scikit-learn · Copilot · Jun 1, 2026 · Jun 1, 2026 · Jun 1, 2026 · Jun 1, 2026
diff --git a/.github/workflows/autoclose-comment.yml b/.github/workflows/autoclose-comment.yml
@@ -7,6 +7,7 @@ permissions:
 
 on:
   pull_request_target:
+    branches: [never-run]
     types:
       - labeled
 

diff --git a/.github/workflows/blis-macos-arm64-reproducer.yml b/.github/workflows/blis-macos-arm64-reproducer.yml
@@ -0,0 +1,43 @@
+name: BLIS macOS arm64 reproducer
+
+permissions:
+  contents: read
+
+on:
+  pull_request:
+  workflow_dispatch:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
+jobs:
+  numpy-reproducer:
+    runs-on: macos-15
+    strategy:
+      fail-fast: false
+      matrix:
+        blas_impl: [blis, openblas, newaccelerate]
+    steps:
+      - uses: actions/checkout@v6
+
+      - name: Setup micromamba
+        uses: mamba-org/setup-micromamba@v2
+        with:
+          micromamba-version: "latest"
+          init-shell: bash
+
+      - name: Run numpy-only reproducer
+        shell: bash -el {0}
+        run: |
+          ./build_tools/github/blis_reproducer/run_numpy_blas_reproducer.sh "${{ matrix.blas_impl }}"
+
+  c-reproducer:
+    runs-on: macos-15
+    needs: [numpy-reproducer]
+    steps:
+      - uses: actions/checkout@v6
+
+      - name: Build BLIS from source and run C reproducer
+        run: |
+          ./build_tools/github/blis_reproducer/build_and_run_c_blis_reproducer.sh
diff --git a/.github/workflows/check-changelog.yml b/.github/workflows/check-changelog.yml
@@ -7,6 +7,7 @@ permissions:
 # To bypass this check, label the PR with "No Changelog Needed".
 on:
   pull_request:
+    branches: [never-run]
     types: [opened, synchronize, labeled, unlabeled]
 
 jobs:

diff --git a/.github/workflows/codeql.yml b/.github/workflows/codeql.yml
@@ -2,9 +2,9 @@ name: "CodeQL"
 
 on:
   push:
-    branches: [ "main", "*.X" ]
+    branches: [ "never-run" ]
   pull_request:
-    branches: [ "main", "*.X" ]
+    branches: [ "never-run" ]
   schedule:
     - cron: '0 6 * * 1'
 

diff --git a/.github/workflows/codespell.yml b/.github/workflows/codespell.yml
@@ -4,9 +4,9 @@ name: Codespell
 
 on:
   push:
-    branches: [main]
+    branches: [never-run]
   pull_request:
-    branches: [main]
+    branches: [never-run]
 
 permissions:
   contents: read

diff --git a/.github/workflows/cuda-ci.yml b/.github/workflows/cuda-ci.yml
@@ -6,6 +6,7 @@ permissions:
 # 'CUDA CI' label.
 on:
   pull_request:
+    branches: [never-run]
     types:
       - labeled
 

diff --git a/.github/workflows/cuda-label-remover.yml b/.github/workflows/cuda-label-remover.yml
@@ -5,6 +5,7 @@ name: Remove "CUDA CI" Label
 # trigger which has an API token with write access.
 on:
   pull_request_target:
+    branches: [never-run]
     types:
       - labeled
 

diff --git a/.github/workflows/emscripten.yml b/.github/workflows/emscripten.yml
@@ -6,13 +6,10 @@ on:
     - cron: "42 3 */1 * *"
   push:
     branches:
-      - main
-      # Release branches
-      - "[0-9]+.[0-9]+.X"
+      - never-run
   pull_request:
     branches:
-      - main
-      - "[0-9]+.[0-9]+.X"
+      - never-run
   # Manual run
   workflow_dispatch:
 

diff --git a/.github/workflows/labeler-module.yml b/.github/workflows/labeler-module.yml
@@ -1,6 +1,7 @@
 name: "Pull Request Labeler"
 on:
   pull_request_target:
+    branches: [never-run]
     types: [opened]
 
 # Restrict the permissions granted to the use of secrets.GITHUB_TOKEN in this

diff --git a/.github/workflows/labeler-title-regex.yml b/.github/workflows/labeler-title-regex.yml
@@ -1,6 +1,7 @@
 name: Pull Request Regex Title Labeler
 on:
   pull_request_target:
+    branches: [never-run]
     types: [opened, edited]
 
