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Overview
Comment:merge 8-5-timerate (?max-count?, break possibility, diverse fixes) + windows time-calibration cycle optimization [f6637d3dd8] (clock ticks never backwards, more precise and smooth drifting)
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Timelines: family | ancestors | sebres-8-6-timerate
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SHA3-256:2f5413a0fbac15d07e2a9766cf6c3a63109100bcdcad6287d4a91405ae5b4600
User & Date: sebres 2019-02-13 02:57:07
Context
2019-02-13
02:57
merge 8-5-timerate (?max-count?, break possibility, diverse fixes) + windows time-calibration cycle ... Leaf check-in: 2f5413a0fb user: sebres tags: sebres-8-6-timerate
01:22
timerate documentation extended Leaf check-in: af42c485d8 user: sebres tags: sebres-8-5-timerate
2019-02-07
21:20
timerate: added dynamic factor by threshold calculation (avoid growing of the execution time if iter... check-in: 8ad25ef9eb user: sebres tags: sebres-8-6-timerate
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to doc/timerate.n.

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.TH timerate n "" Tcl "Tcl Built-In Commands"
.so man.macros
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
timerate \- Time-related execution resp. performance measurement of a script
.SH SYNOPSIS
\fBtimerate \fIscript\fR \fI?time?\fR
.sp
\fBtimerate \fI?-direct?\fR \fI?-overhead double?\fR \fIscript\fR \fI?time?\fR
.sp
\fBtimerate \fI?-calibrate?\fR \fI?-direct?\fR \fIscript\fR \fI?time?\fR
.BE
.SH DESCRIPTION
.PP
The first and second form will evaluate \fIscript\fR until the interval
\fItime\fR given in milliseconds elapses, or for 1000 milliseconds (1 second)
if \fItime\fR is not specified. 



.sp
It will then return a canonical tcl-list of the form
.PP
.CS
\f0.095977 µs/# 52095836 # 10419167 #/sec 5000.000 nett-ms\fR
.CE
.PP







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.TH timerate n "" Tcl "Tcl Built-In Commands"
.so man.macros
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
timerate \- Time-related execution resp. performance measurement of a script
.SH SYNOPSIS
\fBtimerate \fIscript\fR \fI?time ?max-count??\fR
.sp
\fBtimerate \fI?-direct?\fR \fI?-overhead double?\fR \fIscript\fR \fI?time ?max-count??\fR
.sp
\fBtimerate \fI?-calibrate?\fR \fI?-direct?\fR \fIscript\fR \fI?time ?max-count??\fR
.BE
.SH DESCRIPTION
.PP
The first and second form will evaluate \fIscript\fR until the interval
\fItime\fR given in milliseconds elapses, or for 1000 milliseconds (1 second)
if \fItime\fR is not specified.
.sp
If \fImax-count\fR is specified, it imposes a further restriction by the maximal 
number of iterations.
.sp
It will then return a canonical tcl-list of the form
.PP
.CS
\f0.095977 µs/# 52095836 # 10419167 #/sec 5000.000 nett-ms\fR
.CE
.PP

Changes to generic/tclCmdMZ.c.

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    static 
    double measureOverhead = 0; /* global measure-overhead */
    double overhead = -1;	/* given measure-overhead */
    register Tcl_Obj *objPtr;
    register int result, i;
    Tcl_Obj *calibrate = NULL, *direct = NULL;
    Tcl_WideUInt count = 0;	/* Holds repetition count */
    Tcl_WideInt maxms = -0x7FFFFFFFFFFFFFFFL; 
				/* Maximal running time (in milliseconds) */


    Tcl_WideUInt threshold = 1;	/* Current threshold for check time (faster
				 * repeat count without time check) */
    Tcl_WideUInt maxIterTm = 1;	/* Max time of some iteration as max threshold
				 * additionally avoid divide to zero (never < 1) */
    unsigned short factor = 50;	/* Factor (4..50) limiting threshold to avoid
				 * growth of execution time. */
    register Tcl_WideInt start, middle, stop;
................................................................................
	    break;
	case TMRT_CALIBRATE:
	    calibrate = objv[i];
	    break;
	}
    }

    if (i >= objc || i < objc-2) {
usage:
	Tcl_WrongNumArgs(interp, 1, objv, "?-direct? ?-calibrate? ?-overhead double? command ?time?");
	return TCL_ERROR;
    }
    objPtr = objv[i++];
    if (i < objc) {






	result = TclGetWideIntFromObj(interp, objv[i], &maxms);
	if (result != TCL_OK) {
	    return result;


