Overview

Computes base 2 log of input vector and stores results in output vector.

Note that this implementation is not conforming to the IEEE FP standard, i.e., +-Inf outputs are mapped to +-127.0f and +-NaN input values are not supported.

This kernel was adapted from Jose Fonseca's Fast SSE2 log implementation http://jrfonseca.blogspot.in/2008/09/fast-sse2-pow-tables-or-polynomials.htm

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sub license, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice (including the next paragraph) shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL TUNGSTEN GRAPHICS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

This is the MIT License (MIT)

Dispatcher Prototype

void volk_32f_log2_32f(float* bVector, const float* aVector, unsigned int num_points)

Inputs

• aVector: the input vector of floats.
• num_points: The number of data points.

Outputs

• bVector: The output vector.

Example

int N = 10;
unsigned int alignment = volk_get_alignment();
float* in = (float*)volk_malloc(sizeof(float)*N, alignment);
float* out = (float*)volk_malloc(sizeof(float)*N, alignment);
 
for(unsigned int ii = 0; ii < N; ++ii){
    in[ii] = std::pow(2.f,((float)ii));
}
 
volk_32f_log2_32f(out, in, N);
 
for(unsigned int ii = 0; ii < N; ++ii){
    printf("out(%i) = %f\n", ii, out[ii]);
}
 
volk_free(in);
volk_free(out);