Remove `make_iter_mode` and refactor access mode resolution by danhoeflinger · Pull Request #2551 · uxlfoundation/oneDPL

danhoeflinger · 2025-12-29T17:26:23Z

Summary

Move access mode resolution logic from scattered make_iter_mode calls to the leaf-level __get_sycl_range when processing sycl_iterator. This centralizes the mode resolution logic and ensures it properly recurses through nested iterator types.

Changes

Removed make_iter_mode pattern:

Removed iter_mode struct and make_iter_mode function from parallel_backend_sycl.h
Removed all make_iter_mode wrapper calls from algorithm implementations in algorithm_impl_hetero.h and async_impl_hetero.h

Refactored iter_mode_resolver:

Moved to utils_ranges_sycl.h as the authoritative location
Primary template is now undefined (SFINAE-friendly) instead of using static_assert
Added __is_iter_mode_resolvable_v trait for testable compile-time compatibility checking
Added third template parameter noInit to track whether algorithm allows skipping host→device copy

Fixed mode compatibility logic:

Removed incorrect specializations that claimed read or write iterators could satisfy read_write algorithm requirements
Removed incorrect specializations allowing discard_* modes with algorithms that dont have no_init
Valid combinations: exact match, read_write→read, read_write→write, discard_read_write -> * (only when no_init=true), discard_write -> write (only when no_init=true).

Connected no_init property to accessors:

all_view now includes a template argument for _NoInit which connects to actual sycl accessor
Now properly uses backend buffer accessor system with no_init property when appropriate

NOTE: These changes could result in new build error for users where it was not before if it was relying upon improperly matched behavior. It seems like this could've resulted in silent problems or even segfaults in kernels where algorithms don't get the access modes they need.

Added tests:

test_is_iter_mode_resolvable_v() covering valid and invalid mode combinations

Targeted to land after #2519 and #2549 (final episode in the __get_sycl_range refactor trilogy)
Resolves Issue #2550

Future work:
There may be some opportunity to utilize no_init for our temporary buffers, though I'm not sure if that will result in any real savings, as the system should know when there is nothing to transfer to the device.

Copilot

Pull request overview

This PR centralizes access mode resolution logic for SYCL iterators by moving it from scattered make_iter_mode calls to the leaf-level __get_sycl_range implementation. The refactoring removes the iter_mode struct and make_iter_mode function, replacing them with compile-time mode resolution directly in __process_input_iter for sycl_iterator types.

Key Changes:

Removed make_iter_mode pattern and moved access mode resolution into __get_sycl_range's sycl_iterator specialization
Fixed incorrect mode compatibility logic (e.g., read/write iterators can no longer satisfy read_write algorithm requirements)
Added comprehensive test coverage for mode resolution compatibility checking

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
`parallel_backend_sycl.h`	Removed deprecated `iter_mode_resolver`, `iter_mode` struct, and `make_iter_mode` function (~130 lines)
`utils_ranges_sycl.h`	Added refactored `iter_mode_resolver` with corrected compatibility logic and new `sycl_iterator` specialization in `__process_input_iter`
`algorithm_impl_hetero.h`	Removed `make_iter_mode` wrapper calls from fill, generate, partition_copy, inplace_merge, and partial_sort patterns
`async_impl_hetero.h`	Removed `make_iter_mode` wrapper calls from async fill pattern
`get_sycl_range.pass.cpp`	Added `test_is_iter_mode_resolvable_v` test function covering valid/invalid mode combinations

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Copilot

Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated 5 comments.

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include/oneapi/dpl/pstl/hetero/dpcpp/utils_ranges_sycl.h

MikeDvorskiy · 2026-01-12T16:35:40Z

At first glance, I am in favor of the changes. I didn’t like iter_mode/iter_mode_resolver 3–4 years ago, since I had noticed needless structures. I’ve been wanting to cut these structures out of the oneDPL code for a long time.

Thank you!

