Try setting explicit openmp implementations.

abs.yaml

@@ -1,3 +1,6 @@
 # Increase timeout for CUDA builds which compile for multiple GPU architectures
 # Default is 7200 seconds (2 hours), which is insufficient for Windows CUDA builds
 task_timeout: 14400  # 4 hours
+
+channels:
+  - build

recipe/build-lib.sh

@@ -6,12 +6,28 @@ cd ${SRC_DIR}
 function version2int { echo "$@" | awk -F. '{ printf("%d%02d\n", $1, $2); }'; }
 
 declare -a EXTRA_CMAKE_ARGS
-# Cross builds (linux-aarch64, linux-ppc64le, linux-s390x, osx-arm64) link
-# against OpenBLAS instead of MKL. Force FindBLAS to use OpenBLAS so it does
-# not attempt to run detection binaries on the build host (which fails when
-# cross compiling). Also hand CMake the actual library path so it does not try
-# to execute detection binaries under emulation.
-if [[ "${target_platform}" == linux-aarch64 || "${target_platform}" == osx-arm64 ]]; then
+if [[ "${target_platform}" == osx-* ]]; then
+    EXTRA_CMAKE_ARGS+=(
+        -DOpenMP_CXX_FLAGS="-Xpreprocessor -fopenmp"
+        -DOpenMP_CXX_LIB_NAMES=omp
+        -DOpenMP_omp_LIBRARY="$PREFIX/lib/libomp.dylib"
+    )
+elif [[ "${target_platform}" == linux-* && "${blas_impl}" == "mkl" ]]; then
+    OPENMP_CXX_FLAG="-fopenmp"
+    if [[ "${CXX:-}" == *icpx* || "${CXX:-}" == *icpc* || "${CXX:-}" == *icc* ]]; then
+        OPENMP_CXX_FLAG="-qopenmp"
+    fi
+    EXTRA_CMAKE_ARGS+=(
+        -DOpenMP_CXX_FLAGS="${OPENMP_CXX_FLAG}"
+        -DOpenMP_CXX_LIB_NAMES=iomp5
+        -DOpenMP_iomp5_LIBRARY="$PREFIX/lib/libiomp5.so"
+    )
+fi
+
+# Force FindBLAS to use the selected OpenBLAS variant instead of probing other
+# BLAS implementations. Hand CMake the actual library path so cross builds do
+# not try to execute detection binaries under emulation.
+if [[ "${blas_impl}" == "openblas" ]]; then
     EXTRA_CMAKE_ARGS+=(-DBLA_VENDOR=OpenBLAS)
     if [[ "${target_platform}" == osx-arm64 ]]; then
         EXTRA_CMAKE_ARGS+=(

recipe/build-pkg.sh

@@ -10,60 +10,50 @@ else
     FAISS_ENABLE_GPU="OFF"
 fi
 
-# Build vanilla version (no avx2), see build-lib.sh
-if [[ "${target_platform}" == "osx-64" ]]; then
-  cmake -G Ninja \
-      ${CMAKE_ARGS} \
-      -Dfaiss_ROOT=_libfaiss_generic_stage/ \
-      -DFAISS_ENABLE_GPU=${FAISS_ENABLE_GPU} \
-      -DOpenMP_CXX_FLAGS=-fopenmp=libiomp5 \
-      -DOpenMP_CXX_LIB_NAMES=libiomp5 \
-      -DOpenMP_libiomp5_LIBRARY=$PREFIX/lib/libiomp5.dylib \
-      -DCMAKE_BUILD_TYPE=Release \
-      -DPython_EXECUTABLE="${PYTHON}" \
-      -B _build_python_generic \
-      faiss/python
-  cmake --build _build_python_generic --target swigfaiss -j $CPU_COUNT
-else
-  cmake -G Ninja \
-      ${CMAKE_ARGS} \
-      -Dfaiss_ROOT=_libfaiss_generic_stage/ \
-      -DFAISS_ENABLE_GPU=${FAISS_ENABLE_GPU} \
-      -DCMAKE_BUILD_TYPE=Release \
-      -DPython_EXECUTABLE="${PYTHON}" \
-      -B _build_python_generic \
-      faiss/python
-  cmake --build _build_python_generic --target swigfaiss -j $CPU_COUNT
+declare -a OPENMP_CMAKE_ARGS
+if [[ "${target_platform}" == osx-* ]]; then
+    OPENMP_CMAKE_ARGS+=(
+        -DOpenMP_CXX_FLAGS="-Xpreprocessor -fopenmp"
+        -DOpenMP_CXX_LIB_NAMES=omp
+        -DOpenMP_omp_LIBRARY="$PREFIX/lib/libomp.dylib"
+    )
+elif [[ "${target_platform}" == linux-* && "${blas_impl}" == "mkl" ]]; then
+    OPENMP_CXX_FLAG="-fopenmp"
+    if [[ "${CXX:-}" == *icpx* || "${CXX:-}" == *icpc* || "${CXX:-}" == *icc* ]]; then
+        OPENMP_CXX_FLAG="-qopenmp"
+    fi
+    OPENMP_CMAKE_ARGS+=(
+        -DOpenMP_CXX_FLAGS="${OPENMP_CXX_FLAG}"
+        -DOpenMP_CXX_LIB_NAMES=iomp5
+        -DOpenMP_iomp5_LIBRARY="$PREFIX/lib/libiomp5.so"
+    )
 fi
 
