From 781c04324eab9537dc3ddb0b01f75975990b8e14 Mon Sep 17 00:00:00 2001
From: "marina.kolpakova" <marina.kolpakova@itseez.com>
Date: Wed, 14 Nov 2012 14:47:00 +0400
Subject: [PATCH] refactor: PrefixSum

---
 modules/gpu/src/cuda/isf-sc.cu | 60 ++++++++++++++++++++--------------
 1 file changed, 35 insertions(+), 25 deletions(-)

diff --git a/modules/gpu/src/cuda/isf-sc.cu b/modules/gpu/src/cuda/isf-sc.cu
index a4496bf678..27d60e6372 100644
--- a/modules/gpu/src/cuda/isf-sc.cu
+++ b/modules/gpu/src/cuda/isf-sc.cu
@@ -79,6 +79,39 @@ namespace icf {
         }
     }
 
+    template<typename Policy>
+    struct PrefixSum
+    {
+    __device static void apply(float& impact)
+        {
+    #if defined __CUDA_ARCH__ && __CUDA_ARCH__ >= 300
+    #pragma unroll
+            // scan on shuffl functions
+            for (int i = 1; i < Policy::WARP; i *= 2)
+            {
+                const float n = __shfl_up(impact, i, Policy::WARP);
+
+                if (threadIdx.x >= i)
+                    impact += n;
+            }
+    #else
+            __shared__ volatile float ptr[Policy::STA_X * Policy::STA_Y];
+
+            const int idx = threadIdx.y * Policy::STA_X + threadIdx.x;
+
+            ptr[idx] = impact;
+
+            if ( threadIdx.x >=  1) ptr [idx ] = (ptr [idx -  1] + ptr [idx]);
+            if ( threadIdx.x >=  2) ptr [idx ] = (ptr [idx -  2] + ptr [idx]);
+            if ( threadIdx.x >=  4) ptr [idx ] = (ptr [idx -  4] + ptr [idx]);
+            if ( threadIdx.x >=  8) ptr [idx ] = (ptr [idx -  8] + ptr [idx]);
+            if ( threadIdx.x >= 16) ptr [idx ] = (ptr [idx - 16] + ptr [idx]);
+
+            impact = ptr[idx];
+    #endif
+        }
+    };
+
     texture<int,  cudaTextureType2D, cudaReadModeElementType> thogluv;
 
     template<bool isUp>
@@ -201,32 +234,9 @@ __device void CascadeInvoker<Policy>::detect(Detection* objects, const uint ndet
         const int lShift = (next - 1) * 2 + (int)(sum >= threshold);
         float impact = leaves[(st + threadIdx.x) * 4 + lShift];
 
-#if defined __CUDA_ARCH__ && __CUDA_ARCH__ >= 300
-#pragma unroll
-        // scan on shuffl functions
-        for (int i = 1; i < Policy::WARP; i *= 2)
-        {
-            const float n = __shfl_up(impact, i, Policy::WARP);
-
-            if (threadIdx.x >= i)
-                impact += n;
-        }
-#else
-        __shared__ volatile float ptr[Policy::STA_X * Policy::STA_Y];
-
-        const int idx = threadIdx.y * Policy::STA_X + threadIdx.x;
-
-        ptr[idx] = impact;
-
-        if ( threadIdx.x >=  1) ptr [idx ] = (ptr [idx -  1] + ptr [idx]);
-        if ( threadIdx.x >=  2) ptr [idx ] = (ptr [idx -  2] + ptr [idx]);
-        if ( threadIdx.x >=  4) ptr [idx ] = (ptr [idx -  4] + ptr [idx]);
-        if ( threadIdx.x >=  8) ptr [idx ] = (ptr [idx -  8] + ptr [idx]);
-        if ( threadIdx.x >= 16) ptr [idx ] = (ptr [idx - 16] + ptr [idx]);
-
-        impact = ptr[idx];
-#endif
+        PrefixSum<Policy>::apply(impact);
         confidence += impact;
+
         if(__any((confidence <= stages[(st + threadIdx.x)]))) st += 2048;
     }