	}
    }

    /* if calibrate */
    if (calibrate) {

	/* if no time specified for the calibration */
	if (maxms == -0x7FFFFFFFFFFFFFFFL) {
	    Tcl_Obj *clobjv[6];
	    Tcl_WideInt maxCalTime = 5000;
	    double lastMeasureOverhead = measureOverhead;
	    
	    clobjv[0] = objv[0]; 
	    i = 1;
	    if (direct) {
................................................................................
	    }

	    i--;
	    clobjv[i++] = calibrate;
	    clobjv[i++] = objPtr; 

	    /* set last measurement overhead to max */
	    measureOverhead = (double)0x7FFFFFFFFFFFFFFFL;

	    /* calibration cycle until it'll be preciser */
	    maxms = -1000;
	    do {
		lastMeasureOverhead = measureOverhead;
		TclNewLongObj(clobjv[i], (int)maxms);
		Tcl_IncrRefCount(clobjv[i]);
................................................................................
	    Tcl_SetObjResult(interp, Tcl_NewLongObj(0));
	    return TCL_OK;
	}

	/* if time is negative - make current overhead more precise */
	if (maxms > 0) {
	    /* set last measurement overhead to max */
	    measureOverhead = (double)0x7FFFFFFFFFFFFFFFL;
	} else {
	    maxms = -maxms;
	}

    }

    if (maxms == -0x7FFFFFFFFFFFFFFFL) {
    	maxms = 1000;
    }
    if (overhead == -1) {
	overhead = measureOverhead;
    }

    /* be sure that resetting of result will not smudge the further measurement */
................................................................................
    start = now.sec; start *= 1000000; start += now.usec;
    middle = start;
    /* time to stop execution (in microsecs) */
    stop = start + maxms * 1000;
#endif

    /* start measurement */

    while (1) {
    	/* eval single iteration */
    	count++;

	if (!direct) {
	    /* precompiled */
	    rootPtr = TOP_CB(interp);
................................................................................
	    result = TclNRExecuteByteCode(interp, codePtr);
	    result = TclNRRunCallbacks(interp, result, rootPtr);
	} else {
	    /* eval */
	    result = TclEvalObjEx(interp, objPtr, 0, NULL, 0);
	}
	if (result != TCL_OK) {


	    goto done;





	}
	
	/* don't check time up to threshold */
	if (--threshold > 0) continue;

	/* check stop time reached, estimate new threshold */
    #ifdef TCL_WIDE_CLICKS
	middle = TclpGetWideClicks();
    #else
	Tcl_GetTime(&now);
	middle = now.sec; middle *= 1000000; middle += now.usec;
    #endif
	if (middle >= stop) {
	    break;
	}

	/* don't calculate threshold by few iterations, because sometimes first
	 * iteration(s) can be too fast or slow (cached, delayed clean up, etc) */
	if (count < 10) {
	   threshold = 1; continue;
................................................................................
	/* as relation between remaining time and time since last check,
	 * maximal some % of time (by factor), so avoid growing of the execution time
	 * if iterations are not consistent, e. g. wax continuously on time) */
	threshold = ((stop - middle) / maxIterTm) / factor + 1;
	if (threshold > 100000) {	    /* fix for too large threshold */
	    threshold = 100000;
	}




    }

    {
	Tcl_Obj *objarr[8], **objs = objarr;
	Tcl_WideInt val;
	const char *fmt;

................................................................................
    #endif

	/* if not calibrate */
	if (!calibrate) {
	    /* minimize influence of measurement overhead */
	    if (overhead > 0) {
		/* estimate the time of overhead (microsecs) */
		Tcl_WideInt curOverhead = overhead * count;
		if (middle > curOverhead) {
		    middle -= curOverhead;
		} else {
		    middle = 1;
		}
	    }
	} else {
	    /* calibration - obtaining new measurement overhead */
	    if (measureOverhead > (double)middle / count) {
		measureOverhead = (double)middle / count;
	    }
................................................................................
	    objs[0] = Tcl_ObjPrintf(fmt, ((double)middle)/count);
	}

	objs[2] = Tcl_NewWideIntObj(count); /* iterations */
	
	/* calculate speed as rate (count) per sec */
	if (!middle) middle++; /* +1 ms, just to avoid divide by zero */
	if (count < (0x7FFFFFFFFFFFFFFFL / 1000000)) {
	    val = (count * 1000000) / middle;
	    if (val < 100000) {
		if (val < 100)	{ fmt = "%.3f"; } else
		if (val < 1000) { fmt = "%.2f"; } else
				{ fmt = "%.1f"; };
		objs[4] = Tcl_ObjPrintf(fmt, ((double)(count * 1000000)) / middle);
	    } else {







