id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
4957	Inefficient code generated for record derivatives	Per Östlund	Lennart Ochel	"The backend generates very inefficent code in some cases involving records, for example in {{{ScalableTestSuite.Thermal.Advection.ScaledExperiments.SteamPipe_N_10}}} (and presumably any model using the same parts of Modelica.Media). Looking at the {{{omc_$DER$Modelica$PMedia$PWater$PIF97__Utilities$PwaterBaseProp__ph}}} function in the {{{_functions.c}}} file for example, there's a line in the Modelica code that looks like:
{{{#!mo
 g := Modelica.Media.Water.IF97_Utilities.BaseIF97.Basic.g1(p, aux.T);
}}}
This is translated into the following C-code (line 6213 for me):
{{{#!c
 tmp1 = omc_Modelica_Media_Water_IF97__Utilities_BaseIF97_Basic_g1(threadData, _p, _aux._T);
 _g._p = tmp1._p;
 _g._T = tmp1._T;
 _g._R = tmp1._R;
 _g._pi = tmp1._pi;
 _g._tau = tmp1._tau;
 _g._g = tmp1._g;
 _g._gpi = tmp1._gpi;
 _g._gpipi = tmp1._gpipi;
 _g._gtau = tmp1._gtau;
 _g._gtautau = tmp1._gtautau;
 _g._gtaupi = tmp1._gtaupi;
}}}
Assigning each field of {{{_g}}} separately is a bit weird but might be necessary for all I know, but at least it only calls the functions once. Immediately following this is the following code though (I've shortened the identifiers in the code to make it readable, the actual C-code is much larger):
{{{#!c
 $funDERg._p = omc_$DER$g1(threadData, _p, _aux._T, $funDERp, $funDERaux._T)._p;
 $funDERg._T = omc_$DER$g1(threadData, _p, _aux._T, $funDERp, $funDERaux._T)._T;
 $funDERg._R = omc_$DER$g1(threadData, _p, _aux._T, $funDERp, $funDERaux._T)._R;
 $funDERg._pi = omc_$DER$g1(threadData, _p, _aux._T, $funDERp, $funDERaux._T)._pi;
 $funDERg._tau = omc_$DER$g1(threadData, _p, _aux._T, $funDERp, $funDERaux._T)._tau;
 $funDERg._g = omc_$DER$g1(threadData, _p, _aux._T, $funDERp, $funDERaux._T)._g;
 $funDERg._gpi = omc_$DER$g1(threadData, _p, _aux._T, $funDERp, $funDERaux._T)._gpi;
 $funDERg._gpipi = omc_$DER$g1(threadData, _p, _aux._T, $funDERp, $funDERaux._T)._gpipi;
 $funDERg._gtau = omc_$DER$g1(threadData, _p, _aux._T, $funDERp, $funDERaux._T)._gtau;
 $funDERg._gtautau = omc_$DER$g1(threadData, _p, _aux._T, $funDERp, $funDERaux._T)._gtautau;
 $funDERg._gtaupi = omc_$DER$g1(threadData, _p, _aux._T, $funDERp, $funDERaux._T)._gtaupi;
}}}
It seems like this is calculating some kind of derivative of {{{g}}}, but it does so by calling the {{{omc_$DER$g1}}} function once for each record field. This pattern is repeated all over the generated code, causing a huge amount of unnecessary function calls. And at least {{{g1}}} is quite large and expensive to call, so optimizing this to only call the function once would probably improve the simulation performance quite a bit for models like this."	defect	new	critical	Future	Code Generation	v1.13.0-dev-nightly			Willi Braun