From 55634c1f52e9bdaadeba6a5a6f836b2bd2666d65 Mon Sep 17 00:00:00 2001
From: Konstantin Matskevich <konstantin.matskevich@itseez.com>
Date: Mon, 30 Dec 2013 13:06:32 +0400
Subject: [PATCH] fix

---
 modules/core/include/opencv2/core/ocl.hpp |  1 +
 modules/core/src/ocl.cpp                  | 10 ++++++++++
 modules/imgproc/src/clahe.cpp             |  4 +++-
 3 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/modules/core/include/opencv2/core/ocl.hpp b/modules/core/include/opencv2/core/ocl.hpp
index 3112766796..e3805bcdc1 100644
--- a/modules/core/include/opencv2/core/ocl.hpp
+++ b/modules/core/include/opencv2/core/ocl.hpp
@@ -489,6 +489,7 @@ public:
     bool runTask(bool sync, const Queue& q=Queue());
 
     size_t workGroupSize() const;
+    size_t preferedWorkGroupSizeMultiple() const;
     bool compileWorkGroupSize(size_t wsz[]) const;
     size_t localMemSize() const;
 
diff --git a/modules/core/src/ocl.cpp b/modules/core/src/ocl.cpp
index 7b64440513..2369c470e3 100644
--- a/modules/core/src/ocl.cpp
+++ b/modules/core/src/ocl.cpp
@@ -2813,6 +2813,16 @@ size_t Kernel::workGroupSize() const
                                     sizeof(val), &val, &retsz) >= 0 ? val : 0;
 }
 
+size_t Kernel::preferedWorkGroupSizeMultiple() const
+{
+    if(!p)
+        return 0;
+    size_t val = 0, retsz = 0;
+    cl_device_id dev = (cl_device_id)Device::getDefault().ptr();
+    return clGetKernelWorkGroupInfo(p->handle, dev, CL_KERNEL_PREFERRED_WORK_GROUP_SIZE_MULTIPLE,
+                                    sizeof(val), &val, &retsz) >= 0 ? val : 0;
+}
+
 bool Kernel::compileWorkGroupSize(size_t wsz[]) const
 {
     if(!p || !wsz)
diff --git a/modules/imgproc/src/clahe.cpp b/modules/imgproc/src/clahe.cpp
index c4646b40a5..079e635f94 100644
--- a/modules/imgproc/src/clahe.cpp
+++ b/modules/imgproc/src/clahe.cpp
@@ -51,12 +51,14 @@ namespace clahe
         const int tilesX, const int tilesY, const cv::Size tileSize,
         const int clipLimit, const float lutScale)
     {
+        cv::ocl::Kernel _k("calcLut", cv::ocl::imgproc::clahe_oclsrc);
+
         bool is_cpu = cv::ocl::Device::getDefault().type() == cv::ocl::Device::TYPE_CPU;
         cv::String opts;
         if(is_cpu)
             opts = "-D CPU ";
         else
-            opts = cv::format("-D WAVE_SIZE=%d", cv::ocl::Device::getDefault().maxWorkGroupSize());
+            opts = cv::format("-D WAVE_SIZE=%d", _k.preferedWorkGroupSizeMultiple());
 
         cv::ocl::Kernel k("calcLut", cv::ocl::imgproc::clahe_oclsrc, opts);
         if(k.empty())
-- 
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