I lost data after __syncthreads() in cuda - cuda

Question

I am trying to find the maximum of an array.. I took the help from CUDA Maximum Reduction Algorithm Not Working. and do some own modification. However I am running it for 16 data. I am finding that in kernel code shared memory copies only 1st 4data. rest are lost. I put two cuPrintf..1st printf shows data is their in the shared memory. But the 2nd cuPrintf is just after __syncthreads.. and that shows 0 from thread ids 4 onwords.. pls help
#include
#include
#include
#include
#include
#include "cuPrintf.cu"
#include "cuPrintf.cuh"
__device__ float MaxOf2(float a, float b)
{
if(a > b) return a;
else return b;
}
__global__ void findMax(int size,float *array_device , float *outPut)
{
extern __shared__ float sdata[];
int tid = threadIdx.x;
int i = blockIdx.x*blockDim.x + threadIdx.x;
if(i< size)
{
sdata[tid] = array_device[i];
cuPrintf(" array_d[%d]===%f, sdata[%d]===%f\n ",i,array_device[i],tid,sdata[tid]);
__threadfence();
}
__syncthreads();
if(tid<size)
cuPrintf(" array_d[%d]===%f, sdata[%d]===%f\n ",i,array_device[i],tid,sdata[tid]);
for ( int s=blockDim.x/2; s>0; s=s>>1)//s=blockDim.x/2
{
if (tid < s)
{
sdata[tid]= MaxOf2(sdata[tid],sdata[tid+s]);
}
__syncthreads();
}
if (tid == 0) outPut[blockIdx.x] = sdata[0];
}
int main()
{
long double M = pow(2,20);
long double N = 2;
int noThreadsPerBlock = 512 ;
printf("\n Provide the array Size N.(array will be of size N * 2^20 ) :-");
scanf("%Lf",&N);
long int size = 16;
int numOfBlock = (int)size /noThreadsPerBlock + 1;
printf("\n num of blocks==%ld",numOfBlock);
float *array_device , *outPut;
float array_host[]={221,100,2,340,47,36,500,1,33,4460,5,6,7,8,9,11};
cudaMalloc((void **)&array_device, size*sizeof(float));
cudaMalloc((void **)&outPut, size*sizeof(float));
cudaError_t error0 = cudaGetLastError();
printf("\n 0CUDA error: %s\n", cudaGetErrorString(error0));
printf("size===%ld",size);
cudaMemcpy(array_device, array_host, size*sizeof(float), cudaMemcpyHostToDevice);
cudaError_t error1 = cudaGetLastError();
printf("\n1CUDA error: %s\n", cudaGetErrorString(error1));
while(size>1 )
{
cudaPrintfInit();
findMax<<< numOfBlock,noThreadsPerBlock>>>(size,array_device, outPut);cudaPrintfDisplay(stdout, true);
cudaPrintfEnd();
cudaError_t error2 = cudaGetLastError();
printf(" 2CUDA error: %s\n", cudaGetErrorString(error2));
cudaMemcpy(array_device, outPut, size*sizeof(float), cudaMemcpyDeviceToDevice);
size = numOfBlock;
printf("\n ****size==%ld\n",size);
numOfBlock = (int)size /noThreadsPerBlock + 1;
}
cudaMemcpy(array_host, outPut, size*sizeof(float), cudaMemcpyDeviceToHost);
cudaError_t error3 = cudaGetLastError();
printf("\n3CUDA error: %s\n", cudaGetErrorString(error3));
for(int i=0;i<size;i++)
printf("\n index==%d ;data=%f ",i,array_host[i]);
return 0;
}

Answer 1

I'm posting my comment as an answer as requested.
Firstly, you havent specified dynamic size of shared memory in kernel launch. It should look something like:
findMax<<< numOfBlock,noThreadsPerBlock,sizeof(float)*noThreadsPerBlock>>>
Secondly, what was the concept behind condition if(tid<size) on second cuPrintf? Providing output of the program could also help.