bitonic sort sample by CrabExtra · Pull Request #209 · Devsh-Graphics-Programming/Nabla-Examples-and-Tests

CrabExtra · 2025-08-11T18:31:33Z

No description provided.

…ng/Nabla-Examples-and-Tests into bxdf_unit_tests

devshgraphicsprogramming · 2025-11-08T22:26:38Z

13_BitonicSort/app_resources/bitonic_sort_shader.comp.hlsl

+struct Accessor
+{
+	static Accessor create(const uint64_t address)
+	{
+		Accessor accessor;
+		accessor.address = address;
+		return accessor;
+	}
+
+	template <typename AccessType, typename IndexType>
+	void get(const IndexType index, NBL_REF_ARG(AccessType) value)
+	{
+		value = vk::RawBufferLoad<AccessType>(address + index * sizeof(AccessType));
+	}
+
+	template <typename AccessType, typename IndexType>
+	void set(const IndexType index, const AccessType value)
+	{
+		vk::RawBufferStore<AccessType>(address + index * sizeof(AccessType), value);
+	}
+
+	uint64_t address;
+};


there's readymade BDA accessors you can use AFAIK

devshgraphicsprogramming · 2025-11-08T22:27:55Z

CMakeLists.txt

-	add_subdirectory(12_MeshLoaders)
-	#
-	#add_subdirectory(13_MaterialCompiler EXCLUDE_FROM_ALL)
+	add_subdirectory(12_MeshLoaders EXCLUDE_FROM_ALL)


you erroneously added EXCLUDE_FROM_ALL to example 12 and now its omitted from CI

devshgraphicsprogramming · 2025-11-08T22:32:20Z

13_BitonicSort/app_resources/common.hlsl

+	uint64_t deviceBufferAddress;
+};
+
+NBL_CONSTEXPR uint32_t WorkgroupSizeLog2 = 10;  // 1024 threads (2^10)


512 is optimal residency on all GPUs

so log2 of 9

devshgraphicsprogramming · 2025-11-08T22:33:05Z

13_BitonicSort/main.cpp

+					std::cout << "(" << key << "," << value << "), ";
+					if ((i + 1) % 20 == 0) {
+						std::cout << "\n";
+					}
+				}
+				std::cout << "\nElement count: " << elementCount << "\n";
+
+				bool is_sorted = true;
+				int32_t error_index = -1;
+				for (uint32_t i = 1; i < elementCount; i++) {
+					uint32_t prevKey = data[(i - 1) * 2];
+					uint32_t currKey = data[i * 2];
+					if (currKey < prevKey) {
+						is_sorted = false;
+						error_index = i;
+						break;
+					}
+				}
+
+				if (is_sorted) {
+					std::cout << "Array is correctly sorted!\n";
+				}
+				else {
+					std::cout << "Array is NOT sorted correctly!\n";
+					std::cout << "Error at index " << error_index << ":\n";
+					std::cout << "  Previous key [" << (error_index - 1) << "] = " << data[(error_index - 1) * 2] << "\n";
+					std::cout << "  Current key  [" << error_index << "] = " << data[error_index * 2] << "\n";
+					std::cout << "  (" << data[error_index * 2] << " < " << data[(error_index - 1) * 2] << " is WRONG!)\n";


please use m_logger instead of std::cout

devshgraphicsprogramming · 2025-11-10T10:02:20Z

13_BitonicSort/main.cpp

+
+			deviceLocalBufferParams.queueFamilyIndexCount = 1;
+			deviceLocalBufferParams.queueFamilyIndices = &queueFamilyIndex;
+			deviceLocalBufferParams.size = sizeof(uint32_t) * elementCount * 2;  // *2 because we store (key, value) pairs


have a struct like KeyValue so you can take a sizeof of it then

devshgraphicsprogramming · 2025-11-10T10:04:45Z

13_BitonicSort/app_resources/common.hlsl

+};
+
+NBL_CONSTEXPR uint32_t WorkgroupSizeLog2 = 10;  // 1024 threads (2^10)
+NBL_CONSTEXPR uint32_t ElementsPerThreadLog2 = 2;  // 4 elements per thread (2^2) - VIRTUAL THREADING!


I wouldn't really call that virtual threads, virtual threads is if you are able to make a workgroup of size lets say 512 behave as if its 4096

processing multiple elements per invocation is an orthogonal extra to that and it helps with subgroupShuffle utilization and loading from global memory

devshgraphicsprogramming · 2025-11-10T10:22:40Z

13_BitonicSort/main.cpp

+
+		IQueue* const queue = getComputeQueue();
+
+		const uint32_t inputSize = sizeof(uint32_t) * elementCount * 2;  // *2 because we store (key, value) pairs


compute this before making your m_deviceLocalBuffer and use it throughout

devshgraphicsprogramming · 2025-11-10T10:23:43Z

13_BitonicSort/main.cpp

+				inputPtr[i * 2] = key;
+				inputPtr[i * 2 + 1] = value;


again another reason to have a named struct so you're not doing this unreadable type punning

devshgraphicsprogramming · 2025-11-10T10:24:03Z

13_BitonicSort/main.cpp

+				std::cout << "(" << key << "," << value << "), ";
+				if ((i + 1) % 20 == 0) {
+					std::cout << "\n";
+				}
+			}
+			std::cout << "\nElement count: " << elementCount << "\n";


