Programming :: Difference In Time Recorded By Clock_gettime() And TSC?
Jan 24, 2011
I want to measure the time it takes to execute a C function. The question is which is the best method to record time. After a lot of searching online, I found two ways [URL]:
a. using clock_gettime(CLOCK_MONOTONIC, &t)
b. using TSC
I call the C function 50 times (recording the time it takes for each call). The average is found only for the last 35 calls.
Using (a), I get:
48345 us
28350 us
28379 us
27716 us
[code]....
Average time for the last 35 loops: 121450.47 microseconds
Using (b), I get:
48130 cycles
28726 cycles
28820 cycles
27421 cycles
[code]....
Average for the last 35 loops: 27236.66 cycles What could be causing the strange value of 3322259 us in method (a)? I could just use method (b) but I would like to know what is going on here... Btw, I am using a desktop - with Linux debian 2.6.26 #1 SMP.
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Jan 28, 2010
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undefined reference to `clock_gettime'
..even though I have #include "time.h" Here is my uber-goal:
// Returns fractional seconds that have elapsed since Start_Ticks was set.
float elapsed_seconds( unsigned Start_Ticks )
{
[code]....
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Code:
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[Code]...
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[Code]....
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Quote:
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Code:
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[Code].....
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[URL]
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Code:
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Code:
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-- I tested it on the both OS in the same situation as possible as I can.
(reboot->test)
-- BTW 64bit one doesn't have those programs. I just installed on my external hard drive, so it's literary PURE one. (32bit one also in the same HDD)
-- I run these Ubuntus on VMware
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