From 4d4208a53c1f831286da24bfec8ac00c8a0e987b Mon Sep 17 00:00:00 2001
From: co63oc <4617245+co63oc@users.noreply.github.com>
Date: Wed, 29 Jul 2026 17:15:43 +0800
Subject: [PATCH 1/2] [SWE-Paddle] Add task PaddlePaddle__Paddle-74212

---
 .../PaddlePaddle__Paddle-74212/README.md      | 51 ++++++++++++++++
 .../environment/README.md                     | 51 ++++++++++++++++
 .../PaddlePaddle__Paddle-74212/instruction.md | 53 +++++++++++++++++
 .../PaddlePaddle__Paddle-74212/proposal.md    | 58 +++++++++++++++++++
 .../solution/code.patch                       | 24 ++++++++
 .../tests/test.patch                          | 53 +++++++++++++++++
 .../PaddlePaddle__Paddle-74212/tests/test.sh  |  4 ++
 7 files changed, 294 insertions(+)
 create mode 100644 swe-paddle/tasks/PaddlePaddle__Paddle-74212/README.md
 create mode 100644 swe-paddle/tasks/PaddlePaddle__Paddle-74212/environment/README.md
 create mode 100644 swe-paddle/tasks/PaddlePaddle__Paddle-74212/instruction.md
 create mode 100644 swe-paddle/tasks/PaddlePaddle__Paddle-74212/proposal.md
 create mode 100644 swe-paddle/tasks/PaddlePaddle__Paddle-74212/solution/code.patch
 create mode 100644 swe-paddle/tasks/PaddlePaddle__Paddle-74212/tests/test.patch
 create mode 100755 swe-paddle/tasks/PaddlePaddle__Paddle-74212/tests/test.sh

diff --git a/swe-paddle/tasks/PaddlePaddle__Paddle-74212/README.md b/swe-paddle/tasks/PaddlePaddle__Paddle-74212/README.md
new file mode 100644
index 000000000..54798d113
--- /dev/null
+++ b/swe-paddle/tasks/PaddlePaddle__Paddle-74212/README.md
@@ -0,0 +1,51 @@
+# PaddlePaddle__Paddle-74212
+
+This directory converts Paddle PR #74212 into a SWE-Paddle community task candidate.
+
+## Source
+
+| Field | Value |
+| --- | --- |
+| Repo | `PaddlePaddle/Paddle` |
+| PR | [74212](https://github.com/PaddlePaddle/Paddle/pull/74212) |
+| PR title | `[0-size Tensor Job2 No.51] Add 0-size Tensor support for paddle.multiplex` |
+| Base commit | `0f3860d981460b0b788aa50836a215f59c90e32a` |
+| Gold commit | `3e59330aa066d997e24ff6c5c74c19b250fae43d` |
+| Merged at | `2025-07-28` |
+| Task type | `bug_fix` |
+| Resource | CPU |
+| Scope | C++ Operator Kernel |
+
+## Summary
+
+Fix `paddle.multiplex` to correctly handle 0-size tensors in CPU/GPU kernels by adding early-return logic when output numel is 0.
+
+## Why This Is A Good SWE-Paddle Candidate
+
+- It is derived from a merged Paddle bug-fix PR rather than a synthetic issue.
+- The target behavior is isolated to the C++ operator kernel level and requires rebuilding Paddle from source.
+- The failure is deterministic: the base revision fails when processing 0-size tensors due to PADDLE_ENFORCE_GT checks on input numel.
+- The task has clear regression coverage for existing non-zero-size behavior.
+- The task runs on CPU and does not require distributed execution, external services, or additional datasets.
+
+## Files
+
+- `proposal.md`: candidate proposal for maintainer triage.
+- `instruction.md`: self-contained problem statement for the coding agent.
+- `solution/code.patch`: gold implementation patch (C++ kernel changes).
+- `tests/test.patch`: tests exposing the target behavior.
+- `tests/test.sh`: minimal target test command.
+- `environment/README.md`: environment and reproduction notes.