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    static 
    double measureOverhead = 0; /* global measure-overhead */
    double overhead = -1;	/* given measure-overhead */
    register Tcl_Obj *objPtr;
    register int result, i;
    Tcl_Obj *calibrate = NULL, *direct = NULL;
    Tcl_WideUInt count = 0;	/* Holds repetition count */
    Tcl_WideInt  maxms  = WIDE_MIN;
				/* Maximal running time (in milliseconds) */
    Tcl_WideUInt maxcnt = WIDE_MAX;
				/* Maximal count of iterations. */
    Tcl_WideUInt threshold = 1;	/* Current threshold for check time (faster
				 * repeat count without time check) */
    Tcl_WideUInt maxIterTm = 1;	/* Max time of some iteration as max threshold
				 * additionally avoid divide to zero (never < 1) */
    unsigned short factor = 50;	/* Factor (4..50) limiting threshold to avoid
				 * growth of execution time. */
    register Tcl_WideInt start, middle, stop;
................................................................................
	    break;
	case TMRT_CALIBRATE:
	    calibrate = objv[i];
	    break;
	}
    }

    if (i >= objc || i < objc-3) {
usage:
	Tcl_WrongNumArgs(interp, 1, objv, "?-direct? ?-calibrate? ?-overhead double? command ?time ?max-count??");
	return TCL_ERROR;
    }
    objPtr = objv[i++];
    if (i < objc) {	/* max-time */
	result = Tcl_GetWideIntFromObj(interp, objv[i++], &maxms);
	if (result != TCL_OK) {
	    return result;
	}
	if (i < objc) {	/* max-count*/
	    Tcl_WideInt v;
	    result = Tcl_GetWideIntFromObj(interp, objv[i], &v);
	    if (result != TCL_OK) {
		return result;
	    }
	    maxcnt = (v > 0) ? v : 0;
	}
    }

    /* if calibrate */
    if (calibrate) {

	/* if no time specified for the calibration */
	if (maxms == WIDE_MIN) {
	    Tcl_Obj *clobjv[6];
	    Tcl_WideInt maxCalTime = 5000;
	    double lastMeasureOverhead = measureOverhead;
	    
	    clobjv[0] = objv[0]; 
	    i = 1;
	    if (direct) {
................................................................................
	    }

	    i--;
	    clobjv[i++] = calibrate;
	    clobjv[i++] = objPtr; 

	    /* set last measurement overhead to max */
	    measureOverhead = (double)UWIDE_MAX;

	    /* calibration cycle until it'll be preciser */
	    maxms = -1000;
	    do {
		lastMeasureOverhead = measureOverhead;
		TclNewLongObj(clobjv[i], (int)maxms);
		Tcl_IncrRefCount(clobjv[i]);
................................................................................
	    Tcl_SetObjResult(interp, Tcl_NewLongObj(0));
	    return TCL_OK;
	}

	/* if time is negative - make current overhead more precise */
	if (maxms > 0) {
	    /* set last measurement overhead to max */
	    measureOverhead = (double)UWIDE_MAX;
	} else {
	    maxms = -maxms;
	}

    }

    if (maxms == WIDE_MIN) {
    	maxms = 1000;
    }
    if (overhead == -1) {
	overhead = measureOverhead;
    }

    /* be sure that resetting of result will not smudge the further measurement */
................................................................................
    start = now.sec; start *= 1000000; start += now.usec;
    middle = start;
    /* time to stop execution (in microsecs) */
    stop = start + maxms * 1000;
#endif

    /* start measurement */
    if (maxcnt > 0)
    while (1) {
    	/* eval single iteration */
    	count++;

	if (!direct) {
	    /* precompiled */
	    rootPtr = TOP_CB(interp);
................................................................................
	    result = TclNRExecuteByteCode(interp, codePtr);
	    result = TclNRRunCallbacks(interp, result, rootPtr);
	} else {
	    /* eval */
	    result = TclEvalObjEx(interp, objPtr, 0, NULL, 0);
	}
	if (result != TCL_OK) {
	    /* allow break from measurement cycle (used for conditional stop) */
	    if (result != TCL_BREAK) {
		goto done;
	    }
	    /* force stop immediately */
	    threshold = 1;
	    maxcnt = 0;
	    result = TCL_OK;
	}
	
	/* don't check time up to threshold */
	if (--threshold > 0) continue;

	/* check stop time reached, estimate new threshold */
    #ifdef TCL_WIDE_CLICKS
	middle = TclpGetWideClicks();
    #else
	Tcl_GetTime(&now);
	middle = now.sec; middle *= 1000000; middle += now.usec;
    #endif
	if (middle >= stop || count >= maxcnt) {
	    break;
	}