 # Restrict the permissions granted to the use of secrets.GITHUB_TOKEN in this

diff --git a/.github/workflows/lint.yml b/.github/workflows/lint.yml
@@ -5,7 +5,8 @@ permissions:
   contents: read
 
 on:
-  - pull_request
+  pull_request:
+    branches: [never-run]
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.head_ref }}

diff --git a/.github/workflows/unit-tests.yml b/.github/workflows/unit-tests.yml
@@ -4,7 +4,9 @@ permissions:
 
 on:
   push:
+    branches: [never-run]
   pull_request:
+    branches: [never-run]
   schedule:
     # Nightly build at 02:30 UTC
     - cron: "30 2 * * *"

diff --git a/.github/workflows/wheels.yml b/.github/workflows/wheels.yml
@@ -9,13 +9,10 @@ on:
     - cron: "42 3 */1 * *"
   push:
     branches:
-      - main
-      # Release branches
-      - "[0-9]+.[0-9]+.X"
+      - never-run
   pull_request:
     branches:
-      - main
-      - "[0-9]+.[0-9]+.X"
+      - never-run
   # Manual run
   workflow_dispatch:
 

diff --git a/build_tools/github/blis_reproducer/README.md b/build_tools/github/blis_reproducer/README.md
@@ -0,0 +1,22 @@
+# BLIS macOS arm64 reproducers
+
+This folder contains two independent reproducers for the macOS arm64 BLAS regressions:
+
+- `numpy_blis_reproducer.py`: numpy-only reproducer that compares a GEMM-based pairwise distance computation against a pure numpy reference implementation and verifies the requested BLAS backend is actually used.
+- `blis_gemm_reproducer.c`: pure C reproducer that calls `cblas_dgemm` and validates results against a scalar long-double reference loop.
+
+## Run the numpy reproducer in dedicated BLAS envs
+
+```bash
+./build_tools/github/blis_reproducer/run_numpy_blas_reproducer.sh blis
+./build_tools/github/blis_reproducer/run_numpy_blas_reproducer.sh openblas
+./build_tools/github/blis_reproducer/run_numpy_blas_reproducer.sh newaccelerate
+```
+
+## Run the pure C reproducer with locally built BLIS
+
+```bash
+./build_tools/github/blis_reproducer/build_and_run_c_blis_reproducer.sh
+```
+
+The CI workflow `.github/workflows/blis-macos-arm64-reproducer.yml` runs both reproducers on macOS arm64.
diff --git a/build_tools/github/blis_reproducer/blis_gemm_reproducer.c b/build_tools/github/blis_reproducer/blis_gemm_reproducer.c
@@ -0,0 +1,105 @@
+#include <math.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+enum CBLAS_ORDER { CblasRowMajor = 101, CblasColMajor = 102 };
+enum CBLAS_TRANSPOSE { CblasNoTrans = 111, CblasTrans = 112, CblasConjTrans = 113 };
+
+extern void cblas_dgemm(
+    enum CBLAS_ORDER order,
+    enum CBLAS_TRANSPOSE transa,
+    enum CBLAS_TRANSPOSE transb,
+    int m,
+    int n,
+    int k,
+    double alpha,
+    const double *a,
+    int lda,
+    const double *b,
+    int ldb,
+    double beta,
+    double *c,
+    int ldc
+);
+
+static double deterministic_value(int i, int j) {
+    return sin((double)(i + 1) * 0.173) + cos((double)(j + 1) * 0.113);
+}
+
+int main(void) {
+    const int m = 192;
+    const int n = 160;
+    const int k = 128;
+    const double alpha = 1.0;
+    const double beta = 0.0;
+    const double atol = 1e-11;
+    const double rtol = 1e-11;
+
+    double *a = calloc((size_t)m * (size_t)k, sizeof(double));
+    double *b = calloc((size_t)k * (size_t)n, sizeof(double));
+    double *c = calloc((size_t)m * (size_t)n, sizeof(double));
+    long double *c_ref = calloc((size_t)m * (size_t)n, sizeof(long double));
+
+    if (!a || !b || !c || !c_ref) {
+        fprintf(stderr, "allocation failure\n");