+
+## Verification
+
+```bash
+bash tests/test.sh
+```
+
+Expected behavior:
+
+| Revision state | Existing behavior (P2P) | multiplex F2P |
+| --- | ---: | ---: |
+| Base + `tests/test.patch` | PASS | FAIL |
+| Base + `tests/test.patch` + `solution/code.patch` | PASS | PASS |
diff --git a/swe-paddle/tasks/PaddlePaddle__Paddle-74212/environment/README.md b/swe-paddle/tasks/PaddlePaddle__Paddle-74212/environment/README.md
new file mode 100644
index 000000000..bb6d7b394
--- /dev/null
+++ b/swe-paddle/tasks/PaddlePaddle__Paddle-74212/environment/README.md
@@ -0,0 +1,51 @@
+# Environment Notes
+
+## Expected Environment
+
+- Repository: `PaddlePaddle/Paddle`
+- Base commit: `0f3860d981460b0b788aa50836a215f59c90e32a`
+- Gold commit: `3e59330aa066d997e24ff6c5c74c19b250fae43d`
+- Resource: CPU
+- GPU required: no
+- Patch type: C++ kernel (CPU/GPU backends)
+- Python dependencies: PaddlePaddle (source build), NumPy
+
+The verifier should execute against the Paddle source revision represented by the selected patch state. A source build is required since the patch modifies C++ kernel code.
+
+## Build Instructions
+
+1. Check out `PaddlePaddle/Paddle` at the base commit.
+2. Apply `tests/test.patch`.
+3. Build Paddle from source (CPU-only build is sufficient):
+   ```bash
+   mkdir build && cd build
+   cmake .. -DWITH_GPU=OFF -DWITH_TESTING=ON -DCMAKE_BUILD_TYPE=Release
+   make -j$(nproc)
+   ```
+4. Install the built Paddle package.
+
+## Run Order
+
+1. Check out `PaddlePaddle/Paddle` at the base commit.
+2. Build and install Paddle from source.
+3. Apply `tests/test.patch`.
+4. Run the P2P tests; existing non-zero-size behavior should pass.
+5. Run the 0-size tensor tests; the target case should fail before the fix.
+6. Apply `solution/code.patch`.
+7. Rebuild Paddle from source.
+8. Run `bash tests/test.sh`; all target tests should pass.
+
+## Minimal Test Command
+
+```bash
+bash tests/test.sh
+```
+
+## Expected Matrix
+
+| Revision state | P2P | multiplex F2P |
+| --- | ---: | ---: |
+| Base + test patch | PASS | FAIL |
+| Base + test patch + solution patch | PASS | PASS |
+
+No GPU, distributed runtime, external service, or additional dataset is required.
diff --git a/swe-paddle/tasks/PaddlePaddle__Paddle-74212/instruction.md b/swe-paddle/tasks/PaddlePaddle__Paddle-74212/instruction.md
new file mode 100644
index 000000000..6f47bf6f5
--- /dev/null
+++ b/swe-paddle/tasks/PaddlePaddle__Paddle-74212/instruction.md
@@ -0,0 +1,53 @@
+# 修复 `paddle.multiplex` 对 0-size Tensor 的处理
+
+## 详细描述
+
+当 `paddle.multiplex(inputs, index)` 的所有输入 `inputs` 均为 0-size Tensor（即 `out.numel() == 0`）时，当前 CPU/GPU kernel 实现会直接进入后续计算逻辑，导致 kernel 内部的 `PADDLE_ENFORCE_GT(ins[i]->numel(), 0, ...)` 检查失败并报错。
+
+典型表现包括：
+
+- kernel 抛出 `PreconditionNotMet` 错误，提示输入 numel 必须大于 0
+- 0-size Tensor 输入无法通过 multiplex 算子
+
+例如：
+
+```python
+import numpy as np
+import paddle
+
+paddle.disable_static()
+rows = 4
+index = np.array([0, 2, 2, 3]).astype('int32')
