Overview

Returns Argmax_i mag(x[i]). Finds and returns the index which contains the maximum magnitude for complex points in the given vector.

Note that num_points is a uint32_t, but the return value is uint16_t. Providing a vector larger than the max of a uint16_t (65536) would miss anything outside of this boundary. The kernel will check the length of num_points and cap it to this max value, anyways.

Dispatcher Prototype

void volk_32fc_index_max_16u(uint16_t* target, lv_32fc_t* src0, uint32_t
num_points) 

Inputs

• src0: The complex input vector.
• num_points: The number of samples.

Outputs

• target: The index of the point with maximum magnitude.

Example Calculate the index of the maximum value of for points around the unit circle.

int N = 10;
uint32_t alignment = volk_get_alignment();
lv_32fc_t* in  = (lv_32fc_t*)volk_malloc(sizeof(lv_32fc_t)*N, alignment);
uint16_t* max = (uint16_t*)volk_malloc(sizeof(uint16_t), alignment);
 
for(uint32_t ii = 0; ii < N/2; ++ii){
    float real = 2.f * ((float)ii / (float)N) - 1.f;
    float imag = std::sqrt(1.f - real * real);
    in[ii] = lv_cmake(real, imag);
    in[ii] = in[ii] * in[ii] + in[ii];
    in[N-ii] = lv_cmake(real, imag);
    in[N-ii] = in[N-ii] * in[N-ii] + in[N-ii];
}
 
volk_32fc_index_max_16u(max, in, N);
 
printf("index of max value = %u\n",  *max);
 
volk_free(in);
volk_free(max);