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Rewrote function finding interpolation data

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babrodtk
2015-08-19 12:37:54 +02:00
parent 62c2373a9d
commit f3553313d2
3 changed files with 55 additions and 24 deletions
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48
opm/autodiff/VFPHelpers.hpp
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@@ -203,12 +203,15 @@ struct InterpData {
/**
* Helper function to find indices etc. for linear interpolation
* Helper function to find indices etc. for linear interpolation and extrapolation
* @param value Value to find in values
* @param values Sorted list of values to search for value in.
* @return Data required to find the interpolated value
*/
inline InterpData findInterpData(const double& value, const std::vector<double>& values) {
InterpData retval;
const double abs_value = value;//std::abs(value);
const int nvalues = values.size();
//If we only have one value in our vector, return that
if (values.size() == 1) {
@@ -219,25 +222,36 @@ inline InterpData findInterpData(const double& value, const std::vector<double>&
}
// Else search in the vector
else {
//First element greater than or equal to value
//Start with the second element, so that floor_iter does not go out of range
//Don't access out-of-range, therefore values.end()-1
auto ceil_iter = std::lower_bound(values.begin()+1, values.end()-1, abs_value);
//If value is less than all values, use first interval
if (value < values.front()) {
retval.ind_[0] = 0;
retval.ind_[1] = 1;
}
//If value is greater than all values, use last interval
else if (value >= values.back()) {
retval.ind_[0] = nvalues-2;
retval.ind_[1] = nvalues-1;
}
else {
//Search internal intervals
for (int i=1; i<nvalues; ++i) {
if (values[i] >= value) {
retval.ind_[0] = i-1;
retval.ind_[1] = i;
break;
}
}
}
//Find last element smaller than range
auto floor_iter = ceil_iter-1;
//Find the indices
retval.ind_[0] = floor_iter - values.begin();
retval.ind_[1] = ceil_iter - values.begin();
const double start = values[retval.ind_[0]];
const double end = values[retval.ind_[1]];
//Find interpolation ratio
double dist = (*ceil_iter - *floor_iter);
if (std::abs(dist) > 0.0) {
//Possible source for floating point error here if value and floor are large,
if (end > start) {
//FIXME: Possible source for floating point error here if value and floor are large,
//but very close to each other
retval.inv_dist_ = 1.0 / dist;
retval.factor_ = (abs_value-*floor_iter) * retval.inv_dist_;
retval.inv_dist_ = 1.0 / (end-start);
retval.factor_ = (value-start) * retval.inv_dist_;
}
else {
retval.inv_dist_ = 0.0;