+index = np.reshape(index, (rows, 1))
+ins1 = np.random.random((rows, 0)).astype('float64')
+ins2 = np.random.random((rows, 0)).astype('float64')
+ins3 = np.random.random((rows, 0)).astype('float64')
+ins4 = np.random.random((rows, 0)).astype('float64')
+
+x1 = paddle.to_tensor(ins1)
+x2 = paddle.to_tensor(ins2)
+x3 = paddle.to_tensor(ins3)
+x4 = paddle.to_tensor(ins4)
+ids = paddle.to_tensor(index)
+
+out = paddle.multiplex([x1, x2, x3, x4], ids)
+```
+
+上述调用中所有输入的 shape 为 `[4, 0]`，`out.numel() == 0`。按照 API semantics，当所有输入均为 0-size 时，不存在需要多路选择的数据，因此该调用应正常完成并返回正确 shape 的空 Tensor。
+
+当前 C++ kernel 层在进入后续计算之前，没有对 0-size 输出进行显式的早期返回处理。当 `out->numel() == 0` 时，应在完成 output tensor 的 Alloc 之后，直接返回，跳过后续的 numel 检查和数据拷贝逻辑。
+
+## 验收说明
+
+- 当所有输入均为 0-size Tensor 时，`paddle.multiplex` kernel 应正常完成，返回正确 shape 的空 Tensor
+- 输出的 shape 应与输入一致（除第一维由 index 决定外）
+- 非 0-size Tensor 输入下的 multiplex 行为不得退化
+- 梯度计算也应正常工作（0-size Tensor 的梯度也为空 Tensor）
+
+## 技术要求
+
+- 熟悉 C++ 和 Paddle PHI kernel 开发
+- 了解 Tensor shape、0-size Tensor 和 kernel 执行路径
+- 了解 multiplex 算子的输入输出语义
+- 了解 Paddle CPU/GPU kernel 的多 backend 实现模式
+- 需要从源码编译 Paddle 以验证修改
diff --git a/swe-paddle/tasks/PaddlePaddle__Paddle-74212/proposal.md b/swe-paddle/tasks/PaddlePaddle__Paddle-74212/proposal.md
new file mode 100644
index 000000000..ef1b9db09
--- /dev/null
+++ b/swe-paddle/tasks/PaddlePaddle__Paddle-74212/proposal.md
@@ -0,0 +1,58 @@
+# SWE-Paddle Task Proposal: PaddlePaddle__Paddle-74212
+
+## 1. 来源信息
+
+- Instance ID: `PaddlePaddle__Paddle-74212`
+- PR 链接: https://github.com/PaddlePaddle/Paddle/pull/74212
+- PR 标题: `[0-size Tensor Job2 No.51] Add 0-size Tensor support for paddle.multiplex`
+- Base commit: `0f3860d981460b0b788aa50836a215f59c90e32a`
+- Gold commit: `3e59330aa066d997e24ff6c5c74c19b250fae43d`
+- Merged at: 2025-07-28
+- 你的身份: contributor
+
+## 2. 问题一句话
+
+`paddle.multiplex` 在输入为 0-size Tensor 时，kernel 会因 PADDLE_ENFORCE_GT 检查每个输入 numel > 0 而报错，需要在 kernel 入口添加 0-size 早期返回逻辑。
+
+## 3. 为什么适合作为 SWE-Paddle 样本
+
+- **真实性**: 来自 Paddle「0-size Tensor 机制建设」系列任务，是真实研发需求。
+- **代表性**: 覆盖 C++ kernel 层面的 0-size Tensor 边界处理，涉及 CPU/GPU 双端 kernel，需要在 kernel 入口添加 `out->numel() == 0` 的早期返回。
+- **边界清楚**: 目标仅限所有输入均为 0-size 时的 kernel 早期返回；正向非零尺寸输入不应受影响。
+- **非平凡性**: 修复需要在 CPU/GPU 两个 backend 的 kernel 中分别添加 `if (out->numel() == 0) return;`，涉及对 kernel 执行流程的理解和 0-size Tensor 语义的把握。
+- **回归护栏明确**: 目标 F2P 可覆盖 0-size Tensor 输入的 `multiplex` 算子测试；同文件中已有的 `TestMultiplexOp` 等标准测试用例可作为 P2P 护栏。
+
+## 4. 任务类型和标签
+
+- 任务类型: `bug_fix`
+- 执行后端: `cpu`
+- 设备范围: `cpu_only`
+- 模块标签: `[operator_kernel, multiplex, 0-size_tensor, cpu_kernel, gpu_kernel]`
+
+## 5. 验证思路
+
+- 目标测试命令: `bash tests/test.sh`
+- 目标测试文件:
+  - `test/legacy_test/test_multiplex_op.py`（`TestMultiplexOp_ZeroSize`）
+- P2P 候选: 同文件中已有的 `TestMultiplexOp`、`TestMultiplexODygrap` 等标准 multiplex 算子测试用例。
+- 修复前预期: `base_commit` + `tests/test.patch` 后，0-size Tensor 输入的 `multiplex` 算子测试失败（kernel 内部 PADDLE_ENFORCE_GT 报错）。
