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/*************************************************************************
* Copyright (C) 2008 Tavian Barnes <tavianator@gmail.com> *
* *
* This file is part of The Sandglass Library. *
* *
* The Sandglass Library is free software; you can redistribute it *
* and/or modify it under the terms of the GNU Lesser General Public *
* License as published by the Free Software Foundation; either version *
* 3 of the License, or (at your option) any later version. *
* *
* The Sandglass Library is distributed in the hope that it will be *
* useful, but WITHOUT ANY WARRANTY; without even the implied warranty *
* of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU *
* Lesser General Public License for more details. *
* *
* You should have received a copy of the GNU Lesser General Public *
* License along with this program. If not, see *
* <http://www.gnu.org/licenses/>. *
*************************************************************************/
/*
* libsandglass - a library for extremely high-resolution timing, benchmarking,
* and profiling.
*/
#ifndef SANDGLASS_H_INCLUDED
#define SANDGLASS_H_INCLUDED
#ifdef __cplusplus
/* We've been included from a C++ file; mark everything here as extern "C" */
extern "C" {
#endif
/* A type to represent a clock's time measurement attributes */
enum sandglass_incrementation_t
{
/*
* A clock which only increments during the current process's execution. Less
* precise than a monotonic clock, but more accurate and useful for profiling
* longer operations.
*/
SANDGLASS_INTROSPECTIVE,
/*
* A clock which increments in real-time, regardless of whether the current
* process was executing during that time or not. Allows for greater timing
* resolution, but will be inaccurate if the process is context-switched
* while being timed.
*/
SANDGLASS_MONOTONIC
};
typedef enum sandglass_incrementation_t sandglass_incrementation_t;
/* A type to represent a clock's timing resolution */
enum sandglass_resolution_t
{
/*
* Rely on the kernel to provide time information; less precise, more
* portable. Uses times().
*/
SANDGLASS_SYSTEM,
/*
* Get timing information directly from the processor; more precise, less
* portable. Uses the CLOCK_THREAD_CPUTIME_ID clock for
* SANDGLASS_INTROSPECTIVE mode, and the raw TSC for SANDGLASS_MONOTONIC.
*/
SANDGLASS_CPUTIME,
/*
* Get timing information accurate to within one CPU clock cycle - requires
* some looping and other trickery to account for TSCs which are not accurate
* to within one clock cycle. Not valid with SANDGLASS_INTROSPECTIVE.
*/
SANDGLASS_REALTICKS
};
typedef enum sandglass_resolution_t sandglass_resolution_t;
/* Attributes of a clock */
struct sandglass_attributes_t
{
sandglass_incrementation_t incrementation;
sandglass_resolution_t resolution;
};
typedef struct sandglass_attributes_t sandglass_attributes_t;
struct sandglass_t
{
/* The attributes of the clock */
sandglass_attributes_t attributes;
/* Units of time which have passed */
long grains;
/* grains/resolution should give elapsed time in seconds */
double resolution;
/*
* Internal fields
*/
/* Adjustment to be added for negative (i.e. overflowed) grains counts */
long adjustment;
/* For SANDGLASS_TICKS looping support */
unsigned int i, loops;
};
typedef struct sandglass_t sandglass_t;
/*
* Creates a timer with at least the precision of `min', and at most the
* precision of `max'. Precisions are compared first by incrementation type:
* all monotonic timers are considered more precise than introspective timers.
* Then, higher resolution timers take precidence.
*
* If `min' is NULL, it defaults to { SANDGLASS_INTROSPECTIVE,
* SANDGLASS_SYSTEM }.
*
* If `max' is NULL, it defaults to at least `min', but not less than
* { SANDGLASS_INTROSPECTIVE, SANDGLASS_CPUTIME }.
*/
int sandglass_create(sandglass_t *sandglass,
const sandglass_attributes_t *min,
const sandglass_attributes_t *max);
int sandglass_begin(sandglass_t *sandglass);
int sandglass_elapse(sandglass_t *sandglass);
/* Use this to prevent a loop from being unrolled */
#define SANDGLASS_NO_UNROLL() __asm__ __volatile__ ("")
/*
* Macro to facilitate correct benchmarking of blocks of code. May be called
* like so:
* sandglass_bench(&sandglass, f(x))
* or like so:
* sandglass_bench(&sandglass, {
* f(x);
* g(x);
* });
*/
#define sandglass_bench(sandglass, routine) \
do { \
routine; \
sandglass_begin(sandglass); \
for ((sandglass)->i = 0; \
(sandglass)->i < (sandglass)->loops; \
++(sandglass)->i) { \
SANDGLASS_NO_UNROLL(); \
routine; \
} \
sandglass_elapse(sandglass); \
} while (0)
#ifdef __cplusplus
}
#endif
#endif /* SANDGLASS_H_INCLUDED */
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