Two graphics cards in one computer, How to make decision when createdevice!

Don't rank by them by video-memory size -- integrated cards often report the entire system ram size in there, which will be more than what the "real" GPU has.
If you add this code into one of your CPP files, it tells hybrid laptops that you want to use the "real" GPU by default.

extern "C" { // Hint to Hybrid laptop drivers that our app would really rather use the NVidia/AMD GPU that you've got sitting over there rather than Intel Graphics...
	_declspec(dllexport) DWORD NvOptimusEnablement = 0x00000001;
	_declspec(dllexport) int AmdPowerXpressRequestHighPerformance = 1;
}

Then if you just pass NULL for the adaptor argument in D3D11CreateDevice, you should get the right one by default. This is generally the right thing to do as it leaves the decision up to the OS and the driver. The user can actually choose which GPU is the default under their driver control panel on most laptops!

Alternatively, yeah, give the choice to the user and let them pick one. You could have "auto" as an option too, in which case you just use NULL.

Or if you want to find out if there are multiple GPU's from different vendors, you could use something like this:

		int nvidia = -1;
		int amd = -1;
		int intel = -1;
		uint count = 0;
		for( uint adapterIdx = 0; dxgiFactory->EnumAdapters( adapterIdx, &adapter ) != DXGI_ERROR_NOT_FOUND; ++adapterIdx, ++count )
		{
			DXGI_ADAPTER_DESC adapterDesc;
			adapter->GetDesc( &adapterDesc );
			if( wcsstr( adapterDesc.Description, L"Intel" ) )
				intel = adapterIdx;
			else if( wcsstr( adapterDesc.Description, L"NVIDIA" ) )
				nvidia = adapterIdx;
			else if( wcsstr( adapterDesc.Description, L"AMD" ) )
				amd = adapterIdx;
			adapter->Release();
			adapter = 0;
		}

You can then rank the NVidia GPU's against each other based on video memory size, the Intels against each other based on video memory size, etc...

Thanks a lot ,Hodgman

Then if you just pass NULL for the adaptor argument in D3D11CreateDevice, you should get the right one by default. This is generally the right thing to do as it leaves the decision up to the OS and the driver

I did as you told me ,

			hr = D3D11API->D3D11DynamicCreateDevice(
				nullptr,
				eD3DDriverType,
				nullptr,
				creationFlags,
				&FeatureLevel,
				numFeatureLevels,
				D3D11_SDK_VERSION,
				&m_pD3D11Device,
				&selectedFeatureLevel,
				&m_pD3D11DeviceContext);

the return error code is 80070057,

HRESULT: 0x80070057 (2147942487)
Name: E_INVALIDARG
Description: An invalid parameter was passed to the returning function
Severity code: Failed
Facility Code: FACILITY_WIN32 (7)
Error Code: 0x0057 (87)

I do not know, I will try it letter?

I would definitely suggest providing a proper UI (and/or command line argument) for selecting the adapter. Many many PC's have multiple video cards in them, and Windows 10 now has much better support for so-called "hybrid" systems without having to go through proprietary layers like Optimus.

Also, make sure that you're passing "D3D_DRIVER_TYPE_HARDWARE" if you're passing NULL as the adapter to D3D11CreateDevice.

Don't rank by them by video-memory size -- integrated cards often report the entire system ram size in there, which will be more than what the "real" GPU has.
If you add this code into one of your CPP files, it tells hybrid laptops that you want to use the "real" GPU by default.

extern "C" { // Hint to Hybrid laptop drivers that our app would really rather use the NVidia/AMD GPU that you've got sitting over there rather than Intel Graphics...
	_declspec(dllexport) DWORD NvOptimusEnablement = 0x00000001;
	_declspec(dllexport) int AmdPowerXpressRequestHighPerformance = 1;
}

Then if you just pass NULL for the adaptor argument in D3D11CreateDevice, you should get the right one by default. This is generally the right thing to do as it leaves the decision up to the OS and the driver. The user can actually choose which GPU is the default under their driver control panel on most laptops!

What does this mean? This means the system will choose the best video card to create device. If the user have two cards , Intel HD and nvidia 960,and user set intel hd card as the main output, the I configured as you suggestions ,the system will choose nvidia card automatically?? It's really bothering me.

I would definitely suggest providing a proper UI (and/or command line argument) for selecting the adapter. Many many PC's have multiple video cards in them, and Windows 10 now has much better support for so-called "hybrid" systems without having to go through proprietary layers like Optimus.

Also, make sure that you're passing "D3D_DRIVER_TYPE_HARDWARE" if you're passing NULL as the adapter to D3D11CreateDevice.

proprietary layers like Optimus. Is this just the way hodgman suggested?