+- 修复后预期: 继续应用 `solution/code.patch` 并重新编译后，0-size Tensor 输入正常返回空 Tensor，P2P 存量测试仍然通过。
+
+## 6. 环境与资源
+
+- 是否能提供 Docker: 无
+- Dockerfile 或镜像地址: 暂无
+- Paddle 来源: `PaddlePaddle/Paddle` source checkout at `base_commit`，需要源码编译。
+- OS / Python / CUDA / cuDNN / 其他关键依赖: Linux CPU + Python + numpy；编译需要 CMake、GCC；不要求 CUDA/cuDNN（CPU 编译即可验证）。
+- 硬件: CPU 即可（编译和测试均不需要 GPU）。
+- patch 类型: 含 C++ kernel 修改（CPU/GPU 双端），需要重新编译 Paddle。
+- 最小测试命令: `bash tests/test.sh`
+- 是否有 oracle 日志: 无
+
+## 7. 风险自查
+
+- 泄露风险: 正式 `instruction.md` 只描述「multiplex 对 0-size Tensor 输入的行为异常」，不指出具体 `out->numel() == 0` 分支逻辑或具体代码位置。
+- 环境风险: 中。任务涉及 C++ kernel 修改，需要源码编译 Paddle，编译时间较长。
+- flaky 风险: 低。测试使用固定的 0-size Tensor 构造，不依赖随机数差异或多设备同步。
+- 拆分风险: 低。该 PR 目标集中在 `multiplex_kernel` 的 CPU/GPU 双端 0-size 早期返回，测试明确指向 `TestMultiplexOp_ZeroSize`，适合作为一个独立样本。
+- 其他不确定点: 完整任务包阶段应确认新增 F2P（`TestMultiplexOp_ZeroSize`）在 `base_commit` 编译后确实失败。
diff --git a/swe-paddle/tasks/PaddlePaddle__Paddle-74212/solution/code.patch b/swe-paddle/tasks/PaddlePaddle__Paddle-74212/solution/code.patch
new file mode 100644
index 000000000..4d011cf43
--- /dev/null
+++ b/swe-paddle/tasks/PaddlePaddle__Paddle-74212/solution/code.patch
@@ -0,0 +1,24 @@
+diff --git a/paddle/phi/kernels/cpu/multiplex_kernel.cc b/paddle/phi/kernels/cpu/multiplex_kernel.cc
+index 6e38a255a1..f91879dd45 100644
+--- a/paddle/phi/kernels/cpu/multiplex_kernel.cc
++++ b/paddle/phi/kernels/cpu/multiplex_kernel.cc
+@@ -26,6 +26,7 @@ void MultiplexKernel(const Context& dev_ctx,
+                      const DenseTensor& ids,
+                      DenseTensor* out) {
+   dev_ctx.template Alloc<T>(out);
++  if (out->numel() == 0) return;
+   for (size_t i = 0; i < ins.size(); ++i) {
+     PADDLE_ENFORCE_GT(
+         ins[i]->numel(),
+diff --git a/paddle/phi/kernels/gpu/multiplex_kernel.cu b/paddle/phi/kernels/gpu/multiplex_kernel.cu
+index 33fa3a74c5..b66cc4836b 100644
+--- a/paddle/phi/kernels/gpu/multiplex_kernel.cu
++++ b/paddle/phi/kernels/gpu/multiplex_kernel.cu
+@@ -27,6 +27,7 @@ void MultiplexKernel(const Context& dev_ctx,
+                      const DenseTensor& ids,
+                      DenseTensor* out) {
+   dev_ctx.template Alloc<T>(out);
++  if (out->numel() == 0) return;
+   for (size_t i = 0; i < ins.size(); ++i) {
+     PADDLE_ENFORCE_GT(
+         ins[i]->numel(),
diff --git a/swe-paddle/tasks/PaddlePaddle__Paddle-74212/tests/test.patch b/swe-paddle/tasks/PaddlePaddle__Paddle-74212/tests/test.patch
new file mode 100644
index 000000000..6246e8f44
--- /dev/null
+++ b/swe-paddle/tasks/PaddlePaddle__Paddle-74212/tests/test.patch
@@ -0,0 +1,53 @@
+diff --git a/test/legacy_test/test_multiplex_op.py b/test/legacy_test/test_multiplex_op.py
+index 67d3b0bbf7..0c69efeed9 100644
+--- a/test/legacy_test/test_multiplex_op.py
++++ b/test/legacy_test/test_multiplex_op.py
+@@ -97,6 +97,7 @@ class TestMultiplexOp_complex128(TestMultiplexOp):
+ class TestMultiplexOpError(unittest.TestCase):
+ 
+     def test_errors(self):
++        paddle.enable_static()