	/* don't calculate threshold by few iterations, because sometimes first
	 * iteration(s) can be too fast or slow (cached, delayed clean up, etc) */
	if (count < 10) {
	   threshold = 1; continue;
................................................................................
	/* as relation between remaining time and time since last check,
	 * maximal some % of time (by factor), so avoid growing of the execution time
	 * if iterations are not consistent, e. g. wax continuously on time) */
	threshold = ((stop - middle) / maxIterTm) / factor + 1;
	if (threshold > 100000) {	    /* fix for too large threshold */
	    threshold = 100000;
	}
	/* consider max-count */
	if (threshold > maxcnt - count) {
	    threshold = maxcnt - count;
	}
    }

    {
	Tcl_Obj *objarr[8], **objs = objarr;
	Tcl_WideInt val;
	const char *fmt;

................................................................................
    #endif

	/* if not calibrate */
	if (!calibrate) {
	    /* minimize influence of measurement overhead */
	    if (overhead > 0) {
		/* estimate the time of overhead (microsecs) */
		Tcl_WideUInt curOverhead = overhead * count;
		if (middle > curOverhead) {
		    middle -= curOverhead;
		} else {
		    middle = 0;
		}
	    }
	} else {
	    /* calibration - obtaining new measurement overhead */
	    if (measureOverhead > (double)middle / count) {
		measureOverhead = (double)middle / count;
	    }
................................................................................
	    objs[0] = Tcl_ObjPrintf(fmt, ((double)middle)/count);
	}

	objs[2] = Tcl_NewWideIntObj(count); /* iterations */
	
	/* calculate speed as rate (count) per sec */
	if (!middle) middle++; /* +1 ms, just to avoid divide by zero */
	if (count < (WIDE_MAX / 1000000)) {
	    val = (count * 1000000) / middle;
	    if (val < 100000) {
		if (val < 100)	{ fmt = "%.3f"; } else
		if (val < 1000) { fmt = "%.2f"; } else
				{ fmt = "%.1f"; };
		objs[4] = Tcl_ObjPrintf(fmt, ((double)(count * 1000000)) / middle);
	    } else {

Changes to generic/tclPort.h.

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#         define LLONG_MIN ((Tcl_WideInt)(Tcl_LongAsWide(1)<<63))
#      endif
#   endif
/* Assume that if LLONG_MIN is undefined, then so is LLONG_MAX */
#   define LLONG_MAX (~LLONG_MIN)
#endif





#endif /* _TCLPORT */







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#         define LLONG_MIN ((Tcl_WideInt)(Tcl_LongAsWide(1)<<63))
#      endif
#   endif
/* Assume that if LLONG_MIN is undefined, then so is LLONG_MAX */
#   define LLONG_MAX (~LLONG_MIN)
#endif

#define UWIDE_MAX ((Tcl_WideUInt)-1)
#define WIDE_MAX ((Tcl_WideInt)(UWIDE_MAX >> 1))
#define WIDE_MIN ((Tcl_WideInt)((Tcl_WideUInt)WIDE_MAX+1))

#endif /* _TCLPORT */

Changes to tests/cmdMZ.test.

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test cmdMZ-5.7 {Tcl_TimeObjCmd: errors generate right trace} {
    list [catch {time {error foo}} msg] $msg $::errorInfo
} {1 foo {foo
    while executing
"error foo"
    invoked from within
"time {error foo}"}}

































































# The tests for Tcl_WhileObjCmd are in while.test
 
# cleanup
cleanupTests
}
namespace delete ::tcl::test::cmdMZ
return

# Local Variables:
# mode: tcl
# End:







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test cmdMZ-5.7 {Tcl_TimeObjCmd: errors generate right trace} {
    list [catch {time {error foo}} msg] $msg $::errorInfo
} {1 foo {foo
    while executing
"error foo"
    invoked from within
"time {error foo}"}}

