Crap values to const param after running kernel

jordyvaneijk · November 23, 2007, 10:18am

Hi again,

I have some strange things happening in my kernel.

this is my kernel call:

calculate_parametric_sets<<<dimGrid, dimBlock>>>(

                    d_alpha_x,

                    d_delta_x,

                    h_dx,

                    d_i_min,

                    d_i_max,

                    d_offset_x,

                    h_xsource, h_x_plane,

                    dimGrid.y,

                    blockSize_x, blockSize_y, block_offset_x, block_offset_y

                    );

this is the kernel header:

__global__ void calculate_parametric_sets( 

          float *alpha,

          const float *delta,

          const float d,

          const int *index_min,

          const int *index_max,

          const unsigned int *prefix_sum,

          const float source, const float plane,

          int gridY, 

          unsigned int blockSize_x, unsigned int blockSize_y, unsigned int offset_x, unsigned int offset_y

          )

So you can see *delta is a constant array of floats. The thing is when I run this my kernel

// set blockindex

  int bx = blockIdx.x;

  int by = blockIdx.y;

  

  // set threadindex	

  int tx = threadIdx.x;

  int ty = threadIdx.y;

	

  // determine x, y and z pending on threadindex and blocksize

  int i = (tx+offset_x) + (bx % gridY) * blockSize_x; // offset is used to tell which subblock will be calculated

  int j = (ty+offset_y) + by * blockSize_y;

  int k = floorf(bx / gridY);

	

  // determine index of voxel

  int index = i + (nx-1)*(j + k *(ny-1));

	

	float d_inv_delta;

	

	float l_delta;

	

	// ends here

	l_delta = delta[index];

	d_inv_delta = d / l_delta;

	

	

	if(l_delta > 0){

  int pos = prefix_sum[index];

  float temp_alpha;

  

  temp_alpha = (plane + (index_min[index] - 1)*d-source) / l_delta;

  alpha[pos] = temp_alpha;

  

  for(int i=1; i<(index_max[index]-index_min[index]); i++) {

  	temp_alpha = temp_alpha + d_inv_delta;

  	alpha[pos+i] = temp_alpha; 

  }	

	}	else {

	

	//VANAF HIER GAAT HET MIS! vervang is 0 door prefix_sum[index] dan krijg ik allemaal vreemde delta waardes.

  int pos = 0;//prefix_sum[index];

  float temp_alpha;

  

  temp_alpha = (plane + (index_max[index] - 1)*d-source) / l_delta; 

  alpha[pos] = temp_alpha;

  

  for(int i=1; i<index_max[index]-index_min[index]; i++) {

  	temp_alpha = temp_alpha + d_inv_delta;

  	alpha[pos+i] = temp_alpha;

  }

	}	

	

}

in the if part it all goes fine but when i come to the else part and change the int pos = 0; to int pos = prefix_sum[index] the values of delta will be rubbish

good values:

Delta X values

-21.375000  -19.125000  -16.875000  -14.625000  -12.375000  -10.125000  -7.875000  -5.625000  -3.375000  -1.125000  1.125000  3.375000  5.625000  7.875000  10.125000  12.375000  

-21.375000  -19.125000  -16.875000  -14.625000  -12.375000  -10.125000  -7.875000  -5.625000  -3.375000  -1.125000  1.125000  3.375000  5.625000  7.875000  10.125000  12.375000  

-21.375000  -19.125000  -16.875000  -14.625000  -12.375000  -10.125000  -7.875000  -5.625000  -3.375000  -1.125000  1.125000  3.375000  5.625000  7.875000  10.125000  12.375000  

-21.375000  -19.125000  -16.875000  -14.625000  -12.375000  -10.125000  -7.875000  -5.625000  -3.375000  -1.125000  1.125000  3.375000  5.625000  7.875000  10.125000  12.375000  

-21.375000  -19.125000  -16.875000  -14.625000  -12.375000  -10.125000  -7.875000  -5.625000  -3.375000  -1.125000  1.125000  3.375000  5.625000  7.875000  10.125000  12.375000  

-21.375000  -19.125000  -16.875000  -14.625000  -12.375000  -10.125000  -7.875000  -5.625000  -3.375000  -1.125000  1.125000  3.375000  5.625000  7.875000  10.125000  12.375000  

-21.375000  -19.125000  -16.875000  -14.625000  -12.375000  -10.125000  -7.875000  -5.625000  -3.375000  -1.125000  1.125000  3.375000  5.625000  7.875000  10.125000  12.375000  

-21.375000  -19.125000  -16.875000  -14.625000  -12.375000  -10.125000  -7.875000  -5.625000  -3.375000  -1.125000  1.125000  3.375000  5.625000  7.875000  10.125000  12.375000  

-21.375000  -19.125000  -16.875000  -14.625000  -12.375000  -10.125000  -7.875000  -5.625000  -3.375000  -1.125000  1.125000  3.375000  5.625000  7.875000  10.125000  12.375000  

-21.375000  -19.125000  -16.875000  -14.625000  -12.375000  -10.125000  -7.875000  -5.625000  -3.375000  -1.125000  1.125000  3.375000  5.625000  7.875000  10.125000  12.375000  

-21.375000  -19.125000  -16.875000  -14.625000  -12.375000  -10.125000  -7.875000  -5.625000  -3.375000  -1.125000  1.125000  3.375000  5.625000  7.875000  10.125000  12.375000  

-21.375000  -19.125000  -16.875000  -14.625000  -12.375000  -10.125000  -7.875000  -5.625000  -3.375000  -1.125000  1.125000  3.375000  5.625000  7.875000  10.125000  12.375000  

