device function wont return - gives unknown error will return when I hardcode a float but not from a

Accelerated Computing CUDA CUDA Programming and Performance
1

I am hoping for some help with a problem I am having with a device function. This function is called from my kernel. I want the function to interpolate a value for me. When I return the calculated value the function doesn’t work and gives “unknown error”. When I hard code a return value it works well. Please offer any suggestions you may have as I have exhausted the resources allocated by my brain at the moment. Thanks!

Here is the device function called from a working kernel:

__device__ float g_GetPartDepthAt(float3* pathPosition, float4* d_partTopSurface)

{

	float voxelSize = 0.08025;

 	int xDim = 104;

// 

	int xCeil = ceilf( (pathPosition->x) / voxelSize);

	int xFloor = floorf( (pathPosition->x) / voxelSize);

	float xDelta = (pathPosition->x) / voxelSize - xFloor;

// 

	int yCeil = ceilf( (pathPosition->y) / voxelSize);

	int yFloor = floorf( (pathPosition->y) / voxelSize);

	float yDelta = (pathPosition->y) / voxelSize - yFloor;

	int bottLeft = yFloor * xDim + xFloor;

	int topRight = yCeil * xDim + xCeil;

	int bottRight = yFloor * xDim + xCeil;

	int topLeft = yCeil * xDim + xFloor;

	float distX0_Y0 = d_blankTopSurface[bottLeft].w;

	float distX1_Y1 = d_blankTopSurface[topRight].w;

	float distX1_Y0 = d_blankTopSurface[bottRight].w;

	float distX0_Y1 = d_blankTopSurface[topLeft].w;

	float value1 = distX0_Y0 + xDelta * (distX1_Y0 - distX0_Y0);

	float value2 = distX0_Y1 + xDelta * (distX1_Y1 - distX0_Y1);

	float ans = (value1 + yDelta * (value2 - value1)); 

	return 1.0;

	//return ans;	

}

In the above function, I would like to return ans. Unfortunately, this doesn’t work. It works when I return a hard coded value like 1.0 as shown.

Any help you can offer is greatly appreciated.

Grateful,

Joshua

2

Either [font=“Courier New”]pathPosition[/font] or [font=“Courier New”]d_blankTopSurface[/font] have bogus values, or you produce an out-of-bounds access to [font=“Courier New”]d_blankTopSurface[/font].

If you return a hard-coded value, the compiler will optimize out the memory accesses.

Is it intentional that [font=“Courier New”]d_partTopSurface[/font] is not used anywhere?

3

Tera,

Thanks for your reply. It was not intentional meant for that to be

d_partTopSurface

instead of

d_blankTopSurface

and this is why I was getting the problem. The reason, it was going as far as it did was because both variables are defined within the global scope. Sometimes you just need fresh eyes…

Grateful,

Joshua