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86 lines
3.5 KiB
C
86 lines
3.5 KiB
C
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// pdmath.h
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// Elementary math on probability distributions
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//
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// (c) 2016 - Nico Palermo, IV3NWV - Microtelecom Srl, Italy
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// ------------------------------------------------------------------------------
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// This file is part of the qracodes project, a Forward Error Control
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// encoding/decoding package based on Q-ary RA (repeat and accumulate) LDPC codes.
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//
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// qracodes is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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// qracodes is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// You should have received a copy of the GNU General Public License
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// along with qracodes source distribution.
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// If not, see <http://www.gnu.org/licenses/>.
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#ifndef _pdmath_h_
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#define _pdmath_h_
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#include <memory.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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#define PD_NDIM(nlogdim) ((1<<(nlogdim))
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#define PD_SIZE(ndim) ((ndim)*sizeof(float))
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#define PD_ROWADDR(fp,ndim,idx) (fp+((ndim)*(idx)))
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const float *pd_uniform(int nlogdim);
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// Returns a pointer to a (constant) uniform distribution of the given log2 size
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#define pd_init(dst,src,ndim) memcpy(dst,src,PD_SIZE(ndim))
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// Distribution copy
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void pd_memset(float *dst, const float *src, int ndim, int nitems);
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// Copy the distribution pointed by src to the array of distributions dst
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// src is a pointer to the input distribution (a vector of size ndim)
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// dst is a pointer to a linear array of distributions (a vector of size ndim*nitems)
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void pd_imul(float *dst, const float *src, int nlogdim);
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// In place multiplication
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// Compute dst = dst*src for any element of the distrib give their log2 size
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// src and dst arguments must be pointers to array of floats of the given size
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float pd_norm(float *pd, int nlogdim);
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// In place normalizazion
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// Normalizes the input vector so that the sum of its components are one
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// pd must be a pointer to an array of floats of the given size.
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// If the norm of the input vector is non-positive the vector components
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// are replaced with a uniform distribution
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// Returns the norm of the distribution prior to the normalization
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void pd_fwdperm(float *dst, float *src, const int *perm, int ndim);
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// Forward permutation of a distribution
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// Computes dst[k] = src[perm[k]] for every element in the distribution
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// perm must be a pointer to an array of integers of length ndim
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void pd_bwdperm(float *dst, float *src, const int *perm, int ndim);
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// Backward permutation of a distribution
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// Computes dst[perm[k]] = src[k] for every element in the distribution
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// perm must be a pointer to an array of integers of length ndim
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float pd_max(float *src, int ndim);
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// Return the maximum of the elements of the given distribution
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// Assumes that the input vector is a probability distribution and that each element in the
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// distribution is non negative
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int pd_argmax(float *pmax, float *src, int ndim);
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// Return the index of the maximum element of the given distribution
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// The maximum is stored in the variable pointed by pmax if pmax is not null
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// Same note of pd_max applies.
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// Return -1 if all the elements in the distribution are negative
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#ifdef __cplusplus
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}
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#endif
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#endif // _pdmath_h_
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