-21.375000  -19.125000  -16.875000  -14.625000  -12.375000  -10.125000  -7.875000  -5.625000  -3.375000  -1.125000  1.125000  3.375000  5.625000  7.875000  10.125000  12.375000  

-21.375000  -19.125000  -16.875000  -14.625000  -12.375000  -10.125000  -7.875000  -5.625000  -3.375000  -1.125000  1.125000  3.375000  5.625000  7.875000  10.125000  12.375000  

-21.375000  -19.125000  -16.875000  -14.625000  -12.375000  -10.125000  -7.875000  -5.625000  -3.375000  -1.125000  1.125000  3.375000  5.625000  7.875000  10.125000  12.375000  

-21.375000  -19.125000  -16.875000  -14.625000  -12.375000  -10.125000  -7.875000  -5.625000  -3.375000  -1.125000  1.125000  3.375000  5.625000  7.875000  10.125000  12.375000

bad values:

Delta X values

0.000000  0.000000  0.000000  14281679716281643063034706579685376.000000  0.000000  0.000000  0.000000  0.000000  0.000000  0.000000  0.000042  0.000000  0.000000  0.000044  0.000000  0.000000  

0.000000  0.000000  0.000000  0.000014  0.000000  0.000000  0.000000  14289081359776530351698328443420672.000000  0.000000  0.000000  0.000000  0.000000  0.000000  0.000000  0.000000  0.000044  

14289016986894487511924033688961024.000000  0.000000  0.000169  0.000000  0.000000  0.000000  0.000000  0.000000  0.000000  14289028128354841080346507781079040.000000  0.000000  0.000000  0.000000  0.000000  0.000000  0.000000  

0.000014  0.000000  14281679716281643063034706579685376.000000  0.000000  0.000169  0.000000  0.000000  0.000000  0.000000  0.000042  0.000000  0.000000  0.000044  0.000000  0.000004  0.000000  

0.000000  0.000000  0.000014  0.000000  0.000000  0.000000  14289081359776530351698328443420672.000000  0.000000  0.000000  0.000000  0.000000  0.000042  0.000000  0.000000  0.000044  14289016986894487511924033688961024.000000  

0.000000  0.000001  0.000000  0.000000  0.000000  0.000000  0.000000  0.000000  14289018224834526797304308588085248.000000  0.000000  0.000000  0.000000  0.000042  0.000000  0.000000  0.000000  

0.000000  14281679716281643063034706579685376.000000  0.000000  0.000001  0.000000  0.000042  0.000000  0.000000  203131272386593161216.000000  0.000000  0.000000  0.000044  0.000000  0.000000  0.000042  0.000000  

0.000000  0.000000  0.000000  0.000000  0.000000  14289018224834526797304308588085248.000000  0.000000  0.000000  0.000000  0.000000  0.000000  0.000000  0.000000  0.000044  14289016986894487511924033688961024.000000  0.000001  

0.000000  0.000000  0.000000  0.000000  0.000000  0.000000  0.000000  14289020700714605368064858386333696.000000  0.000000  0.000000  293008659327554821292032.000000  0.000000  0.000000  0.000000  0.000000  0.000000  

14281679716281643063034706579685376.000000  0.000000  0.000000  0.000000  0.000000  0.000000  0.000000  0.000000  0.000000  0.000000  0.000044  0.000000  286140864254286233600.000000  0.000000  0.000000  0.000000  

0.000011  0.000000  0.000000  0.000000  14289081359776530351698328443420672.000000  0.000000  0.000000  0.000000  0.000000  0.000003  0.000000  0.000000  0.000044  14289016986894487511924033688961024.000000  0.000000  0.000170  

0.000000  0.000000  0.000000  0.000000  0.000000  0.000000  14289023176594683938825408184582144.000000  0.000000  0.000000  286141268874565255168.000000  0.000000  0.000000  0.000000  0.000011  0.000000  14281679716281643063034706579685376.000000  

0.000011  0.000169  0.000000  0.000000  0.000000  0.000000  0.000003  0.000000  0.000000  0.000044  0.000000  0.000000  0.000000  0.000000  0.000000  0.000011  

0.000000  0.000000  0.000000  14289028128354841080346507781079040.000000  0.000000  0.000000  0.000000  0.000000  3250747750631925088256.000000  0.000000  0.000000  3379226722276527308800.000000  14289016986894487511924033688961024.000000  0.000000  13149700263988921630720.000000  0.000000  

0.000042  0.000000  0.000000  0.000000  0.000000  14289028128354841080346507781079040.000000  0.000000  0.000000  0.000000  0.000000  0.000000  0.000000  0.000011  0.000000  14281679716281643063034706579685376.000000  0.000042  

0.000169  4578260301993044082688.000000  0.000000  0.000000  0.000000  0.000000  0.000000  0.000000  0.000000  0.000000  18313015312274318950400.000000  0.000000  0.000000  0.000000  0.000011  0.000000

It looks like I’m calling some part of the memory which is not the original d_delta_x but I don’t know exactly.

I hope some1 can help me.

Thanks Jordy

MisterAnderson42 · November 23, 2007, 2:56pm

Have you tried stepping through this kernel in the debugger in emulation mode? Putting watches on the variables and stepping line by line through the else should help you spot the problem.

jordyvaneijk · November 27, 2007, 8:43am

Well the problem is this. I’m using the parallel prefix sum and if i use emulation mode. My parallel prefix sum always gets 0.

So now I’m wondering how I can fix this problem.

BTW I’m using CUDA 1.0

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Crap values to const param after running kernel

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