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Actually tell why file read fails #51

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Actually tell why file read fails #51

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4868c08
Actually tell why file read fails
lkotipal Dec 4, 2023
d223d21
Output MPI errors as strings
lkotipal Dec 4, 2023
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14 changes: 9 additions & 5 deletions vlsv_reader_parallel.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -417,7 +417,8 @@ namespace vlsv {
* @param mpiInfo Additional MPI info for optimizing file I/O. Must be the same value on all processes.
* @return If true, VLSV file was opened successfully. All processes return the same value.*/
bool ParallelReader::open(const std::string& fname,MPI_Comm comm,const int& masterRank,MPI_Info mpiInfo) {
bool success = true;
bool success {true};
int error {MPI_SUCCESS};
this->comm = comm;
this->masterRank = masterRank;
MPI_Comm_rank(comm,&myRank);
Expand All @@ -430,10 +431,13 @@ namespace vlsv {
// Attempt to open the given input file using MPI:
fileName = fname;
int accessMode = MPI_MODE_RDONLY;
if (MPI_File_open(comm,const_cast<char*>(fileName.c_str()),accessMode,mpiInfo,&filePtr) != MPI_SUCCESS) success = false;
else parallelFileOpen = true;

if (success == false) cerr << "Failed to open parallel file" << endl;
error = MPI_File_open(comm,const_cast<char*>(fileName.c_str()),accessMode,mpiInfo,&filePtr);
if (error == MPI_SUCCESS) {
parallelFileOpen = true;
} else {
success = false;
cerr << "Failed to open parallel file with MPI error " << error << endl;
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Is this now a number, or some string?

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That's an int. I suppose the proper way would be to have a function mapping error codes to descriptions of MPI errors but now it at least doesn't just gobble up the error code and spit out the non-answer of "there was an error".

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https://www.open-mpi.org/doc/v3.0/man3/MPI_Error_string.3.php

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Yeah that tracks, just needs a whopper to convert that from C-string to something sensible.

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Can't that be plonked to cerr? Or to a stringstreamstream and then that gets cerr'ed?

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@lkotipal lkotipal Dec 4, 2023 •
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Look at the function signature, the actual string "returned" is an argument. So the conversion is sth like:

char c[MPI_MAX_ERROR_STRING];
int len;
MPI_Error_string(err, c, &len);
std::string s (s, len);

}

// Only master process reads file footer and endianness. This is done using
// VLSVReader open() member function:
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