use the m_logger instead of std::cout

or an std::ostringstream and then m_logger to print the contents

devshgraphicsprogramming · 2025-11-10T10:28:55Z

13_BitonicSort/main.cpp

+			{
+				assert(dstOffset == 0 && size == outputSize);
+
+				std::cout << "Sorted array: ";


name it differently, Output ARray

"Sorted array" is confusing cause it makes me think you're outputting a reference sorted array on the CPU

devshgraphicsprogramming · 2025-11-10T10:35:02Z

13_BitonicSort/main.cpp

+
+			cmdbuf->pushConstants(m_pipeline->getLayout(), IShader::E_SHADER_STAGE::ESS_COMPUTE, 0u, sizeof(pc), &pc);
+
+			cmdbuf->dispatch(1, 1, 1);


I'd consider preparing multiple test data sets, right now you only have one random one, and having 1 workgroup per test (so still one dispatch).

I'd add:

all keys equal

keys already sorted

keys in exact reverse
as manual test cases.

Furthermore this should be a stable sort (unlike the a counting sort), its important to check things like stability so making some test with some neighbouring equal keys in the input array is important to check they have not changed places.

devshgraphicsprogramming · 2025-11-10T10:37:25Z

13_BitonicSort/main.cpp

+					if (currKey < prevKey) {
+						is_sorted = false;
+						error_index = i;
+						break;
+					}


because Bitonic should be stable, you should also check

else if (currKey==prevKey && currValue>prevValue) // check stability, this is why we've initialized the values in such a particular way { // fail, not to bad sorting but instability }

and also assert(curValue!=prevValue); because of how we initialized the values

keptsecret and others added 30 commits January 15, 2025 11:50

check util functions

3668d99

reciprocity test

a66dc44

negative value checks

b5d9778

Merge branch 'bxdf_unit_tests' of github.com:Devsh-Graphics-Programmi…

48cc64c

…ng/Nabla-Examples-and-Tests into bxdf_unit_tests

fix test orders

5df264a

Merge branch 'bxdf_unit_tests' of github.com:Devsh-Graphics-Programmi…

983efc3

…ng/Nabla-Examples-and-Tests into bxdf_unit_tests

use new param structs for bxdf funcs

e6e434a

print more info on error

d494e3d

Merge branch 'master' into bxdf_unit_tests

3305441

fix reciprocity test, adjust comparison

3625ad2

fixed reciprocity test

839d42c

test buckets of inf

a40ba94

bucket by polar coords

d0d5d93

chi2 test

c8f8dae

Merge branch 'master' into bxdf_unit_tests

8ea1538

Merge branch 'master' into bxdf_unit_tests

dcc2927

fix chi2 test, beckmann still error

8781cb0

add visualization option for chi2 samples

724acd5

fixed exr visualization

e1cbc1a

use bxdf traits in test, better chi2 vis

9387298

test config with json

df07bfd

Merge branch 'master' into bxdf_unit_tests

de11fe2

fixed json config bugs

da1a4ad

smooth dielectric tests

d7f7a87

fix pcg usage

111c11b

Merge branch 'master' into bxdf_unit_tests

83d8a92

update with master

db74fad

refactor according to changes with bxdf

f3144f1

added a compile shader test

5a9e8b5

fix compile test

a133452

keptsecret added 7 commits October 24, 2025 16:11

fixes to jacobian * ndf test

2664e6d

fixes to tests: jacobian, reciprocity, pdf usage

590788a

fixes to reciprocity test, custom interaction for PathOrigin, iso config

0f82f18

fixes to chi2 test

7200e58

refactor test

09d5d4a

Merge branch 'master' into bxdf_unit_tests

565e5ac

merge bxdf_unit_tests, fix conflicts

829ea34

devshgraphicsprogramming reviewed Nov 8, 2025

View reviewed changes

devshgraphicsprogramming reviewed Nov 10, 2025

View reviewed changes

devshgraphicsprogramming mentioned this pull request Nov 10, 2025

Bitonic_Sort Devsh-Graphics-Programming/Nabla#943

Open

CrabExtra closed this Nov 19, 2025

CrabExtra force-pushed the master branch from 2f3126f to e5d5ae2 Compare November 19, 2025 15:25

Add BitonicSort example and update CMakeLists

7345af0

CrabExtra reopened this Nov 19, 2025

CrabExtra added 3 commits December 1, 2025 23:08

Update common.hlsl

5c55c78

Update common.hlsl

cef2b74

Update bitonic_sort_shader.comp.hlsl

5a4e464

Fletterio closed this Dec 9, 2025

Fletterio mentioned this pull request Dec 9, 2025

Bitonic sort #234

Closed

Fletterio reopened this Dec 9, 2025


		IQueue* const queue = getComputeQueue();

		const uint32_t inputSize = sizeof(uint32_t) * elementCount * 2; // *2 because we store (key, value) pairs


		cmdbuf->pushConstants(m_pipeline->getLayout(), IShader::E_SHADER_STAGE::ESS_COMPUTE, 0u, sizeof(pc), &pc);

		cmdbuf->dispatch(1, 1, 1);

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CrabExtra commented Aug 11, 2025

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