SergeyKopienko · 2026-01-13T10:02:16Z

include/oneapi/dpl/pstl/algorithm_impl.h

                //try searching for the first element which not equal to *__b
                if (__b != __first1)
-                    __b += __internal::__pstl_upper_bound(__b, _DifferenceType1{0}, __last1 - __b, __b, __comp, __proj1, __proj1);
+                    __b += __internal::__pstl_upper_bound(__b, _DifferenceType1{0}, __last1 - __b, __b, __comp, __proj1,


Let's save the previous format.

removed these formatting only changes. thanks.

SergeyKopienko · 2026-01-13T10:02:20Z

include/oneapi/dpl/pstl/algorithm_impl.h

                //try searching for the first element which not equal to *__e
                if (__e != __last1)
-                    __e += __internal::__pstl_upper_bound(__e, _DifferenceType1{0}, __last1 - __e, __e, __comp, __proj1, __proj1);
+                    __e += __internal::__pstl_upper_bound(__e, _DifferenceType1{0}, __last1 - __e, __e, __comp, __proj1,


Let's save the previous format.

removed these formatting only changes. thanks.

fix access modes for uninitialized apis remove unnecessary pattern Signed-off-by: Dan Hoeflinger <dan.hoeflinger@intel.com>

Signed-off-by: Dan Hoeflinger <dan.hoeflinger@intel.com>

…emove_make_iter_mode

danhoeflinger requested review from MikeDvorskiy, SergeyKopienko and Copilot December 29, 2025 17:26

Copilot AI reviewed Dec 29, 2025

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danhoeflinger force-pushed the dev/dhoeflin/remove_make_iter_mode branch from e4040d0 to 5bf81d6 Compare December 31, 2025 21:50

danhoeflinger requested a review from Copilot January 2, 2026 12:56

Copilot AI reviewed Jan 2, 2026

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danhoeflinger requested review from akukanov, dmitriy-sobolev, mmichel11 and timmiesmith January 2, 2026 15:37

danhoeflinger linked an issue Jan 2, 2026 that may be closed by this pull request

iter_mode / make_iter_mode issues and potential cleanup #2550

Open

danhoeflinger force-pushed the dev/dhoeflin/unitialized_refactors branch from 36ae926 to 03c83d1 Compare January 2, 2026 22:33

danhoeflinger force-pushed the dev/dhoeflin/remove_make_iter_mode branch from 044c431 to 728d20c Compare January 2, 2026 22:35

danhoeflinger mentioned this pull request Jan 5, 2026

Refactor __get_sycl_range to align with sycl #2519

Merged

danhoeflinger added this to the 2022.12.0 milestone Jan 5, 2026

danhoeflinger force-pushed the dev/dhoeflin/unitialized_refactors branch from 03c83d1 to 08eb860 Compare January 5, 2026 18:12

danhoeflinger force-pushed the dev/dhoeflin/remove_make_iter_mode branch from 808f0de to be5fe30 Compare January 5, 2026 18:13

SergeyKopienko reviewed Jan 13, 2026

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danhoeflinger force-pushed the dev/dhoeflin/unitialized_refactors branch from 08eb860 to f02042d Compare January 13, 2026 13:50

danhoeflinger force-pushed the dev/dhoeflin/remove_make_iter_mode branch from be5fe30 to c0563c6 Compare January 13, 2026 14:01

danhoeflinger force-pushed the dev/dhoeflin/unitialized_refactors branch from f02042d to e029ce4 Compare February 10, 2026 16:40

danhoeflinger force-pushed the dev/dhoeflin/remove_make_iter_mode branch from 267d03c to 1b39713 Compare February 10, 2026 17:07

danhoeflinger force-pushed the dev/dhoeflin/unitialized_refactors branch from e029ce4 to 46ff098 Compare February 20, 2026 16:41

danhoeflinger mentioned this pull request Feb 25, 2026

Access mode changes for transform_if #2556

Merged

danhoeflinger force-pushed the dev/dhoeflin/unitialized_refactors branch from 3060a9d to 90ff4fe Compare February 25, 2026 16:06

