pytorch · ShamSaleem · Sep 6, 2026
@@ -64,7 +64,7 @@ cmake \
   -DEXECUTORCH_BUILD_KERNELS_QUANTIZED=ON \
   -DEXECUTORCH_BUILD_FLATC=ON \
   -Bcmake-out-arm .
-cmake --build cmake-out-arm --config Release -j$(nproc)
+cmake --build cmake-out-arm --config Release -j$(( $(nproc 2>/dev/null || sysctl -n hw.ncpu) + 1 ))
 
 # 2. Build the pack. --output-dir is where the .pack archive lands
 #    (created if absent); each invocation rewrites this directory.

@@ -91,7 +91,7 @@ cmake -S examples/arm/executor_runner/standalone \
       -DETHOSU_TARGET_NPU_CONFIG=ethos-u55-128 \
       -DMEMORY_MODE=Shared_Sram \
       -DSYSTEM_CONFIG=Ethos_U55_High_End_Embedded
-cmake --build ethos_u_minimal_example -j$(nproc) -- arm_executor_runner
+cmake --build ethos_u_minimal_example -j$(( $(nproc 2>/dev/null || sysctl -n hw.ncpu) + 1 )) -- arm_executor_runner
 ```
 
 ```{tip}

@@ -144,7 +144,7 @@ cmake --preset arm-baremetal \
   -DCMAKE_BUILD_TYPE=Release \
   -DEXECUTORCH_BUILD_DEVTOOLS=ON \
   -Bcmake-out-arm
-cmake --build cmake-out-arm --target install -j$(nproc)
+cmake --build cmake-out-arm --target install -j$(( $(nproc 2>/dev/null || sysctl -n hw.ncpu) + 1 ))
 
 # Build the executor runner, linking the .pte into the binary
 cmake -DCMAKE_TOOLCHAIN_FILE=$(pwd)/examples/arm/ethos-u-setup/arm-none-eabi-gcc.cmake \
@@ -153,7 +153,7 @@ cmake -DCMAKE_TOOLCHAIN_FILE=$(pwd)/examples/arm/ethos-u-setup/arm-none-eabi-gcc
       -DTARGET_CPU=cortex-m55 \
       -Bbuild \
       examples/arm/executor_runner
-cmake --build build -j$(nproc) -- arm_executor_runner
+cmake --build build -j$(( $(nproc 2>/dev/null || sysctl -n hw.ncpu) + 1 )) -- arm_executor_runner
 ```
 
 Run on a simulated Cortex-M target:

@@ -164,7 +164,7 @@ cmake -S examples/arm/executor_runner/standalone \
       -DETHOSU_TARGET_NPU_CONFIG=ethos-u55-128 \
       -DMEMORY_MODE=Shared_Sram \
       -DSYSTEM_CONFIG=Ethos_U55_High_End_Embedded
-cmake --build ethos_u_minimal_example -j$(nproc) -- arm_executor_runner
+cmake --build ethos_u_minimal_example -j$(( $(nproc 2>/dev/null || sysctl -n hw.ncpu) + 1 )) -- arm_executor_runner
 ```
 
 ```{tip}

@@ -129,14 +129,14 @@
    "execution_count": null,
    "metadata": {},
    "outputs": [],
-   "source": "%%bash\n\n# Build executorch libraries cross-compiled for arm baremetal to executorch/cmake-out-arm\ncmake --preset arm-baremetal \\\n-DCMAKE_BUILD_TYPE=Release \\\n-DEXECUTORCH_BUILD_DEVTOOLS=ON \\\n-B../../cmake-out-arm ../..\ncmake --build ../../cmake-out-arm --target install -j$(nproc) \n"
+   "source": "%%bash\n\n# Build executorch libraries cross-compiled for arm baremetal to executorch/cmake-out-arm\ncmake --preset arm-baremetal \\\n-DCMAKE_BUILD_TYPE=Release \\\n-DEXECUTORCH_BUILD_DEVTOOLS=ON \\\n-B../../cmake-out-arm ../..\ncmake --build ../../cmake-out-arm --target install -j$(( $(nproc 2>/dev/null || sysctl -n hw.ncpu) + 1 )) \n"
   },
   {
    "cell_type": "code",
    "execution_count": null,
    "metadata": {},
    "outputs": [],
-   "source": "%%bash \n# Build example executor runner application to examples/arm/cortex_m_mv2_example\n# Note that this is the same runner as used in the Ethos-U example, creating some overlap in the config even though the Ethos-U is not used.\ncmake -DCMAKE_TOOLCHAIN_FILE=$(pwd)/ethos-u-setup/arm-none-eabi-gcc.cmake \\\n      -DCMAKE_BUILD_TYPE=Release \\\n      -DET_PTE_FILE_PATH=cortex_m_mv2_example.bpte \\\n      -DTARGET_CPU=cortex-m55 \\\n      -DETHOSU_TARGET_NPU_CONFIG=ethos-u55-128 \\\n      -DMEMORY_MODE=Shared_Sram \\\n      -DET_BUNDLE_IO=ON \\\n      -DSYSTEM_CONFIG=Ethos_U55_High_End_Embedded \\\n      -Bcortex_m_mv2_example \\\n      -S executor_runner/standalone\ncmake --build cortex_m_mv2_example -j$(nproc) -- arm_executor_runner"
+   "source": "%%bash \n# Build example executor runner application to examples/arm/cortex_m_mv2_example\n# Note that this is the same runner as used in the Ethos-U example, creating some overlap in the config even though the Ethos-U is not used.\ncmake -DCMAKE_TOOLCHAIN_FILE=$(pwd)/ethos-u-setup/arm-none-eabi-gcc.cmake \\\n      -DCMAKE_BUILD_TYPE=Release \\\n      -DET_PTE_FILE_PATH=cortex_m_mv2_example.bpte \\\n      -DTARGET_CPU=cortex-m55 \\\n      -DETHOSU_TARGET_NPU_CONFIG=ethos-u55-128 \\\n      -DMEMORY_MODE=Shared_Sram \\\n      -DET_BUNDLE_IO=ON \\\n      -DSYSTEM_CONFIG=Ethos_U55_High_End_Embedded \\\n      -Bcortex_m_mv2_example \\\n      -S executor_runner/standalone\ncmake --build cortex_m_mv2_example -j$(( $(nproc 2>/dev/null || sysctl -n hw.ncpu) + 1 )) -- arm_executor_runner"
   },
   {
    "cell_type": "markdown",

@@ -206,7 +206,7 @@
     "      -DSYSTEM_CONFIG=Ethos_U55_High_End_Embedded \\\n",
     "      -Bethos_u_cmsis_nn_fallback_example \\\n",
     "      -S executor_runner/standalone\n",
-    "cmake --build ethos_u_cmsis_nn_fallback_example -j$(nproc) -- arm_executor_runner"
+    "cmake --build ethos_u_cmsis_nn_fallback_example -j$(( $(nproc 2>/dev/null || sysctl -n hw.ncpu) + 1 )) -- arm_executor_runner"
    ]
   },
   {

@@ -196,7 +196,7 @@
     "      -DSYSTEM_CONFIG=Ethos_U55_High_End_Embedded \\\n",
     "      -Bethos_u_minimal_example \\\n",
     "      -S executor_runner/standalone\n",
-    "cmake --build ethos_u_minimal_example -j$(nproc) -- arm_executor_runner"
+    "cmake --build ethos_u_minimal_example -j$(( $(nproc 2>/dev/null || sysctl -n hw.ncpu) + 1 )) -- arm_executor_runner"
    ]
   },
   {

@@ -8,7 +8,7 @@
 $ cmake --preset arm-baremetal \
 -DCMAKE_BUILD_TYPE=Release \
 -B../../cmake-out-arm ../..
-cmake --build ../../cmake-out-arm --target install -j$(nproc)
+cmake --build ../../cmake-out-arm --target install -j$(( $(nproc 2>/dev/null || sysctl -n hw.ncpu) + 1 ))
 ```
 