test cmdMZ-6.1 {Tcl_TimeRateObjCmd: basic format of command} {
    list [catch {timerate} msg] $msg
} {1 {wrong # args: should be "timerate ?-direct? ?-calibrate? ?-overhead double? command ?time ?max-count??"}}
test cmdMZ-6.2.1 {Tcl_TimeRateObjCmd: basic format of command} {
    list [catch {timerate a b c d} msg] $msg
} {1 {wrong # args: should be "timerate ?-direct? ?-calibrate? ?-overhead double? command ?time ?max-count??"}}
test cmdMZ-6.2.2 {Tcl_TimeRateObjCmd: basic format of command} {
    list [catch {timerate a b c} msg] $msg
} {1 {expected integer but got "b"}}
test cmdMZ-6.2.3 {Tcl_TimeRateObjCmd: basic format of command} {
    list [catch {timerate a b} msg] $msg
} {1 {expected integer but got "b"}}
test cmdMZ-6.3 {Tcl_TimeRateObjCmd: basic format of command} {
    list [catch {timerate -overhead b {} a b} msg] $msg
} {1 {expected floating-point number but got "b"}}
test cmdMZ-6.4 {Tcl_TimeRateObjCmd: compile of script happens even with negative iteration counts} {
    list [catch {timerate "foreach a {c d e} \{" -12456} msg] $msg
} {1 {missing close-brace}}
test cmdMZ-6.5 {Tcl_TimeRateObjCmd: result format and one iteration} {
    regexp {^\d+.\d+ \ws/# 1 # \d+ #/sec \d+.\d+ nett-ms$} [timerate {} 0]
} 1
test cmdMZ-6.6 {Tcl_TimeRateObjCmd: slower commands take longer, but it remains almost the same time of measument} {
    set m1 [timerate {after 0} 20]
    set m2 [timerate {after 1} 20]
    list \
	[expr {[lindex $m1 0] < [lindex $m2 0]}] \
	[expr {[lindex $m1 0] < 100}] \
	[expr {[lindex $m2 0] >= 500}] \
	[expr {[lindex $m1 2] > 1000}] \
	[expr {[lindex $m2 2] <= 50}] \
	[expr {[lindex $m1 4] > 10000}] \
	[expr {[lindex $m2 4] < 10000}] \
	[expr {[lindex $m1 6] > 10 && [lindex $m1 6] < 50}] \
	[expr {[lindex $m2 6] > 10 && [lindex $m2 6] < 50}]
} [lrepeat 9 1]
test cmdMZ-6.7 {Tcl_TimeRateObjCmd: errors generate right trace} {
    list [catch {timerate {error foo} 1} msg] $msg $::errorInfo
} {1 foo {foo
    while executing
"error foo"
    invoked from within
"timerate {error foo} 1"}}
test cmdMZ-6.8 {Tcl_TimeRateObjCmd: allow (conditional) break from timerate} {
    set m1 [timerate {break}]
    list \
	[expr {[lindex $m1 0] < 1000}] \
	[expr {[lindex $m1 2] == 1}] \
	[expr {[lindex $m1 4] > 1000}] \
	[expr {[lindex $m1 6] < 10}]
} {1 1 1 1}
test cmdMZ-6.9 {Tcl_TimeRateObjCmd: max count of iterations} {
    set m1 [timerate {} 1000 5];	# max-count wins
    set m2 [timerate {after 20} 1 5];	# max-time wins
    list [lindex $m1 2] [lindex $m2 2]
} {5 1}
test cmdMZ-6.10 {Tcl_TimeRateObjCmd: huge overhead cause 0us result} {
    set m1 [timerate -overhead 1e6 {after 10} 100 1]
    list \
	[expr {[lindex $m1 0] == 0.0}] \
	[expr {[lindex $m1 2] == 1}] \
	[expr {[lindex $m1 4] == 1000000}] \
	[expr {[lindex $m1 6] <= 0.001}]
} {1 1 1 1}

# The tests for Tcl_WhileObjCmd are in while.test
 
# cleanup
cleanupTests
}
namespace delete ::tcl::test::cmdMZ
return

# Local Variables:
# mode: tcl
# End:

Changes to win/tclWinTime.c.

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typedef struct TimeInfo {
    CRITICAL_SECTION cs;	/* Mutex guarding this structure. */
    int initialized;		/* Flag == 1 if this structure is
				 * initialized. */
    int perfCounterAvailable;	/* Flag == 1 if the hardware has a performance
				 * counter. */

    HANDLE calibrationThread;	/* Handle to the thread that keeps the virtual
				 * clock calibrated. */
    HANDLE readyEvent;		/* System event used to trigger the requesting
				 * thread when the clock calibration procedure
				 * is initialized for the first time. */
    HANDLE exitEvent; 		/* Event to signal out of an exit handler to
				 * tell the calibration loop to terminate. */
    LARGE_INTEGER nominalFreq;	/* Nominal frequency of the system performance
				 * counter, that is, the value returned from
				 * QueryPerformanceFrequency. */

    /*
     * The following values are used for calculating virtual time. Virtual
     * time is always equal to:
     *    lastFileTime + (current perf counter - lastCounter)
     *				* 10000000 / curCounterFreq
     * and lastFileTime and lastCounter are updated any time that virtual time
     * is returned to a caller.
     */

    ULARGE_INTEGER fileTimeLastCall;
    LARGE_INTEGER perfCounterLastCall;
    LARGE_INTEGER curCounterFreq;



    /*
     * Data used in developing the estimate of performance counter frequency
     */