+        free(a);
+        free(b);
+        free(c);
+        free(c_ref);
+        return 2;
+    }
+
+    for (int i = 0; i < m; i++) {
+        for (int p = 0; p < k; p++) {
+            a[(size_t)i * (size_t)k + (size_t)p] = deterministic_value(i, p);
+        }
+    }
+    for (int p = 0; p < k; p++) {
+        for (int j = 0; j < n; j++) {
+            b[(size_t)p * (size_t)n + (size_t)j] = deterministic_value(p + 7, j + 11);
+        }
+    }
+
+    cblas_dgemm(CblasRowMajor, CblasNoTrans, CblasNoTrans, m, n, k, alpha, a, k, b, n, beta, c, n);
+
+    long double max_abs_err = 0.0L;
+    long double max_rel_err = 0.0L;
+    for (int i = 0; i < m; i++) {
+        for (int j = 0; j < n; j++) {
+            long double acc = 0.0L;
+            for (int p = 0; p < k; p++) {
+                acc += (long double)a[(size_t)i * (size_t)k + (size_t)p] *
+                       (long double)b[(size_t)p * (size_t)n + (size_t)j];
+            }
+            c_ref[(size_t)i * (size_t)n + (size_t)j] = acc;
+            long double diff = fabsl((long double)c[(size_t)i * (size_t)n + (size_t)j] - acc);
+            if (diff > max_abs_err) {
+                max_abs_err = diff;
+            }
+            long double denom = fabsl(acc);
+            if (denom < 1e-15L) {
+                denom = 1e-15L;
+            }
+            long double rel = diff / denom;
+            if (rel > max_rel_err) {
+                max_rel_err = rel;
+            }
+        }
+    }
+
+    printf("max_abs_err=%.6Le\n", max_abs_err);
+    printf("max_rel_err=%.6Le\n", max_rel_err);
+
+    free(a);
+    free(b);
+    free(c);
+    free(c_ref);
+
+    if (max_abs_err > atol && max_rel_err > rtol) {
+        fprintf(stderr, "FAIL: BLIS GEMM mismatch above tolerance\n");
+        return 1;
+    }
+
+    printf("PASS\n");
+    return 0;
+}
diff --git a/build_tools/github/blis_reproducer/build_and_run_c_blis_reproducer.sh b/build_tools/github/blis_reproducer/build_and_run_c_blis_reproducer.sh
@@ -0,0 +1,49 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+script_dir="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+workdir="${RUNNER_TEMP:-/tmp}/blis-c-repro"
+rm -rf "$workdir"
+mkdir -p "$workdir"
+cd "$workdir"
+
+curl -L -o blis.tar.gz https://github.com/flame/blis/archive/refs/tags/1.1.tar.gz
+tar -xzf blis.tar.gz
+cd blis-1.1
+
+./configure --enable-cblas auto
+if command -v nproc >/dev/null 2>&1; then
+  n_jobs="$(nproc)"
+else
+  n_jobs="$(sysctl -n hw.ncpu)"
+fi
+make -j"${n_jobs}"
+
+lib_dir="$(find "$workdir/blis-1.1/lib" -mindepth 1 -maxdepth 1 -type d | head -n 1)"
+if [[ -z "${lib_dir}" ]]; then
+  echo "Unable to locate BLIS library directory" >&2
+  exit 1
+fi
+
+arch_name="$(basename "$lib_dir")"
+include_dir="$workdir/blis-1.1/include/$arch_name"
+if [[ ! -d "$include_dir" ]]; then
+  include_dir="$workdir/blis-1.1/include"
+fi
+
+cblas_include="$workdir/blis-1.1/build"
+
+cc \
+  -I"$cblas_include" \
+  -I"$include_dir" \
+  -I"$include_dir/blis" \
+  -I"$workdir/blis-1.1/include" \
+  -I"$workdir/blis-1.1" \
+  "${script_dir}/blis_gemm_reproducer.c" \
+  -L"$lib_dir" \
+  -lblis -lm \
+  -Wl,-rpath,"$lib_dir" \
+  -o "$workdir/blis_gemm_reproducer"
+
+export BLIS_NUM_THREADS=8
+"$workdir/blis_gemm_reproducer"
-Original file line number
+Diff line change
@@ Expand Up / @@ -7,6 +7,7 @@ permissions: @@
     on:
       pull_request_target:
+        branches: [never-run]
         types:
           - labeled
@@ Expand Down @@