Is continually writing to a file detrimental to the performance of a program?
Imagine a parallel "high performance program" that reads in files, each process performs a task on the input data and then each process writes an output for the task to a single shared output file before repeating this procedure.
In terms of performance, is it inefficient to write the outputs to a file as each process finishes a task?
Would it be more efficient to store the results in an array and write the array to an output file at the end?
c parallel-processing io hpc
asked Nov 22 '18 at 22:17
HCF3301HCF3301
616
add a comment |
Imagine a parallel "high performance program" that reads in files, each process performs a task on the input data and then each process writes an output for the task to a single shared output file before repeating this procedure.
In terms of performance, is it inefficient to write the outputs to a file as each process finishes a task?
Would it be more efficient to store the results in an array and write the array to an output file at the end?
c parallel-processing io hpc
asked Nov 22 '18 at 22:17
HCF3301HCF3301
616
1
You could try creating a MVCE for both scenarios and do some measurements (e. g. use a performance profiler and/or a memory profiler and/or someStopwatchinstances).
– Uwe Keim
Nov 22 '18 at 22:18
Please do not add "Thank you" to questions.
– Uwe Keim
Nov 22 '18 at 22:18
The answer depends on context. It can be either way. Code it both ways and benchmark them to see.
– Craig Estey
Nov 22 '18 at 22:24
If your platform supports memory-mapped files, you don't have to choose.
– EOF
Nov 22 '18 at 23:28
I read the first paragraph and now I'm imagining 65,356 processes each taking its turn to write to the single shared output file. Even with far fewer processes in play this is going to look pretty much like a serial program and it's not a good outline design.
– High Performance Mark
Nov 23 '18 at 8:32
add a comment |
Imagine a parallel "high performance program" that reads in files, each process performs a task on the input data and then each process writes an output for the task to a single shared output file before repeating this procedure.
In terms of performance, is it inefficient to write the outputs to a file as each process finishes a task?
Would it be more efficient to store the results in an array and write the array to an output file at the end?
c parallel-processing io hpc
asked Nov 22 '18 at 22:17
HCF3301HCF3301
616
Imagine a parallel "high performance program" that reads in files, each process performs a task on the input data and then each process writes an output for the task to a single shared output file before repeating this procedure.
In terms of performance, is it inefficient to write the outputs to a file as each process finishes a task?
Would it be more efficient to store the results in an array and write the array to an output file at the end?
c parallel-processing io hpc
c parallel-processing io hpc
asked Nov 22 '18 at 22:17
HCF3301HCF3301
616
asked Nov 22 '18 at 22:17
HCF3301HCF3301
616
edited Nov 22 '18 at 22:39
HCF3301
asked Nov 22 '18 at 22:17
HCF3301HCF3301
616
asked Nov 22 '18 at 22:17
HCF3301HCF3301
616
asked Nov 22 '18 at 22:17
HCF3301HCF3301
616
616
1
You could try creating a MVCE for both scenarios and do some measurements (e. g. use a performance profiler and/or a memory profiler and/or someStopwatchinstances).
– Uwe Keim
Nov 22 '18 at 22:18
Please do not add "Thank you" to questions.
– Uwe Keim
Nov 22 '18 at 22:18
The answer depends on context. It can be either way. Code it both ways and benchmark them to see.
– Craig Estey
Nov 22 '18 at 22:24
If your platform supports memory-mapped files, you don't have to choose.
– EOF
Nov 22 '18 at 23:28
I read the first paragraph and now I'm imagining 65,356 processes each taking its turn to write to the single shared output file. Even with far fewer processes in play this is going to look pretty much like a serial program and it's not a good outline design.
– High Performance Mark
Nov 23 '18 at 8:32
add a comment |
1
You could try creating a MVCE for both scenarios and do some measurements (e. g. use a performance profiler and/or a memory profiler and/or someStopwatchinstances).
– Uwe Keim
Nov 22 '18 at 22:18
Please do not add "Thank you" to questions.
– Uwe Keim
Nov 22 '18 at 22:18
The answer depends on context. It can be either way. Code it both ways and benchmark them to see.
– Craig Estey
Nov 22 '18 at 22:24
If your platform supports memory-mapped files, you don't have to choose.
– EOF
Nov 22 '18 at 23:28
I read the first paragraph and now I'm imagining 65,356 processes each taking its turn to write to the single shared output file. Even with far fewer processes in play this is going to look pretty much like a serial program and it's not a good outline design.
– High Performance Mark
Nov 23 '18 at 8:32
1
1
You could try creating a MVCE for both scenarios and do some measurements (e. g. use a performance profiler and/or a memory profiler and/or some
Stopwatch instances).– Uwe Keim
Nov 22 '18 at 22:18
You could try creating a MVCE for both scenarios and do some measurements (e. g. use a performance profiler and/or a memory profiler and/or some
Stopwatch instances).– Uwe Keim
Nov 22 '18 at 22:18
Please do not add "Thank you" to questions.
– Uwe Keim
Nov 22 '18 at 22:18
Please do not add "Thank you" to questions.
– Uwe Keim
Nov 22 '18 at 22:18
The answer depends on context. It can be either way. Code it both ways and benchmark them to see.
– Craig Estey
Nov 22 '18 at 22:24
The answer depends on context. It can be either way. Code it both ways and benchmark them to see.
– Craig Estey
Nov 22 '18 at 22:24
If your platform supports memory-mapped files, you don't have to choose.
– EOF
Nov 22 '18 at 23:28
If your platform supports memory-mapped files, you don't have to choose.