 3. Set up the build system. You need to provide path to the DEiT-Tiny pte generated in the
@@ -21,7 +21,7 @@ $ cmake -DCMAKE_TOOLCHAIN_FILE=$(pwd)/ethos-u-setup/arm-none-eabi-gcc.cmake -DET
 4. Compile the application.
 
 ```
-$ cmake --build simple_app_deit_tiny -j$(nproc) -- img_class_example
+$ cmake --build simple_app_deit_tiny -j$(( $(nproc 2>/dev/null || sysctl -n hw.ncpu) + 1 )) -- img_class_example
 ```
 
 5. Deploy the application on the Corstone-320 Fixed Virtual Platform. Assuming you have the Corstone-320 installed on your path, do the following command to deploy the application.

@@ -19,7 +19,7 @@ Build and install the Arm bare-metal ExecuTorch libraries from
 cmake --preset arm-baremetal \
   -DCMAKE_BUILD_TYPE=Release \
   -B../../cmake-out-arm ../..
-cmake --build ../../cmake-out-arm --target install -j$(nproc)
+cmake --build ../../cmake-out-arm --target install -j$(( $(nproc 2>/dev/null || sysctl -n hw.ncpu) + 1 ))
 ```
 
 The Arm bare-metal preset installs into the build directory. If you use a
@@ -67,7 +67,7 @@ can inspect and retune post-processing without re-exporting the graph.
 ## Compile
 
 ```bash
-cmake --build mobilesam_point_runtime -j$(nproc) -- mobilesam_prompt_segmentation_example
+cmake --build mobilesam_point_runtime -j$(( $(nproc 2>/dev/null || sysctl -n hw.ncpu) + 1 )) -- mobilesam_prompt_segmentation_example
 ```
 
 ## Run on Corstone-320 FVP

@@ -432,7 +432,7 @@
     "cmake --preset arm-baremetal \\\n",
     "-DCMAKE_BUILD_TYPE=Release \\\n",
     "-B../../cmake-out-arm ../..\n",
-    "cmake --build ../../cmake-out-arm --target install -j$(nproc) "
+    "cmake --build ../../cmake-out-arm --target install -j$(( $(nproc 2>/dev/null || sysctl -n hw.ncpu) + 1 )) "
    ]
   },
   {
@@ -454,7 +454,7 @@
     "      -DSYSTEM_CONFIG=Ethos_U85_SYS_DRAM_Mid \\\n",
     "      -Bethos_u_original_model \\\n",
     "      -S executor_runner/standalone\n",
-    "cmake --build ethos_u_original_model -j$(nproc) -- arm_executor_runner"
+    "cmake --build ethos_u_original_model -j$(( $(nproc 2>/dev/null || sysctl -n hw.ncpu) + 1 )) -- arm_executor_runner"
    ]
   },
   {
@@ -500,7 +500,7 @@
     "      -DSYSTEM_CONFIG=Ethos_U85_SYS_DRAM_Mid \\\n",
     "      -Bethos_u_pruned_model \\\n",
     "      -S executor_runner/standalone\n",
-    "cmake --build ethos_u_pruned_model -j$(nproc) -- arm_executor_runner"
+    "cmake --build ethos_u_pruned_model -j$(( $(nproc 2>/dev/null || sysctl -n hw.ncpu) + 1 )) -- arm_executor_runner"
    ]
   },
   {