danhoeflinger added 2 commits February 25, 2026 15:23

refactor away redundant fill functor;

ec2d9db

fix access modes for uninitialized apis remove unnecessary pattern Signed-off-by: Dan Hoeflinger <dan.hoeflinger@intel.com>

fixing typo uninitialized_value_construct

d2e7ad7

Signed-off-by: Dan Hoeflinger <dan.hoeflinger@intel.com>

danhoeflinger added 12 commits February 25, 2026 15:23

revert formatting only changes

e2a89f1

Signed-off-by: Dan Hoeflinger <dan.hoeflinger@intel.com>

fixing rebase

9bd6615

Signed-off-by: Dan Hoeflinger <dan.hoeflinger@intel.com>

formatting

f0c541c

Signed-off-by: Dan Hoeflinger <dan.hoeflinger@intel.com>

formatting

e14d992

Signed-off-by: Dan Hoeflinger <dan.hoeflinger@intel.com>

formatting

5b845ec

Signed-off-by: Dan Hoeflinger <dan.hoeflinger@intel.com>

move from algorithm to memory

c899892

Signed-off-by: Dan Hoeflinger <dan.hoeflinger@intel.com>

reverting formatting only change

d94e5b9

formatting fixes

854a06a

Signed-off-by: Dan Hoeflinger <dan.hoeflinger@intel.com>

formatting

f1e0cd1

Signed-off-by: Dan Hoeflinger <dan.hoeflinger@intel.com>

adding memory_impl_hetero.h

4364736

Signed-off-by: Dan Hoeflinger <dan.hoeflinger@intel.com>

formatting, naming

9f4e504

fix header

3a67d40

Signed-off-by: Dan Hoeflinger <dan.hoeflinger@intel.com>

danhoeflinger force-pushed the dev/dhoeflin/unitialized_refactors branch from 6a2d1ce to 3a67d40 Compare February 25, 2026 20:23

danhoeflinger added 7 commits February 25, 2026 15:25

refactor sycl_iter resolver (remove make_iter_mode)

9b8191b

Signed-off-by: Dan Hoeflinger <dan.hoeflinger@intel.com>

fix trait (maintain good error msg)

0fd8e76

Signed-off-by: Dan Hoeflinger <dan.hoeflinger@intel.com>

remove unused trait, rework comments

f2b2e7d

Signed-off-by: Dan Hoeflinger <dan.hoeflinger@intel.com>

connecting no_init to accessors

b33e770

Signed-off-by: Dan Hoeflinger <dan.hoeflinger@intel.com>

formatting changes

ddec100

Signed-off-by: Dan Hoeflinger <dan.hoeflinger@intel.com>

removing unnecessary comment

c894054

Signed-off-by: Dan Hoeflinger <dan.hoeflinger@intel.com>

adding static assertion for read + no_init

7bfe401

Signed-off-by: Dan Hoeflinger <dan.hoeflinger@intel.com>

danhoeflinger force-pushed the dev/dhoeflin/remove_make_iter_mode branch from 1b39713 to 7bfe401 Compare February 25, 2026 20:26

danhoeflinger added 2 commits February 25, 2026 15:29

fix rebase mistake

1e123bd

adjusting the SFINAE to allow user-friendly static assertions to trigger

22627b8

Signed-off-by: Dan Hoeflinger <dan.hoeflinger@intel.com>

danhoeflinger force-pushed the dev/dhoeflin/unitialized_refactors branch from 0b61bcf to 0a56ec7 Compare March 2, 2026 16:05

Merge branch 'dev/dhoeflin/unitialized_refactors' into dev/dhoeflin/r…

394ea4a

…emove_make_iter_mode

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Remove `make_iter_mode` and refactor access mode resolution#2551

Remove `make_iter_mode` and refactor access mode resolution#2551
danhoeflinger wants to merge 24 commits intodev/dhoeflin/unitialized_refactorsfrom
dev/dhoeflin/remove_make_iter_mode

danhoeflinger commented Dec 29, 2025 •

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danhoeflinger commented Dec 29, 2025 •

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