    Tcl_WideUInt fileTimeSample[SAMPLES];
				/* Last 64 samples of system time. */
................................................................................
    int sampleNo;		/* Current sample number. */
} TimeInfo;

static TimeInfo timeInfo = {
    { NULL, 0, 0, NULL, NULL, 0 },
    0,
    0,

    (HANDLE) NULL,
    (HANDLE) NULL,
    (HANDLE) NULL,
#ifdef HAVE_CAST_TO_UNION
    (LARGE_INTEGER) (Tcl_WideInt) 0,
    (ULARGE_INTEGER) (DWORDLONG) 0,
    (LARGE_INTEGER) (Tcl_WideInt) 0,
    (LARGE_INTEGER) (Tcl_WideInt) 0,

#else
    0,
    0,
    0,
    0,

#endif
    { 0 },
    { 0 },
    0
};

/*
................................................................................
 *	clock (obtained through ftime) and the frequency of the performance
 *	counter. Also spins a thread whose function is to wake up periodically
 *	and monitor these values, adjusting them as necessary to correct for
 *	drift in the performance counter's oscillator.
 *
 *----------------------------------------------------------------------
 */












static Tcl_WideInt
NativeGetMicroseconds(void)
{
    static LARGE_INTEGER posixEpoch;
				/* Posix epoch expressed as 100-ns ticks since
				 * the windows epoch. */
    /*
     * Initialize static storage on the first trip through.
     *
     * Note: Outer check for 'initialized' is a performance win since it
     * avoids an extra mutex lock in the common case.
     */

    if (!timeInfo.initialized) {
	TclpInitLock();
	if (!timeInfo.initialized) {

	    posixEpoch.LowPart = 0xD53E8000;
	    posixEpoch.HighPart = 0x019DB1DE;

	    timeInfo.perfCounterAvailable =
		    QueryPerformanceFrequency(&timeInfo.nominalFreq);

	    /*
	     * Some hardware abstraction layers use the CPU clock in place of
	     * the real-time clock as a performance counter reference. This
................................................................................

    if (timeInfo.perfCounterAvailable && timeInfo.curCounterFreq.QuadPart!=0) {
	/*
	 * Query the performance counter and use it to calculate the current
	 * time.
	 */

	ULARGE_INTEGER fileTimeLastCall;
	LARGE_INTEGER perfCounterLastCall, curCounterFreq;
				/* Copy with current data of calibration cycle */

	LARGE_INTEGER curCounter;
				/* Current performance counter. */
	Tcl_WideInt curFileTime;/* Current estimated time, expressed as 100-ns
				 * ticks since the Windows epoch. */
	Tcl_WideInt usecSincePosixEpoch;
				/* Current microseconds since Posix epoch. */

	QueryPerformanceCounter(&curCounter);

	/*
	 * Hold time section locked as short as possible
	 */
	EnterCriticalSection(&timeInfo.cs);

	fileTimeLastCall.QuadPart = timeInfo.fileTimeLastCall.QuadPart;
	perfCounterLastCall.QuadPart = timeInfo.perfCounterLastCall.QuadPart;
	curCounterFreq.QuadPart = timeInfo.curCounterFreq.QuadPart;

	LeaveCriticalSection(&timeInfo.cs);

	/*
	 * If calibration cycle occurred after we get curCounter
	 */
	if (curCounter.QuadPart <= perfCounterLastCall.QuadPart) {
	    usecSincePosixEpoch =
		(fileTimeLastCall.QuadPart - posixEpoch.QuadPart) / 10;
	    return usecSincePosixEpoch;
	}

	/*
	 * If it appears to be more than 1.1 seconds since the last trip
	 * through the calibration loop, the performance counter may have
	 * jumped forward. (See MSDN Knowledge Base article Q274323 for a
	 * description of the hardware problem that makes this test
	 * necessary.) If the counter jumps, we don't want to use it directly.
	 * Instead, we must return system time. Eventually, the calibration
	 * loop should recover.
	 */

	if (curCounter.QuadPart - perfCounterLastCall.QuadPart <
		11 * curCounterFreq.QuadPart / 10
	) {

	    curFileTime = fileTimeLastCall.QuadPart +
		 ((curCounter.QuadPart - perfCounterLastCall.QuadPart)
		    * 10000000 / curCounterFreq.QuadPart);

	    usecSincePosixEpoch = (curFileTime - posixEpoch.QuadPart) / 10;
	    return usecSincePosixEpoch;
	}
    }

    /*
     * High resolution timer is not available.
     */
    return 0;
................................................................................
 *
 * Side effects:
 *	Sets the 'exitEvent' event in the 'timeInfo' structure to ask the
 *	thread in question to exit, and waits for it to do so.
 *
 *----------------------------------------------------------------------
 */



static void
StopCalibration(
    ClientData unused)		/* Client data is unused */
{
    SetEvent(timeInfo.exitEvent);

