dll inconsistent response

[hugo-cwp]

Description

When running RP.SETFLUIDSdll and RP.REFPROPdll I occasionally receive a -101 error. I resolved repeating the query for that case alone, which solves the issue (I have never received -101 twice in a row).

I am unsure about the reason for the error. At any rate it should not fail once and then work, in my opinion. Details below.

Workaround for RP.SETFLUIDSdll:

import os
from ctREFPROP.ctREFPROP import REFPROPFunctionLibrary,get_default_DLL_extension,REFPROPInstance

RP_PATH = os.path.join(os.path.dirname(__file__), '..','resources','REFPROP')
extension=get_default_DLL_extension()
RP = REFPROPFunctionLibrary(RP_PATH,extension)
RP.SETPATHdll(RP_PATH)

loaded_fluids=[]

def check_fluid(fluid:str):
    fluid=fluid.upper()
    global loaded_fluids
    if fluid is None:
        raise ValueError('❌ No fluid specified')
    if fluid not in loaded_fluids:
        # check if fluid is known
        ierr=RP.SETFLUIDSdll(fluid.upper())
        if ierr != 0:
            if ierr == -101: # try again. For some reason trying twice does the trick
                ierr=RP.SETFLUIDSdll(fluid.upper())
            if ierr != 0:
                # throw error
                errmsg=RP.ERRMSGdll(ierr)
                raise ValueError(f'❌ Fluid {fluid} not found in REFPROP FLD files. Error code: {ierr}: {errmsg}')
        else:
            loaded_fluids.append(fluid)
            print(f'✅ Fluid {fluid} loaded in REFPROP')
            return True
    else:
        return True

Workaround for RP.REFPROPdll:

    def get_prop(self,RP_input:str,RP_output:str,a,b,units=0):
        property=0
        hFld=';'.join([key for key in self.species_dict])
        z=[self.species_dict[key] for key in self.species_dict]
        result=refprop_ops.RP.REFPROPdll(hFld,RP_input,RP_output,units,0,0,a,b,z)
        if result.ierr==-101:
            # retry, sometimes REFPROPdll fails
            result=refprop_ops.RP.REFPROPdll(hFld,RP_input,RP_output,units,0,0,a,b,z)

Steps to Reproduce

Use the functions defined above

Expected behavior: ierr = 0 first try

Actual behavior: ierr = 101 --> ierr = 0

Versions

REFPROP Version: 10.0
Operating System and Version: Windows 10.022631 and Linux
Access Method: Python

Additional Information

[ianhbell]

This is a bug in REFPROP. You should receive the same error message the second time too.

[hugo-cwp]

Well I checked again and it's consistently returning -101 then 0. Can I still trust the result of my second query? Thanks

[ianhbell]

No, it is a bug. You should in principle get -101 for the second call too.

[ianhbell]

Can you give me an example that gives -101 for the error code? I can't reproduce on my side