+         with base.program_guard(base.Program(), base.Program()):
+             x1 = paddle.static.data(name='x1', shape=[None, 2], dtype='int64')
+             x2 = paddle.static.data(name='x2', shape=[None, 2], dtype='int64')
+@@ -198,5 +199,40 @@ class TestMultiplexODygrap_complex128(TestMultiplexODygrap):
+         self.dtype = np.complex128
+ 
+ 
++class TestMultiplexOp_ZeroSize(OpTest):
++    def setUp(self):
++        self.op_type = "multiplex"
++        self.init_dtype()
++        self.python_api = paddle.tensor.multiplex
++        rows = 4
++        index = np.array([0, 2, 2, 3]).astype('int32')
++        np.random.shuffle(index)
++        index = np.reshape(index, (rows, 1))
++        ins1 = np.random.random((rows, 0)).astype(self.dtype)
++        ins2 = np.random.random((rows, 0)).astype(self.dtype)
++        ins3 = np.random.random((rows, 0)).astype(self.dtype)
++        ins4 = np.random.random((rows, 0)).astype(self.dtype)
++        self.inputs = {
++            'Ids': index,
++            'X': [('x1', ins1), ('x2', ins2), ('x3', ins3), ('x4', ins4)],
++        }
++        # multiplex output
++        output = np.zeros_like(ins1)
++        for i in range(0, rows):
++            k = index[i][0]
++            if self.inputs['X'][k][1][i].size != 0:
++                output[i] = self.inputs['X'][k][1][i]
++        self.outputs = {'Out': output}
++
++    def init_dtype(self):
++        self.dtype = 'float64'
++
++    def test_check_output(self):
++        self.check_output(check_pir=True)
++
++    def test_check_grad(self):
++        self.check_grad(['x1', 'x2', 'x3', 'x4'], 'Out', check_pir=True)
++
++
+ if __name__ == '__main__':
+     unittest.main()
diff --git a/swe-paddle/tasks/PaddlePaddle__Paddle-74212/tests/test.sh b/swe-paddle/tasks/PaddlePaddle__Paddle-74212/tests/test.sh
new file mode 100755
index 000000000..d5b13175f
--- /dev/null
+++ b/swe-paddle/tasks/PaddlePaddle__Paddle-74212/tests/test.sh
@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+python -m pytest test/legacy_test/test_multiplex_op.py::TestMultiplexOp_ZeroSize -q

From 38c452a895539e24c2acecd928faa122f79a11b3 Mon Sep 17 00:00:00 2001
From: co63oc <4617245+co63oc@users.noreply.github.com>
Date: Wed, 29 Jul 2026 17:28:20 +0800
Subject: [PATCH 2/2] Add P2P tests for TestMultiplexOp

---
 swe-paddle/tasks/PaddlePaddle__Paddle-74212/tests/test.sh | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/swe-paddle/tasks/PaddlePaddle__Paddle-74212/tests/test.sh b/swe-paddle/tasks/PaddlePaddle__Paddle-74212/tests/test.sh
index d5b13175f..9fb891241 100755
--- a/swe-paddle/tasks/PaddlePaddle__Paddle-74212/tests/test.sh
+++ b/swe-paddle/tasks/PaddlePaddle__Paddle-74212/tests/test.sh
@@ -1,4 +1,8 @@
 #!/usr/bin/env bash
 set -euo pipefail
 
+# P2P tests (pass-to-pass)
+python -m pytest test/legacy_test/test_multiplex_op.py::TestMultiplexOp -q
+
+# F2P tests (fail-to-pass)
 python -m pytest test/legacy_test/test_multiplex_op.py::TestMultiplexOp_ZeroSize -q