20242, "benharsh", "What should ''on myFile'' do?", "2022-07-18T21:20:11Z"
On-statements like on expr are usually implemented as on expr.locale. Currently the file type stores the locale on which the file was opened, and channels will use on-statements internally when reading/writing from another locale. Currently an expression like on myFile will use myFile.locale rather than myFIle.home, and these two might not be the same.
Consider the following program:
use IO;
use CommDiagnostics;
proc main() {
var myFile : file;
on Locales.last {
myFile = open("someFile.txt", iomode.cw);
}
writeln("myFile.home = ", myFile.home);
writeln("myFile.locale = ", myFile.locale);
writeln();
writeln("'on myFile'");
startCommDiagnostics();
on myFile {
writeln("Writing on: ", here);
var w = myFile.writer();
for i in 1..10 do
w.writeln(i);
}
stopCommDiagnostics();
printCommDiagnosticsTable();
resetCommDiagnostics();
writeln();
writeln("'on myFile.home'");
startCommDiagnostics();
on myFile.home {
writeln("Writing on: ", here);
var w = myFile.writer();
for i in 1..10 do
w.writeln(i);
}
stopCommDiagnostics();
printCommDiagnosticsTable();
}
Running with two locales:
myFile.home = LOCALE1
myFile.locale = LOCALE0
'on myFile'
Writing on: LOCALE0
> locale | get_nb | put_nb | execute_on | cache_get_hits | cache_get_misses | cache_put_hits | cache_put_misses |
> -----: | -----: | -----: | ---------: | -------------: | ---------------: | -------------: | ---------------: |
> 0 | 0 | 0 | 13 | 0 | 0 | 0 | 0 |
> 1 | 15 | 4 | 1 | 15 | 15 | 1 | 4 |
'on myFile.home'
Writing on: LOCALE1
> locale | get_nb | execute_on | cache_get_hits | cache_get_misses |
> -----: | -----: | ---------: | -------------: | ---------------: |
> 0 | 9 | 1 | 5 | 9 |
> 1 | 2 | 1 | 8 | 2 |
We see 13 on-statements in the on myFile case, indicating that we're not executing on the locale where IO writes are actually occurring.
Some relevant questions: