Why the incorrect data are read from fscanf?
Question
I trying to read the data by fscanf from file, then I printed the data. However, some of data are not correct. There are four column. Only third column data have a problem. The other column is no problem.
Small number is read from file correctly, but large data are saturated to 26843519. It looks data type limitation. but the number 26843519 is not the limitation number of specific data type.
I trying to change many data type. I still could not solve this issue.
Could you please help it?
Compling and running system : I7-4790, ubuntu 14.04.1 x86_64, gcc(g++) 4.8.4
Source:
while(!feof(trace_file))
{
double time;
unsigned long location;
unsigned int req_size, temp;
char op_type[10];
//fscanf(trace_file, "%s\t%lf\t%d\n", op_type, &time, &location);
fscanf(trace_file, "%lf %s %lu %d %d \n", &time, op_type, &location, &req_size, &temp);
// for debug
printf("[Application] OP : %s Location : %lu Time : %lf Size : %d\n", op_type, location, time, req_size);
Input data file:
(The third column is a problem.)
128166477394345573 Read 383496192 32768 113736
128166483087163644 Read 2822144 65536 71730
128166620794097839 Read 3221266432 4096 121008
128166624207799335 Read 3354624 49152 147664
128166624207887065 Read 2961408 57344 59933
128166624210238731 Read 368979968 65536 52003
128166624211812801 Read 395730944 65536 40423
128166624211962708 Read 442093568 65536 46765
128166624211968354 Read 437964800 65536 41118
128166624212755738 Read 396734464 49152 34979
128166624212868365 Read 386232320 20480 78602
128166624212905977 Read 398438400 45056 40989
128166624213527427 Read 378523648 65536 44536
128166624213988219 Read 404738048 65536 52490
128166624213996455 Read 404475904 65536 44254
128166624232905615 Read 381739008 65536 41223
128166624242878893 Read 439144448 57344 67882
128166624242935246 Read 3608576 57344 11528
128166624243149609 Read 386646016 65536 109663
128166624243365012 Read 398176256 65536 50510
128166624274398038 Read 397676544 32768 111035
128166624295029088 Read 6320128 65536 104853
Outputted results (by printf):
(The third data will be outputted to "Location".)
[Application] OP : Read Location : 26843519 Time : 128166477394345568.000000 Size : 32768
[Application] OP : Read Location : 2822144 Time : 128166483087163648.000000 Size : 65536
[Application] OP : Read Location : 26843519 Time : 128166620794097840.000000 Size : 4096
[Application] OP : Read Location : 3354624 Time : 128166624207799328.000000 Size : 49152
[Application] OP : Read Location : 2961408 Time : 128166624207887072.000000 Size : 57344
[Application] OP : Read Location : 26843519 Time : 128166624210238736.000000 Size : 65536
[Application] OP : Read Location : 26843519 Time : 128166624211812800.000000 Size : 65536
[Application] OP : Read Location : 26843519 Time : 128166624211962704.000000 Size : 65536
[Application] OP : Read Location : 26843519 Time : 128166624211968352.000000 Size : 65536
[Application] OP : Read Location : 26843519 Time : 128166624212755744.000000 Size : 49152
[Application] OP : Read Location : 26843519 Time : 128166624212868368.000000 Size : 20480
[Application] OP : Read Location : 26843519 Time : 128166624212905984.000000 Size : 45056
[Application] OP : Read Location : 26843519 Time : 128166624213527424.000000 Size : 65536
[Application] OP : Read Location : 26843519 Time : 128166624213988224.000000 Size : 65536
[Application] OP : Read Location : 26843519 Time : 128166624213996448.000000 Size : 65536
[Application] OP : Read Location : 26843519 Time : 128166624232905616.000000 Size : 65536
[Application] OP : Read Location : 26843519 Time : 128166624242878896.000000 Size : 57344
[Application] OP : Read Location : 3608576 Time : 128166624242935248.000000 Size : 57344
[Application] OP : Read Location : 26843519 Time : 128166624243149616.000000 Size : 65536
[Application] OP : Read Location : 26843519 Time : 128166624243365008.000000 Size : 65536
[Application] OP : Read Location : 26843519 Time : 128166624274398032.000000 Size : 32768
[Application] OP : Read Location : 6320128 Time : 128166624295029088.000000 Size : 65536
[Application] OP : Read Location : 26843519 Time : 128166624295087648.000000 Size : 49152
2 answers
solution1
1 2016-07-23 00:44:42
Your (updated) code works for me. In any case, it's not a problem with integer size unless you're using a very odd architecture. The first value to go wrong is 383,496,192, which can be represented in 28 bits (2^29 = 536,870,912).
solution2
1 ACCPTED 2016-07-23 00:48:04
If there is a question about architecture impacting integer size, the you can use the exact size integer representations provided by stdint.h and the scan and print macros in inttypes.h . For example, your code could be rewritten as:
#include <stdio.h>
#include <stdint.h> /* for uintX_t */
#include <inttypes.h> /* for SCNtX & PRItX */
int main (int argc, char **argv) {
double time;
uint64_t location; /* exact size variables */
uint32_t req_size, temp;
char op_type[10];
FILE *fp = argc > 1 ? fopen (argv[1], "r") : stdin;
if (!fp) { /* validate file open for reading */
fprintf (stderr, "error: file open failed '%s'.\n", argv[1]);
return 1;
}
/* using SCN with fscanf and PRI with printf */
while (fscanf (fp, "%lf %s %" SCNu64 " %" SCNu32 " %" SCNu32 "",
&time, op_type, &location, &req_size, &temp) == 5)
printf ("[Application] OP : %s Location : %10" PRIu64 " "
" Time : %.0lf Size : %5" PRIu32 "\n", op_type,
location, time, req_size);
if (fp != stdin) fclose (fp); /* close file if not stdin */
return 0;
}
That will eliminate any storage size differences.
Example Use/Output
$ ./bin/readloc <dat/location.txt
[Application] OP : Read Location : 383496192 Time : 128166477394345568 Size : 32768
[Application] OP : Read Location : 2822144 Time : 128166483087163648 Size : 65536
[Application] OP : Read Location : 3221266432 Time : 128166620794097840 Size : 4096
[Application] OP : Read Location : 3354624 Time : 128166624207799328 Size : 49152
[Application] OP : Read Location : 2961408 Time : 128166624207887072 Size : 57344
[Application] OP : Read Location : 368979968 Time : 128166624210238736 Size : 65536
[Application] OP : Read Location : 395730944 Time : 128166624211812800 Size : 65536
[Application] OP : Read Location : 442093568 Time : 128166624211962704 Size : 65536
[Application] OP : Read Location : 437964800 Time : 128166624211968352 Size : 65536
[Application] OP : Read Location : 396734464 Time : 128166624212755744 Size : 49152
[Application] OP : Read Location : 386232320 Time : 128166624212868368 Size : 20480
[Application] OP : Read Location : 398438400 Time : 128166624212905984 Size : 45056
[Application] OP : Read Location : 378523648 Time : 128166624213527424 Size : 65536
[Application] OP : Read Location : 404738048 Time : 128166624213988224 Size : 65536
[Application] OP : Read Location : 404475904 Time : 128166624213996448 Size : 65536
[Application] OP : Read Location : 381739008 Time : 128166624232905616 Size : 65536
[Application] OP : Read Location : 439144448 Time : 128166624242878896 Size : 57344
[Application] OP : Read Location : 3608576 Time : 128166624242935248 Size : 57344
[Application] OP : Read Location : 386646016 Time : 128166624243149616 Size : 65536
[Application] OP : Read Location : 398176256 Time : 128166624243365008 Size : 65536
[Application] OP : Read Location : 397676544 Time : 128166624274398032 Size : 32768
[Application] OP : Read Location : 6320128 Time : 128166624295029088 Size : 65536
Look it over, give it a try, and let me know if you have any questions.
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