................................................................................
     */

    GetSystemTimeAsFileTime(&curFileTime);
    QueryPerformanceCounter(&timeInfo.perfCounterLastCall);
    QueryPerformanceFrequency(&timeInfo.curCounterFreq);
    timeInfo.fileTimeLastCall.LowPart = curFileTime.dwLowDateTime;
    timeInfo.fileTimeLastCall.HighPart = curFileTime.dwHighDateTime;



    ResetCounterSamples(timeInfo.fileTimeLastCall.QuadPart,
	    timeInfo.perfCounterLastCall.QuadPart,
	    timeInfo.curCounterFreq.QuadPart);

    /*
     * Wake up the calling thread. When it wakes up, it will release the
................................................................................
static void
UpdateTimeEachSecond(void)
{
    LARGE_INTEGER curPerfCounter;
				/* Current value returned from
				 * QueryPerformanceCounter. */
    FILETIME curSysTime;	/* Current system time. */

    LARGE_INTEGER curFileTime;	/* File time at the time this callback was
				 * scheduled. */
    Tcl_WideInt estFreq;	/* Estimated perf counter frequency. */
    Tcl_WideInt vt0;		/* Tcl time right now. */
    Tcl_WideInt vt1;		/* Tcl time one second from now. */
    Tcl_WideInt tdiff;		/* Difference between system clock and Tcl
				 * time. */
    Tcl_WideInt driftFreq;	/* Frequency needed to drift virtual time into
				 * step over 1 second. */

    /*
     * Sample performance counter and system time.
     */

    QueryPerformanceCounter(&curPerfCounter);
    GetSystemTimeAsFileTime(&curSysTime);
    curFileTime.LowPart = curSysTime.dwLowDateTime;
    curFileTime.HighPart = curSysTime.dwHighDateTime;









    EnterCriticalSection(&timeInfo.cs);




    /*
     * We devide by timeInfo.curCounterFreq.QuadPart in several places. That
     * value should always be positive on a correctly functioning system. But
     * it is good to be defensive about such matters. So if something goes
     * wrong and the value does goes to zero, we clear the
     * timeInfo.perfCounterAvailable in order to cause the calibration thread
     * to shut itself down, then return without additional processing.
     */

    if (timeInfo.curCounterFreq.QuadPart == 0){
	LeaveCriticalSection(&timeInfo.cs);
	timeInfo.perfCounterAvailable = 0;
	return;
    }

    /*
     * Several things may have gone wrong here that have to be checked for.
     *  (1) The performance counter may have jumped.
................................................................................
     *
     * vt1 = 20000000 + curFileTime
     *
     * The frequency that we need to use to drift the counter back into place
     * is estFreq * 20000000 / (vt1 - vt0)
     */

    vt0 = 10000000 * (curPerfCounter.QuadPart
		- timeInfo.perfCounterLastCall.QuadPart)
	    / timeInfo.curCounterFreq.QuadPart
	    + timeInfo.fileTimeLastCall.QuadPart;
    vt1 = 20000000 + curFileTime.QuadPart;

    /*
     * If we've gotten more than a second away from system time, then drifting
     * the clock is going to be pretty hopeless. Just let it jump. Otherwise,
     * compute the drift frequency and fill in everything.
     */

    tdiff = vt0 - curFileTime.QuadPart;
    if (tdiff > 10000000 || tdiff < -10000000) {

	timeInfo.fileTimeLastCall.QuadPart = curFileTime.QuadPart;
	timeInfo.curCounterFreq.QuadPart = estFreq;
    } else {


	driftFreq = estFreq * 20000000 / (vt1 - vt0);








	if (driftFreq > 1003*estFreq/1000) {
	    driftFreq = 1003*estFreq/1000;
	} else if (driftFreq < 997*estFreq/1000) {
	    driftFreq = 997*estFreq/1000;





	}


















	timeInfo.fileTimeLastCall.QuadPart = vt0;
	timeInfo.curCounterFreq.QuadPart = driftFreq;












    }
















    timeInfo.perfCounterLastCall.QuadPart = curPerfCounter.QuadPart;

    LeaveCriticalSection(&timeInfo.cs);
}
 
/*
 *----------------------------------------------------------------------







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typedef struct TimeInfo {
    CRITICAL_SECTION cs;	/* Mutex guarding this structure. */
    int initialized;		/* Flag == 1 if this structure is
				 * initialized. */
    int perfCounterAvailable;	/* Flag == 1 if the hardware has a performance
				 * counter. */
    DWORD calibrationInterv;	/* Calibration interval in seconds (start 1 sec) */
    HANDLE calibrationThread;	/* Handle to the thread that keeps the virtual
				 * clock calibrated. */
    HANDLE readyEvent;		/* System event used to trigger the requesting
				 * thread when the clock calibration procedure
				 * is initialized for the first time. */
    HANDLE exitEvent; 		/* Event to signal out of an exit handler to
				 * tell the calibration loop to terminate. */
    LARGE_INTEGER nominalFreq;	/* Nominal frequency of the system performance
				 * counter, that is, the value returned from
				 * QueryPerformanceFrequency. */

