src/gromacs/awh/correlationgrid.cpp

   1 /*
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   5  * Mark Abraham, David van der Spoel, Berk Hess, and Erik Lindahl,
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  35
  36 /*! \internal \file
  37  * \brief
  38  * Implements the CorrelationGrid class to collect correlation statistics on a grid, using several block lengths.
  39  *
  40  * \author Viveca Lindahl
  41  * \author Berk Hess <hess@kth.se>
  42  * \ingroup module_awh
  43  */
  44
  45 #include "gmxpre.h"
  46
  47 #include "correlationgrid.h"
  48
  49 #include "gromacs/math/utilities.h"
  50 #include "gromacs/utility/gmxassert.h"
  51
  52 namespace gmx
  53 {
  54
  55 namespace
  56 {
  57
  58 /*! \brief
  59  * Return the number of block data structs needed for keeping a certain number of blocks.
  60  *
  61  * The list start with 1 block and doubles, so we need 1 + 2log(numBlocks).
  62  *
  63  * \param[in] numBlocks  Number of blocks.
  64  * \returns the number of block data structs.
  65  */
  66 int getBlockDataListSize(int numBlocks)
  67 {
  68     int blockDataListSize = 1;
  69
  70     while (numBlocks > (1 << (blockDataListSize - 1)))
  71     {
  72         blockDataListSize++;
  73     }
  74
  75     GMX_RELEASE_ASSERT((1 << (blockDataListSize - 1)) == numBlocks, "numBlocks should be a power of 2");
  76
  77     return blockDataListSize;
  78 }
  79
  80 }   // namespace
  81
  82 CorrelationGrid::CorrelationGrid(int                numPoints,
  83                                  int                numDim,
  84                                  double             blockLengthInit,
  85                                  BlockLengthMeasure blockLengthMeasure,
  86                                  double             dtSample) :
  87     dtSample(dtSample),
  88     blockLengthMeasure(blockLengthMeasure)
  89 {
  90     /* Set the initial block length for the block averaging. The length doesn't really matter
  91        after the block length has been doubled a few times, as long as it's set small enough */
  92     if (blockLengthMeasure == BlockLengthMeasure::Weight)
  93     {
  94         blockLengthInit = blockLengthInit > 0 ? blockLengthInit : 1;
  95     }
  96     else
  97     {
  98         blockLengthInit = blockLengthInit > 0 ? blockLengthInit : dtSample;
  99     }
 100
 101     /* Set the number of blocks. The number of blocks determines the current span of the data
 102        and how many different block lengths (nblockdata) we need to keep track of to be able to
 103        increase the block length later */
 104     int numBlocks         = CorrelationTensor::c_numCorrelationBlocks;
 105     int BlockDataListSize = getBlockDataListSize(numBlocks);
 106
 107     tensors_.resize(numPoints, CorrelationTensor(numDim, BlockDataListSize, blockLengthInit));
 108 }
 109
 110 int CorrelationGrid::getNumBlocks() const
 111 {
 112     const auto &blockDataList  = tensors()[0].blockDataList();
 113     double      maxBlockLength = blockDataList.back().blockLength();
 114     double      minBlockLength = blockDataList[0].blockLength();
 115
 116     /* If we have a finite block span we have a constant number of blocks, otherwise we are always adding more blocks (and we don't keep track of the number) */
 117     if (maxBlockLength < GMX_DOUBLE_MAX)
 118     {
 119         return static_cast<int>(maxBlockLength/minBlockLength);
 120     }
 121     else
 122     {
 123         return -1;
 124     }
 125 }
 126
 127 double CorrelationGrid::getBlockLength() const
 128 {
 129     /* Return the  minimum blocklength */
 130     return tensors()[0].blockDataList()[0].blockLength();
 131 }
 132
 133 } // namespace gmx