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render/renderutils/c_src/common.cpp

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+/*
+ * Copyright (c) 2020-2022 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+ *
+ * NVIDIA CORPORATION, its affiliates and licensors retain all intellectual
+ * property and proprietary rights in and to this material, related 
+ * documentation and any modifications thereto. Any use, reproduction, 
+ * disclosure or distribution of this material and related documentation
+ * without an express license agreement from NVIDIA CORPORATION or 
+ * its affiliates is strictly prohibited.
+ */
+
+#include <cuda_runtime.h>
+#include <algorithm>
+
+//------------------------------------------------------------------------
+// Block and grid size calculators for kernel launches.
+
+dim3 getLaunchBlockSize(int maxWidth, int maxHeight, dim3 dims)
+{
+    int maxThreads = maxWidth * maxHeight;
+    if (maxThreads <= 1 || (dims.x * dims.y) <= 1)
+        return dim3(1, 1, 1); // Degenerate.
+
+    // Start from max size.
+    int bw = maxWidth;
+    int bh = maxHeight;
+
+    // Optimizations for weirdly sized buffers.
+    if (dims.x < bw)
+    {
+        // Decrease block width to smallest power of two that covers the buffer width.
+        while ((bw >> 1) >= dims.x)
+            bw >>= 1;
+
+        // Maximize height.
+        bh = maxThreads / bw;
+        if (bh > dims.y)
+            bh = dims.y;
+    }
+    else if (dims.y < bh)
+    {
+        // Halve height and double width until fits completely inside buffer vertically.
+        while (bh > dims.y)
+        {
+            bh >>= 1;
+            if (bw < dims.x)
+                bw <<= 1;
+        }
+    }
+
+    // Done.
+    return dim3(bw, bh, 1);
+}
+
+// returns the size of a block that can be reduced using horizontal SIMD operations (e.g. __shfl_xor_sync)
+dim3 getWarpSize(dim3 blockSize)
+{
+    return dim3(
+        std::min(blockSize.x, 32u), 
+        std::min(std::max(32u / blockSize.x, 1u), std::min(32u, blockSize.y)), 
+        std::min(std::max(32u / (blockSize.x * blockSize.y), 1u), std::min(32u, blockSize.z))
+    );
+}
+
+dim3 getLaunchGridSize(dim3 blockSize, dim3 dims)
+{
+    dim3 gridSize;
+    gridSize.x = (dims.x  - 1) / blockSize.x + 1;
+    gridSize.y = (dims.y - 1) / blockSize.y + 1;
+    gridSize.z = (dims.z  - 1) / blockSize.z + 1;
+    return gridSize;
+}
+
+//------------------------------------------------------------------------