add another tester for the suggested local work size

This tester allows setting the global work size via
command line arguments.

Author: bashbaug

samples/00_suggestedlocalworksize/CMakeLists.txt

@@ -0,0 +1,10 @@
+# Copyright (c) 2026 Ben Ashbaugh
+#
+# SPDX-License-Identifier: MIT
+
+add_opencl_sample(
+    TEST
+    NUMBER 00
+    TARGET suggestedlocalworksize
+    VERSION 120
+    SOURCES main.cpp)

samples/00_suggestedlocalworksize/main.cpp

@@ -0,0 +1,116 @@
+/*
+// Copyright (c) 2019-2026 Ben Ashbaugh
+//
+// SPDX-License-Identifier: MIT
+*/
+
+#include <popl/popl.hpp>
+
+#include <CL/opencl.hpp>
+
+#include "util.hpp"
+
+static const char kernelString[] = R"CLC(
+kernel void test(global uint* dst)
+{
+    uint id = get_global_id(0);
+    dst[id] = id;
+}
+)CLC";
+
+#if !defined(cl_khr_suggested_local_work_size)
+#pragma message("suggestedlocalworksize: cl_khr_suggested_local_work_size.  Please update your OpenCL headers.")
+#endif
+
+int main(int argc, char** argv)
+{
+    int platformIndex = 0;
+    int deviceIndex = 0;
+
+    size_t gws = 1024*1024;
+
+    {
+        popl::OptionParser op("Supported Options");
+        op.add<popl::Value<int>>("p", "platform", "Platform Index", platformIndex, &platformIndex);
+        op.add<popl::Value<int>>("d", "device", "Device Index", deviceIndex, &deviceIndex);
+        op.add<popl::Value<size_t>>("g", "gws", "Global Work Size", gws, &gws);
+
+        bool printUsage = false;
+        try {
+            op.parse(argc, argv);
+        } catch (std::exception& e) {
+            fprintf(stderr, "Error: %s\n\n", e.what());
+            printUsage = true;
+        }
+
+        if (printUsage || !op.unknown_options().empty() || !op.non_option_args().empty()) {
+            fprintf(stderr,
+                "Usage: suggestedlocalworksize [options]\n"
+                "%s", op.help().c_str());
+            return -1;
+        }
+    }
+
+    std::vector<cl::Platform> platforms;
+    cl::Platform::get(&platforms);
+
+    if (!checkPlatformIndex(platforms, platformIndex)) {
+        return -1;
+    }
+
+    printf("Running on platform: %s\n",
+        platforms[platformIndex].getInfo<CL_PLATFORM_NAME>().c_str() );
+
+    std::vector<cl::Device> devices;
+    platforms[platformIndex].getDevices(CL_DEVICE_TYPE_ALL, &devices);
+
+    printf("Running on device: %s\n",
+        devices[deviceIndex].getInfo<CL_DEVICE_NAME>().c_str() );
+
+    if (checkDeviceForExtension(devices[deviceIndex], CL_KHR_SUGGESTED_LOCAL_WORK_SIZE_EXTENSION_NAME)) {
+        printf("Device supports %s.\n", CL_KHR_SUGGESTED_LOCAL_WORK_SIZE_EXTENSION_NAME);
+    } else {
+        printf("Device does not support %s, exiting.\n", CL_KHR_SUGGESTED_LOCAL_WORK_SIZE_EXTENSION_NAME);
+        return -1;
+    }
+
+    clGetKernelSuggestedLocalWorkSizeKHR_fn clGetKernelSuggestedLocalWorkSizeKHR =
+        (clGetKernelSuggestedLocalWorkSizeKHR_fn)clGetExtensionFunctionAddressForPlatform(
+            platforms[platformIndex](),
+            "clGetKernelSuggestedLocalWorkSizeKHR" );
+    if (clGetKernelSuggestedLocalWorkSizeKHR == nullptr) {
+        fprintf(stderr, "Failed to get function pointer for clGetKernelSuggestedLocalWorkSizeKHR, exiting.\n");
+        return -1;
+    }
+
+    cl::Context context{devices[deviceIndex]};
+    cl::CommandQueue commandQueue{context, devices[deviceIndex]};
+
+    cl::Program program{ context, kernelString };
+    program.build();
+    cl::Kernel kernel = cl::Kernel{ program, "test" };
+
+    cl::Buffer buf = cl::Buffer{
+        context,
+        CL_MEM_ALLOC_HOST_PTR,
+        gws * sizeof( cl_uint ) };
+
+    kernel.setArg(0, buf);
+
+    size_t suggestedLocalWorkSize = 0;
+    cl_int errorCode = clGetKernelSuggestedLocalWorkSizeKHR(
+        commandQueue(),
+        kernel(),
+        1,
+        nullptr,
+        &gws,
+        &suggestedLocalWorkSize );
+
+    if (errorCode != CL_SUCCESS) {
+        fprintf(stderr, "clGetKernelSuggestedLocalWorkSizeKHR failed with error code %d, exiting.\n", errorCode);
+        return -1;
+    }
+
+    printf("Suggested local work size for global work size %zu is: %zu\n", gws, suggestedLocalWorkSize);
+    return 0;
+}

samples/CMakeLists.txt

@@ -66,6 +66,7 @@ add_subdirectory( 00_extendeddevicequeries )
 add_subdirectory( 00_loaderinfo )
 add_subdirectory( 00_newqueries )
 add_subdirectory( 00_newqueriespp )
+add_subdirectory( 00_suggestedlocalworksize )
 add_subdirectory( 01_copybuffer )
 add_subdirectory( 02_copybufferkernel )
 add_subdirectory( 03_mandelbrot )