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Compare NEMO freestream mass fractions against a roundoff tolerance #2880

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Merged
pcarruscag merged 3 commits into from
Sep 7, 2026
+29 −8
Merged

Compare NEMO freestream mass fractions against a roundoff tolerance #2880

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9abcce5
Compare NEMO freestream mass fractions against a roundoff tolerance
bellonarts Sep 3, 2026
e0395aa
Address review: remove broad unit test and add author
bellonarts Sep 5, 2026
54b46ba
Use BlueChips contributor attribution
Sep 5, 2026
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1 change: 1 addition & 0 deletions AUTHORS.md
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Original file line number Diff line number Diff line change
Expand Up @@ -60,6 +60,7 @@ Arne Voß
Ayush Kumar
Beckett Y. Zhou
Benjamin S. Kirk
BlueChips
Brendan Tracey
Brian Munguía
Carsten Othmer
Expand Down
36 changes: 28 additions & 8 deletions SU2_CFD/src/fluid/CSU2TCLib.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,26 @@
#include "../../include/fluid/CSU2TCLib.hpp"
#include "../../../Common/include/option_structure.hpp"

#include <iomanip>
#include <sstream>

/*--- Freestream mass fractions are supplied by the user as decimal literals and
accumulated in double precision, so a physically exact composition need not
sum to bit-exact unity (e.g. 0.999 + 4*0.00025 sums to 1 - 1.1e-16). Compare
against a roundoff tolerance instead: tight enough that any real typo is
still rejected, loose enough that valid input never is. ---*/
constexpr passivedouble MASSFRAC_SUM_TOL = 1.0E-10;

/*--- Report the offending sum with enough digits to tell it apart from unity;
the default six decimals of to_string would print 1.000000 for a sum that
fails the tolerance by less than 5e-7. ---*/
static string MassFracSumErrorMessage(su2double mf) {
ostringstream msg;
msg << "CONFIG ERROR: Initial gas mass fractions do not sum to 1 (sum = " << setprecision(16)
<< SU2_TYPE::GetValue(mf) << ")";
return msg.str();
}

CSU2TCLib::CSU2TCLib(const CConfig* config, unsigned short val_nDim, bool viscous): CNEMOGas(config, val_nDim){

unsigned short maxEl = 0;
Expand Down Expand Up @@ -66,8 +86,8 @@ CSU2TCLib::CSU2TCLib(const CConfig* config, unsigned short val_nDim, bool viscou
mf = 0.0;
for (iSpecies = 0; iSpecies < nSpecies; iSpecies++)
mf += MassFrac_Freestream[iSpecies];
if (mf != 1.0) {
SU2_MPI::Error("CONFIG ERROR: Intial gas mass fractions do not sum to 1!", CURRENT_FUNCTION);
if (fabs(mf - 1.0) > MASSFRAC_SUM_TOL) {
SU2_MPI::Error(MassFracSumErrorMessage(mf), CURRENT_FUNCTION);
}

/*--- Define parameters of the gas model ---*/
Expand Down Expand Up @@ -133,8 +153,8 @@ CSU2TCLib::CSU2TCLib(const CConfig* config, unsigned short val_nDim, bool viscou
mf = 0.0;
for (iSpecies = 0; iSpecies < nSpecies; iSpecies++)
mf += MassFrac_Freestream[iSpecies];
if (mf != 1.0) {
SU2_MPI::Error("CONFIG ERROR: Intial gas mass fractions do not sum to 1!", CURRENT_FUNCTION);
if (fabs(mf - 1.0) > MASSFRAC_SUM_TOL) {
SU2_MPI::Error(MassFracSumErrorMessage(mf), CURRENT_FUNCTION);
}

/*--- Define parameters of the gas model ---*/
Expand Down Expand Up @@ -296,8 +316,8 @@ CSU2TCLib::CSU2TCLib(const CConfig* config, unsigned short val_nDim, bool viscou
mf = 0.0;
for (iSpecies = 0; iSpecies < nSpecies; iSpecies++)
mf += MassFrac_Freestream[iSpecies];
if (mf != 1.0) {
SU2_MPI::Error("CONFIG ERROR: Intial gas mass fractions do not sum to 1!", CURRENT_FUNCTION);
if (fabs(mf - 1.0) > MASSFRAC_SUM_TOL) {
SU2_MPI::Error(MassFracSumErrorMessage(mf), CURRENT_FUNCTION);
}

/*--- Define parameters of the gas model ---*/
Expand Down Expand Up @@ -663,8 +683,8 @@ CSU2TCLib::CSU2TCLib(const CConfig* config, unsigned short val_nDim, bool viscou
mf = 0.0;
for (iSpecies = 0; iSpecies < nSpecies; iSpecies++)
mf += MassFrac_Freestream[iSpecies];
if (mf != 1.0) {
SU2_MPI::Error("CONFIG ERROR: Intial gas mass fractions do not sum to 1!", CURRENT_FUNCTION);
if (fabs(mf - 1.0) > MASSFRAC_SUM_TOL) {
SU2_MPI::Error(MassFracSumErrorMessage(mf), CURRENT_FUNCTION);
}

/*--- Define parameters of the gas model ---*/
Expand Down