Not sure how to fix this error:

/usr/bin/ld: /usr/bin/ld: DWARF error: invalid or unhandled FORM value: 0x25
Objects/floatobject.o: in function `PyFloat_Pack2':
floatobject.c:(.text.PyFloat_Pack2[PyFloat_Pack2]+0x32): undefined reference to `__truncdfhf2'
clang: error: linker command failed with exit code 1 (use -v to see invocation)

CC @StanFromIreland (fuzzers)

The configure probe only tests a compile-time _Float16 constant, so it reports "yes" in the OSS-Fuzz Docker container where clang accepts the type but the container's pre-GCC-12 libgcc lacks __truncdfhf2 which is the runtime helper the PyFloat_Pack2 double to _Float16 conversion links against. I suggest you make configure do a runtime double to _Float16 conversion.

I suggest you make configure do a runtime double to _Float16 conversion.

Good idea, that works.

🤖 New build scheduled with the buildbot fleet by @skirpichev for commit ac38cb8 🤖

Results will be shown at:

https://buildbot.python.org/all/#/grid?branch=refs%2Fpull%2F154796%2Fmerge

If you want to schedule another build, you need to add the 🔨 test-with-buildbots label again.

@skirpichev: Did you close your PR on purpose?

Did you close your PR on purpose?

Yes, this lacks benchmarks. I hope someone will continue this.

@hpkfft, maybe you can check performance for a simple pyperf-based benchmark?

import pyperf
from struct import pack, unpack

x = 3.140625
bx = struct.pack('e', x)

runner = pyperf.Runner()
runner.bench_func('pack("e", 3.140625)', pack, "e", x)
runner.bench_func('unpack("e", b"HB")', unpack, "e", bx)

Using gcc 14.2.0 and ./configure:

main:
pack("e", 3.140625): Mean +- std dev: 56.2 ns +- 1.1 ns
unpack("e", b"HB"): Mean +- std dev: 64.8 ns +- 1.2 ns

patch:
pack("e", 3.140625): Mean +- std dev: 51.9 ns +- 0.8 ns
unpack("e", b"HB"): Mean +- std dev: 59.0 ns +- 1.0 ns

Using ./configure --enable-optimizations:

main:
pack("e", 3.140625): Mean +- std dev: 37.7 ns +- 0.2 ns
unpack("e", b"HB"): Mean +- std dev: 46.1 ns +- 0.4 ns

patch:
pack("e", 3.140625): Mean +- std dev: 38.2 ns +- 0.3 ns
unpack("e", b"HB"): Mean +- std dev: 43.6 ns +- 0.5 ns

Interesting. Does the training input for PGO have NaNs in it? If so, maybe it shouldn't....

Does the training input for PGO have NaNs in it?

Yes, PGO set of tests lacks test_capi, but test_struct.py is selected (see Lib/test/libregrtest/pgo.py). That one has various tests, including half-float NaNs. You can filter out some tests for PGO by @skip_if_pgo_task. (Usually we do this for expensive tests.)

Apparently, CPython runtime overhead dominated in the above benchmark. For C code I got ~2x speedup, like you above. I'll try to repeat that with some benchmarking framework.

Anyway, lets reopen this.

Merged, thanks.

I didn't close #153740 since it seems like more changes are planned.

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot wasm32-wasi 3.x (tier-2) has failed when building commit e7ef46a.

What do you need to do:

1. Don't panic.
2. Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/#/builders/1046/builds/12907) and take a look at the build logs.
4. Check if the failure is related to this commit (e7ef46a) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/#/builders/1046/builds/12907

Failed tests:

• test_zipfile

Failed subtests:

• test_append_to_concatenated_zip_file - test.test_zipfile.test_core.StoredTestsWithSourceFile.test_append_to_concatenated_zip_file
• test_write_filtered_python_package - test.test_zipfile.test_core.PyZipFileTests.test_write_filtered_python_package

Summary of the results of the build (if available):

==

Traceback (most recent call last):
  File "/Lib/test/test_zipfile/test_core.py", line 3649, in test_write_filtered_python_package
    with TemporaryFile() as t, zipfile.PyZipFile(t, "w") as zipfp:
                               ~~~~~~~~~~~~~~~~~^^^^^^^^
  File "/Lib/zipfile/__init__.py", line 2026, in __exit__
    self.close()
    ~~~~~~~~~~^^
  File "/Lib/zipfile/__init__.py", line 2667, in close
    self.fp.seek(self.start_dir)
    ~~~~~~~~~~~~^^^^^^^^^^^^^^^^
OSError: [Errno 51] No space left on device


Traceback (most recent call last):
  File "/Lib/test/test_zipfile/test_core.py", line 3654, in test_write_filtered_python_package
    zipfp.writepy(packagedir)
    ~~~~~~~~~~~~~^^^^^^^^^^^^
  File "/Lib/zipfile/__init__.py", line 2830, in writepy
    self.writepy(path, basename,
    ~~~~~~~~~~~~^^^^^^^^^^^^^^^^
                 filterfunc=filterfunc)  # Recursive call
                 ^^^^^^^^^^^^^^^^^^^^^^
  File "/Lib/zipfile/__init__.py", line 2840, in writepy
    self.writestr(arcname, bytecode)
    ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^
  File "/Lib/zipfile/__init__.py", line 2605, in writestr
    with self.open(zinfo, mode='w') as dest:
         ~~~~~~~~~^^^^^^^^^^^^^^^^^
  File "/Lib/zipfile/__init__.py", line 1423, in close
    self._fileobj.seek(self._zinfo.header_offset)
    ~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^
OSError: [Errno 51] No space left on device


Traceback (most recent call last):
  File "/Lib/test/test_zipfile/test_core.py", line 3649, in test_write_filtered_python_package
    with TemporaryFile() as t, zipfile.PyZipFile(t, "w") as zipfp:
         ~~~~~~~~~~~~~^^
OSError: [Errno 51] No space left on device


Traceback (most recent call last):
  File "/Lib/test/test_zipfile/test_core.py", line 572, in test_append_to_concatenated_zip_file
    f.write(data)
    ~~~~~~~^^^^^^
OSError: [Errno 51] No space left on device