Context

Table of Contents

• Context Initialization
• Current System Time
• Programmable Vision Accelerator
• CUDA Task-Graph

The NVIDIA^® DriveWorks Context module stores all global components, including:

• Pointer logging callbacks.
• NvMedia Device instance.
• Global timesource.
• Platform information.
• Virtual file system.

Every module requires a handle to a valid context instance. When a module is created within a certain context, it functions only within that context. Outside of this context, it does not exist.

Context Initialization

The DriveWorks SDK context must be initialized before any other DriveWorks module. A typical context initialization looks like the following:

#include <dw/core/context/Context.h>
#include <dw/core/base/VersionCurrent.h>
 
...
 
// initialize SDK context, using data folder
dwContextParameters contextParams = {};
contextParams.dataPath            = "path/to/location/of/resources.pak/folder";
contextParams.eglDisplay          = getEGLDisplay();  // on DRIVE platforms this should point to right EGL display, on x86 just nullptr
 
// Initialize DriveWorks context
dwInitialize(&sdkContext, DW_VERSION, &contextParams);
 
...
// do processing
...
 
// release SDK context
dwRelease(&sdkContext);

Note

If a nullptr is passed for dataPath, then a data folder is looked for in typical install locations in relation to the current driveworks library install location. If a data directory is still not found then virtual file system will be unavailable. When that happens, modules that use certain DNN networks will not function properly.

When modules call dwInitialize(), they usually pass DW_VERSION as the argument that specifies the current DriveWorks API version. dwInitialize() uses that argument to ensure the version of the API headers and the library match. After that, the function initializes all context subcomponents.

During the initialization phase, DriveWorks initializes:

• NVIDIA^® CUDA^®
• DLA (applies only to NVIDIA DRIVE^™ platforms)
• OpenGL extensions, if OpenGL is available
• NvMedia components, if running on an NVIDIA DRVE^™ platform

Current System Time

An SDK context provides access to the common clock used within all SDK modules. For event timestamps, DriveWorks uses a high-resolution monotonic clock with microseconds precision. Sensor samples are an example of event timestamps. Any module accepting dwTime_t as input argument, assumes the time is in the right units and is from the same domain.

// get current system time
dwTime_t now = 0;
dwContext_getCurrentTime(&now, sdkContext);
 
printf("Time now is %f [sec]\n", now / 1e6);

Note

The returned time is based on UNIX Epoch time.

Programmable Vision Accelerator

An SDK context provides the possibility to enable PVA (Programmable Vision Accelerator) on NVIDIA DRVE^™ platforms.

If PVA is not enabled, modules that execute on PVA will not work properly. PVA can be enabled during context initialization like this:

...
// other initialization parameters
...
 
// Enable PVA
contextParams.enablePVA           = true;
 
// Initialize DriveWorks context
dwInitialize(&sdkContext, DW_VERSION, &contextParams);
 
...
// do processing
...
 
// release SDK context
dwRelease(&sdkContext);

Note

There can be maximum 8 SDK contexts with PVA running simultaneously on an NVIDIA DRVE^™ platform.

CUDA Task-Graph

An SDK context can be initialized with CUDA Task-Graph enabled.

If it is enabled, CUDA Task-Graph will be used where applicable; such as, DNN inference for models that support this sort of execution. CUDA Task-Graph can be enabled during context initialization like this:

...
// other initialization parameters
...
 
// Enable CUDA Task-Graph
contextParams.enableCudaTaskGraph = true;
 
// Initialize DriveWorks context
dwInitialize(&sdkContext, DW_VERSION, &contextParams);
 
...
// do processing
...
 
// release SDK context
dwRelease(&sdkContext);