | {-0x1.7ffffffffffffp+1, 3}
powr | 0.82 | {0x1.91237cp-1, 0x1.4da146p+8}
powrD | 0.80 | {0x1.2bfb4b18164c9p+65, -0x1.b78438ae9c3bdp-8}
remainder | 0.00 | {0x0p+0, 0x0p+0}
remainderD | 0.00 | {0x0p+0, 0x0p+0}
remquo | { 0.00, 0} | 0x0p+0
remquoD | { 0.00, 0} | 0x0p+0
rint | 0.00 | 0x0p+0
rintD | 0.00 | 0x0p+0
rootn | 0.69 | {-0x1.e2fe6ep-74, -141}
rootnD | 0.68 | {-0x1.8000000000001p+1, 3}
round | 0.00 | 0x0p+0
roundD | 0.00 | 0x0p+0
rsqrt | 1.49 | 0x1.019566p+124
rsqrtD | 1.49 | 0x1.01ffffffffa39p+1016
sin | 2.48 | -0x1.09f07ap+21
sinD | 1.87 | -0x1.f2fffffffffbap+32
sincos | { 2.48, 2.37} | {0x1.09f07ap+21, 0x1.1338ccp+20}
sincosD | { 1.87, 2.27} | {0x1.f2fffffffffbap+32, 0x1.d10000000074p+380}
sinh | 2.32 | 0x1.e76078p+2
sinhD | 1.53 | -0x1.3100000000278p+4
sinpi | 2.13 | -0x1.45f3ep-9
sinpiD | 2.50 | -0x1.46000000000dap-7
sqrt | 0.00 | 0x0p+0
sqrtD | 0.00 | 0x0p+0
subtract | 0.00 | {0x0p+0, 0x0p+0}
subtractD | 0.00 | {0x0p+0, 0x0p+0}
tan | 4.35 | -0x1.b4eba2p+22
tanD | 4.00 | -0x1.2f000000003edp+333
tanh | 1.18 | -0x1.ca742ap-1
tanhD | 1.19 | 0x1.f400000000395p-1
tanpi | 4.21 | -0x1.f99d16p-3
tanpiD | 4.09 | 0x1.f6000000001d3p-3
trunc | 0.00 | 0x0p+0
truncD | 0.00 | 0x0p+0