Use g++-14 and fix AVX-512 auto-detection in containers

- compare-tfhers.def, compare-tfhers.yml: install g++-14 and pass
  -DCMAKE_CXX_COMPILER=g++-14 / -DCMAKE_C_COMPILER=gcc-14 to cmake
- CMakeLists.txt: replace check_cxx_source_runs with /proc/cpuinfo as
  the primary AVX-512 detection path; check_cxx_source_runs fails in
  container build environments (Apptainer %post, Docker RUN) because
  the sandbox blocks executing compiled test binaries during cmake
  configuration. /proc/cpuinfo is always visible through the host
  kernel in Apptainer/Docker and requires no binary execution.
  Falls back to check_cxx_source_compiles for non-Linux systems.
- README.md: update tfhe-rs comparison results (g++-14 + AVX-512 now
  active in container: TFHEpp 6.17 ms, tfhe-rs 5.83 ms)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: nindanaoto

.github/workflows/compare-tfhers.yml

@@ -18,7 +18,7 @@ jobs:
         run: |
           apt-get update
           DEBIAN_FRONTEND=noninteractive apt-get install -y \
-            build-essential g++ libomp-dev cmake ninja-build git \
+            build-essential g++-14 libomp-dev cmake ninja-build git \
             curl wget ca-certificates
 
       # ── Rust toolchain (rustup) ───────────────────────────────────────────
@@ -47,6 +47,8 @@ jobs:
         run: |
           cmake . -B build -G Ninja \
             -DCMAKE_BUILD_TYPE=Release \
+            -DCMAKE_CXX_COMPILER=g++-14 \
+            -DCMAKE_C_COMPILER=gcc-14 \
             -DUSE_TFHE_RS=ON \
             -DENABLE_TEST=ON
           cmake --build build --target pbs_tfhers

CMakeLists.txt

@@ -31,33 +31,40 @@ option(USE_KEY_BUNDLE "Use key bundle algorithm" OFF)
 option(USE_BLAKE3 "Use blake3 as CSPRNG" ON)
 option(USE_RANDEN "Use randen as CSPRNG" OFF)
 
-# Detect AVX-512 support at configure time
+# Detect AVX-512 support at configure time.
+# Strategy (in priority order):
+#   1. /proc/cpuinfo — works in containers (Apptainer/Docker) without executing
+#      a compiled binary, because the host kernel's /proc is always visible.
+#   2. check_cxx_source_compiles with -mavx512f — compile-only check for
+#      non-Linux or cross-compile environments (macOS, Windows, etc.).
+# check_cxx_source_runs is intentionally avoided: it fails in container build
+# environments (Apptainer %post, Docker RUN) where sandbox restrictions prevent
+# executing compiled binaries during cmake configuration.
 if(NOT DEFINED AVX512_SUPPORTED)
+  set(AVX512_SUPPORTED FALSE)
   if(CMAKE_SYSTEM_PROCESSOR MATCHES "x86_64|AMD64|amd64")
-    include(CheckCXXSourceRuns)
-    set(CMAKE_REQUIRED_FLAGS "-mavx512f")
-    check_cxx_source_runs("
-      #include <immintrin.h>
-      int main(int argc, char**) {
-        double data[8] __attribute__((aligned(64)));
-        for (int i = 0; i < 8; i++) data[i] = static_cast<double>(argc + i);
-        __m512d a = _mm512_load_pd(data);
-        __m512d b = _mm512_add_pd(a, a);
-        _mm512_store_pd(data, b);
-        return static_cast<int>(data[0]) - 2 * argc;
-      }
-    " AVX512_SUPPORTED)
-    unset(CMAKE_REQUIRED_FLAGS)
-  else()
-    set(AVX512_SUPPORTED FALSE)
-  endif()
-endif()
-
-if(AVX512_SUPPORTED AND EXISTS "/proc/cpuinfo")
-  file(READ "/proc/cpuinfo" TFHEPP_CPUINFO)
-  if(NOT TFHEPP_CPUINFO MATCHES "avx512f")
-    message(STATUS "AVX-512 flags not found in /proc/cpuinfo; disabling AVX-512")
-    set(AVX512_SUPPORTED FALSE)
+    if(EXISTS "/proc/cpuinfo")
+      file(READ "/proc/cpuinfo" TFHEPP_CPUINFO)
+      if(TFHEPP_CPUINFO MATCHES "avx512f")
+        set(AVX512_SUPPORTED TRUE)
+      endif()
+    endif()
+    if(NOT AVX512_SUPPORTED)
+      include(CheckCXXSourceCompiles)
+      set(CMAKE_REQUIRED_FLAGS "-mavx512f")
+      check_cxx_source_compiles("
+        #include <immintrin.h>
+        int main() {
+          __m512d a = _mm512_setzero_pd();
+          (void)a;
+          return 0;
+        }
+      " AVX512_COMPILE_SUPPORTED)
+      unset(CMAKE_REQUIRED_FLAGS)
+      if(AVX512_COMPILE_SUPPORTED)
+        set(AVX512_SUPPORTED TRUE)
+      endif()
+    endif()
   endif()
 endif()
 

README.md

@@ -159,8 +159,8 @@ Measured with `apptainer run compare-tfhers.sif` (Ubuntu 24.04, single-threaded)
 
 | Library | Time per NAND gate |
 |:---:|:---:|
-| **TFHEpp** (C++, SPQLIOS-AVX512, `-O3`) | **6.450 ms** |
-| **tfhe-rs** (Rust, `DEFAULT_PARAMETERS`, 1 thread) | **5.897 ms** |
+| **TFHEpp** (C++, g++-14, SPQLIOS-AVX512, `-O3`) | **6.17 ms** |
+| **tfhe-rs** (Rust, `DEFAULT_PARAMETERS`, 1 thread) | **5.83 ms** |
 
 ## Reproducing locally (Apptainer)
 

compare-tfhers.def

@@ -42,7 +42,7 @@ From: ubuntu:24.04
     apt-get update
     apt-get upgrade -y
     apt-get install -y \
-        build-essential g++ libomp-dev cmake ninja-build \
+        build-essential g++-14 libomp-dev cmake ninja-build \
         git curl wget ca-certificates
 
     # ── Rust toolchain (stable + let tfhe-rs pin its own version) ────────────
@@ -57,6 +57,8 @@ From: ubuntu:24.04
     # ── Build TFHEpp pbs_tfhers benchmark ────────────────────────────────────
     cmake . -B build -G Ninja \
         -DCMAKE_BUILD_TYPE=Release \
+        -DCMAKE_CXX_COMPILER=g++-14 \
+        -DCMAKE_C_COMPILER=gcc-14 \
         -DUSE_TFHE_RS=ON \
         -DENABLE_TEST=ON
     cmake --build build --target pbs_tfhers