From caddb8b65e1d4fc6cef378d663862d627cd76501 Mon Sep 17 00:00:00 2001
From: Giovanni Bussi <giovanni.bussi@gmail.com>
Date: Tue, 10 Apr 2018 13:22:55 +0200
Subject: [PATCH] Optimized CUSTOM switching function
---
src/tools/SwitchingFunction.cpp | 41 ++++++++++++++++++++++++---------
src/tools/SwitchingFunction.h | 2 ++
2 files changed, 32 insertions(+), 11 deletions(-)
diff --git a/src/tools/SwitchingFunction.cpp b/src/tools/SwitchingFunction.cpp
index 0428be4f2..9616320da 100644
--- a/src/tools/SwitchingFunction.cpp
+++ b/src/tools/SwitchingFunction.cpp
@@ -124,19 +124,22 @@ s(r) = 1 - \tanh\left( \frac{ r - d_0 }{ r_0 } \right)
{TANH R_0=\f$r_0\f$ D_0=\f$d_0\f$}
</td> <td> </td>
</tr> <tr>
-<td> MATHEVAL </td> <td>
+<td> CUSTOM </td> <td>
\f$
s(r) = FUNC
\f$
</td> <td>
-{MATHEVAL FUNC=1/(1+x^6) R_0=\f$r_0\f$ D_0=\f$d_0\f$}
+{CUSTOM FUNC=1/(1+x^6) R_0=\f$r_0\f$ D_0=\f$d_0\f$}
</td> <td> </td>
</tr>
</table>
+Notice that for backward compatibility we allow using `MATHEVAL` instead of `CUSTOM`.
+
\attention
-Notice that using MATHEVAL is much slower than using e.g. RATIONAL.
-Thus, the MATHEVAL switching function is useful to perform quick
+Notice that CUSTOM is slower than other functions
+(e.g., it is slower than an equivalent RATIONAL function by approximately a factor 2).
+Thus, the CUSTOM switching function is useful to perform quick
tests on switching functions with arbitrary form before proceeding to their
implementation in C++.
@@ -254,9 +257,30 @@ void SwitchingFunction::set(const std::string & definition,std::string& errormsg
lepton_func=func;
expression.resize(OpenMP::getNumThreads());
for(auto & e : expression) e=pe.createCompiledExpression();
+ lepton_ref.resize(expression.size());
+ for(unsigned t=0; t<lepton_ref.size(); t++) {
+ try {
+ lepton_ref[t]=&const_cast<lepton::CompiledExpression*>(&expression[t])->getVariableReference("x");
+ } catch(PLMD::lepton::Exception& exc) {
+// this is necessary since in some cases lepton things a variable is not present even though it is present
+// e.g. func=0*x
+ lepton_ref[t]=nullptr;
+ }
+ }
lepton::ParsedExpression ped=lepton::Parser::parse(func).differentiate("x").optimize(leptonConstants);
expression_deriv.resize(OpenMP::getNumThreads());
for(auto & e : expression_deriv) e=ped.createCompiledExpression();
+ lepton_ref_deriv.resize(expression_deriv.size());
+ for(unsigned t=0; t<lepton_ref_deriv.size(); t++) {
+ try {
+ lepton_ref_deriv[t]=&const_cast<lepton::CompiledExpression*>(&expression_deriv[t])->getVariableReference("x");
+ } catch(PLMD::lepton::Exception& exc) {
+// this is necessary since in some cases lepton things a variable is not present even though it is present
+// e.g. func=3*x
+ lepton_ref_deriv[t]=nullptr;
+ }
+ }
+
}
else errormsg="cannot understand switching function type '"+name+"'";
if( !data.empty() ) {
@@ -398,13 +422,8 @@ double SwitchingFunction::calculate(double distance,double&dfunc)const {
} else if(type==leptontype) {
const unsigned t=OpenMP::getThreadNum();
plumed_assert(t<expression.size());
- try {
- const_cast<lepton::CompiledExpression*>(&expression[t])->getVariableReference("x")=rdist;
- const_cast<lepton::CompiledExpression*>(&expression_deriv[t])->getVariableReference("x")=rdist;
- } catch(PLMD::lepton::Exception& exc) {
-// this is necessary since in some cases lepton things a variable is not present even though it is present
-// e.g. func=0*x
- }
+ if(lepton_ref[t]) *lepton_ref[t]=rdist;
+ if(lepton_ref_deriv[t]) *lepton_ref_deriv[t]=rdist;
result=expression[t].evaluate();
dfunc=expression_deriv[t].evaluate();
} else plumed_merror("Unknown switching function type");
diff --git a/src/tools/SwitchingFunction.h b/src/tools/SwitchingFunction.h
index bcb04ad8f..ef4390be3 100644
--- a/src/tools/SwitchingFunction.h
+++ b/src/tools/SwitchingFunction.h
@@ -81,6 +81,8 @@ class SwitchingFunction {
/// Lepton expression for derivative
/// \warning Since lepton::CompiledExpression is mutable, a vector is necessary for multithreading!
std::vector<lepton::CompiledExpression> expression_deriv;
+ std::vector<double*> lepton_ref;
+ std::vector<double*> lepton_ref_deriv;
public:
static void registerKeywords( Keywords& keys );
/// Set a "rational" switching function.
--
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