+# Build vanilla version (no avx2), see build-lib.sh
+cmake -G Ninja \
+    ${CMAKE_ARGS} \
+    ${OPENMP_CMAKE_ARGS+"${OPENMP_CMAKE_ARGS[@]}"} \
+    -Dfaiss_ROOT=_libfaiss_generic_stage/ \
+    -DFAISS_ENABLE_GPU=${FAISS_ENABLE_GPU} \
+    -DCMAKE_BUILD_TYPE=Release \
+    -DPython_EXECUTABLE="${PYTHON}" \
+    -B _build_python_generic \
+    faiss/python
+cmake --build _build_python_generic --target swigfaiss -j $CPU_COUNT
+
 # Build version with avx2 support, see build-lib.sh
 if [[ "${target_platform}" == *-64 ]]; then
-    if [[ "${target_platform}" == "osx-64" ]]; then
-        cmake -G Ninja \
-            ${CMAKE_ARGS} \
-            -Dfaiss_ROOT=_libfaiss_avx2_stage/ \
-            -DOpenMP_CXX_FLAGS=-fopenmp=libiomp5 \
-            -DOpenMP_CXX_LIB_NAMES=libiomp5 \
-            -DOpenMP_libiomp5_LIBRARY=$PREFIX/lib/libiomp5.dylib \
-            -DFAISS_OPT_LEVEL=avx2 \
-            -DFAISS_ENABLE_GPU=${FAISS_ENABLE_GPU} \
-            -DCMAKE_BUILD_TYPE=Release \
-            -DPython_EXECUTABLE="${PYTHON}" \
-            -B _build_python_avx2 \
-            faiss/python
-        cmake --build _build_python_avx2 --target swigfaiss_avx2 -j $CPU_COUNT
-    else
-        cmake -G Ninja \
-            ${CMAKE_ARGS} \
-            -Dfaiss_ROOT=_libfaiss_avx2_stage/ \
-            -DFAISS_OPT_LEVEL=avx2 \
-            -DFAISS_ENABLE_GPU=${FAISS_ENABLE_GPU} \
-            -DCMAKE_BUILD_TYPE=Release \
-            -DPython_EXECUTABLE="${PYTHON}" \
-            -B _build_python_avx2 \
-            faiss/python
-        cmake --build _build_python_avx2 --target swigfaiss_avx2 -j $CPU_COUNT
-    fi
+    cmake -G Ninja \
+        ${CMAKE_ARGS} \
+        ${OPENMP_CMAKE_ARGS+"${OPENMP_CMAKE_ARGS[@]}"} \
+        -Dfaiss_ROOT=_libfaiss_avx2_stage/ \
+        -DFAISS_OPT_LEVEL=avx2 \
+        -DFAISS_ENABLE_GPU=${FAISS_ENABLE_GPU} \
+        -DCMAKE_BUILD_TYPE=Release \
+        -DPython_EXECUTABLE="${PYTHON}" \
+        -B _build_python_avx2 \
+        faiss/python
+    cmake --build _build_python_avx2 --target swigfaiss_avx2 -j $CPU_COUNT
 
     # copy generated swig module with avx2-support to specifically named file, cf.
     # https://github.com/facebookresearch/faiss/blob/v1.7.1/faiss/python/setup.py#L37-L40

recipe/conda_build_config.yaml

@@ -1,39 +1,5 @@
-# faiss v1.14.1 requires C++20 on MSVC (template lambdas in simd_dispatch.h).
-# vs2019 doesn't support C++20 template lambdas; vs2022 required for all variants.
-c_compiler:                        # [win]
-  - vs2022                         # [win]
-  - vs2022                         # [win]
-  - vs2022                         # [win]
-cxx_compiler:                      # [win]
-  - vs2022                         # [win]
-  - vs2022                         # [win]
-  - vs2022                         # [win]
 
 cuda_compiler_version:
   - None                                                                       # CPU variant - always built
   - "12.9"             # [win or linux]
-  - "13.1"             # [win or linux]
-
-# Python 3.13 builds currently fail on macOS (upstream SWIG bindings not ready).
-# Upstream issue: https://github.com/facebookresearch/faiss/issues/3985
-python:
-  - 3.10
-  - "3.11"
-  - "3.12"
-  - "3.13"           # [not osx]
-
-numpy:
-  - 2.1
-  - 2.1
-  - 2.1
-  - 2.1              # [not osx]
-
-blas_impl:
-  - mkl              # [not (aarch64 or arm64)]
-  - openblas         # [aarch64 or arm64]
-
-zip_keys:                          # [win]
-  -                                # [win]
-    - cuda_compiler_version        # [win]
-    - c_compiler                   # [win]
-    - cxx_compiler                 # [win]
+  - "13.0"             # [win or linux]