– EOF
Nov 22 '18 at 23:28
I read the first paragraph and now I'm imagining 65,356 processes each taking its turn to write to the single shared output file. Even with far fewer processes in play this is going to look pretty much like a serial program and it's not a good outline design.
– High Performance Mark
Nov 23 '18 at 8:32
I read the first paragraph and now I'm imagining 65,356 processes each taking its turn to write to the single shared output file. Even with far fewer processes in play this is going to look pretty much like a serial program and it's not a good outline design.
– High Performance Mark
Nov 23 '18 at 8:32
add a comment |
2 Answers
2
active
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This is problem where full IO disk read write has to be exploited without delays from client processes or threads. If Std C library calls are used it uses memory buffer that gets flushed at newline or fflush() call is made. If the data is not big enough using array is efficient that can be written to file at the end so performance demanding task will not suffer IO delays.
answered Nov 23 '18 at 2:43
anandanand
1377
add a comment |
Files are usually slower than RAM. However, how much slower? If it's less than 1% slowdown, most people would not care. If it's 50% slowdown, some people would still not care.
As always with performance, measure it one way and the other, and then decide whether the difference is significant. The decision will usually depend on factors which are highly application-specific.
answered Nov 22 '18 at 22:22
anatolyganatolyg
17k44693
add a comment |
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2 Answers
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active
oldest
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2 Answers
2
active
oldest
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active
oldest
votes
This is problem where full IO disk read write has to be exploited without delays from client processes or threads. If Std C library calls are used it uses memory buffer that gets flushed at newline or fflush() call is made. If the data is not big enough using array is efficient that can be written to file at the end so performance demanding task will not suffer IO delays.
answered Nov 23 '18 at 2:43
anandanand
1377
add a comment |
This is problem where full IO disk read write has to be exploited without delays from client processes or threads. If Std C library calls are used it uses memory buffer that gets flushed at newline or fflush() call is made. If the data is not big enough using array is efficient that can be written to file at the end so performance demanding task will not suffer IO delays.
answered Nov 23 '18 at 2:43
anandanand
1377
add a comment |
This is problem where full IO disk read write has to be exploited without delays from client processes or threads. If Std C library calls are used it uses memory buffer that gets flushed at newline or fflush() call is made. If the data is not big enough using array is efficient that can be written to file at the end so performance demanding task will not suffer IO delays.
answered Nov 23 '18 at 2:43
anandanand
1377
This is problem where full IO disk read write has to be exploited without delays from client processes or threads. If Std C library calls are used it uses memory buffer that gets flushed at newline or fflush() call is made. If the data is not big enough using array is efficient that can be written to file at the end so performance demanding task will not suffer IO delays.
answered Nov 23 '18 at 2:43
anandanand
1377
answered Nov 23 '18 at 2:43
anandanand
1377
answered Nov 23 '18 at 2:43
anandanand
1377
answered Nov 23 '18 at 2:43
anandanand
1377
1377
add a comment |
add a comment |
Files are usually slower than RAM. However, how much slower? If it's less than 1% slowdown, most people would not care. If it's 50% slowdown, some people would still not care.
As always with performance, measure it one way and the other, and then decide whether the difference is significant. The decision will usually depend on factors which are highly application-specific.
answered Nov 22 '18 at 22:22
anatolyganatolyg
17k44693
add a comment |
Files are usually slower than RAM. However, how much slower? If it's less than 1% slowdown, most people would not care. If it's 50% slowdown, some people would still not care.
As always with performance, measure it one way and the other, and then decide whether the difference is significant. The decision will usually depend on factors which are highly application-specific.
answered Nov 22 '18 at 22:22
anatolyganatolyg
17k44693
add a comment |
Files are usually slower than RAM. However, how much slower? If it's less than 1% slowdown, most people would not care. If it's 50% slowdown, some people would still not care.
As always with performance, measure it one way and the other, and then decide whether the difference is significant. The decision will usually depend on factors which are highly application-specific.
answered Nov 22 '18 at 22:22
anatolyganatolyg
17k44693
Files are usually slower than RAM. However, how much slower? If it's less than 1% slowdown, most people would not care. If it's 50% slowdown, some people would still not care.
As always with performance, measure it one way and the other, and then decide whether the difference is significant. The decision will usually depend on factors which are highly application-specific.
answered Nov 22 '18 at 22:22
anatolyganatolyg
17k44693
answered Nov 22 '18 at 22:22
anatolyganatolyg
17k44693
answered Nov 22 '18 at 22:22
anatolyganatolyg
17k44693
answered Nov 22 '18 at 22:22
anatolyganatolyg
17k44693
17k44693
add a comment |
add a comment |
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1
You could try creating a MVCE for both scenarios and do some measurements (e. g. use a performance profiler and/or a memory profiler and/or some
Stopwatchinstances).– Uwe Keim
Nov 22 '18 at 22:18
Please do not add "Thank you" to questions.
– Uwe Keim
Nov 22 '18 at 22:18
The answer depends on context. It can be either way. Code it both ways and benchmark them to see.
– Craig Estey
Nov 22 '18 at 22:24
If your platform supports memory-mapped files, you don't have to choose.
– EOF
Nov 22 '18 at 23:28
I read the first paragraph and now I'm imagining 65,356 processes each taking its turn to write to the single shared output file. Even with far fewer processes in play this is going to look pretty much like a serial program and it's not a good outline design.
– High Performance Mark
Nov 23 '18 at 8:32