How can I impliment this function in Thrust?
for (i=0;i<n;i++)
if (i==pos)
h1[i]=1/h1[i];
else
开发者_运维技巧 h1[i]=-h1[i]/value;
In CUDA I did it like:
__global__ void inverse_1(double* h1, double value, int pos, int N)
{
int i = blockDim.x * blockIdx.x + threadIdx.x;
if (i < N){
if (i == pos)
h1[i] = 1 / h1[i];
else
h1[i] = -h1[i] / value;
}
}
Thanks!
You need to create a binary functor to apply the operation, then use a counting iterator as the second input. You can pass pos
and value
into the functor's constructor. It'd look something like:
struct inv1_functor
{
const int pos;
const double value;
inv1_functor(double _value, int _pos) : value(_value), pos(_pos) {}
__host__ __device__
double operator()(const double &x, const int &i) const {
if (i == pos)
return 1.0/x;
else
return -x/value;
}
};
//...
thrust::transform(d_vec.begin(), d_vec.end(), thrust::counting_iterator<int>(), d_vec.begin(), inv1_functor(value, pos));
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