    /*
     * The following values are used for calculating virtual time. Virtual
     * time is always equal to:
     *    lastFileTime + (current perf counter - lastCounter)
     *				* 10000000 / curCounterFreq
     * and lastFileTime and lastCounter are updated any time that virtual time
     * is returned to a caller.
     */

    ULARGE_INTEGER fileTimeLastCall;
    LARGE_INTEGER perfCounterLastCall;
    LARGE_INTEGER curCounterFreq;
    LARGE_INTEGER posixEpoch;	/* Posix epoch expressed as 100-ns ticks since
				 * the windows epoch. */

    /*
     * Data used in developing the estimate of performance counter frequency
     */

    Tcl_WideUInt fileTimeSample[SAMPLES];
				/* Last 64 samples of system time. */
................................................................................
    int sampleNo;		/* Current sample number. */
} TimeInfo;

static TimeInfo timeInfo = {
    { NULL, 0, 0, NULL, NULL, 0 },
    0,
    0,
    1,
    (HANDLE) NULL,
    (HANDLE) NULL,
    (HANDLE) NULL,
#ifdef HAVE_CAST_TO_UNION
    (LARGE_INTEGER) (Tcl_WideInt) 0,
    (ULARGE_INTEGER) (DWORDLONG) 0,
    (LARGE_INTEGER) (Tcl_WideInt) 0,
    (LARGE_INTEGER) (Tcl_WideInt) 0,
    (LARGE_INTEGER) (Tcl_WideInt) 0,
#else
    {0, 0},
    {0, 0},
    {0, 0},
    {0, 0},
    {0, 0},
#endif
    { 0 },
    { 0 },
    0
};

/*
................................................................................
 *	clock (obtained through ftime) and the frequency of the performance
 *	counter. Also spins a thread whose function is to wake up periodically
 *	and monitor these values, adjusting them as necessary to correct for
 *	drift in the performance counter's oscillator.
 *
 *----------------------------------------------------------------------
 */

static inline Tcl_WideInt
NativeCalc100NsTicks(
    ULONGLONG fileTimeLastCall,
    LONGLONG perfCounterLastCall,
    LONGLONG curCounterFreq,
    LONGLONG curCounter
) {
    return fileTimeLastCall + 
	((curCounter - perfCounterLastCall) * 10000000 / curCounterFreq);
}

static Tcl_WideInt
NativeGetMicroseconds(void)
{



    /*
     * Initialize static storage on the first trip through.
     *
     * Note: Outer check for 'initialized' is a performance win since it
     * avoids an extra mutex lock in the common case.
     */

    if (!timeInfo.initialized) {
	TclpInitLock();
	if (!timeInfo.initialized) {

	    timeInfo.posixEpoch.LowPart = 0xD53E8000;
	    timeInfo.posixEpoch.HighPart = 0x019DB1DE;

	    timeInfo.perfCounterAvailable =
		    QueryPerformanceFrequency(&timeInfo.nominalFreq);

	    /*
	     * Some hardware abstraction layers use the CPU clock in place of
	     * the real-time clock as a performance counter reference. This
................................................................................

    if (timeInfo.perfCounterAvailable && timeInfo.curCounterFreq.QuadPart!=0) {
	/*
	 * Query the performance counter and use it to calculate the current
	 * time.
	 */

	ULONGLONG fileTimeLastCall;
	LONGLONG perfCounterLastCall, curCounterFreq;
				/* Copy with current data of calibration cycle */

	LARGE_INTEGER curCounter;
				/* Current performance counter. */





	QueryPerformanceCounter(&curCounter);

	/*
	 * Hold time section locked as short as possible
	 */
	EnterCriticalSection(&timeInfo.cs);

	fileTimeLastCall = timeInfo.fileTimeLastCall.QuadPart;
	perfCounterLastCall = timeInfo.perfCounterLastCall.QuadPart;
	curCounterFreq = timeInfo.curCounterFreq.QuadPart;

	LeaveCriticalSection(&timeInfo.cs);

	/*
	 * If calibration cycle occurred after we get curCounter
	 */
	if (curCounter.QuadPart <= perfCounterLastCall) {
	    /* Calibrated file-time is saved from posix in 100-ns ticks */
	    return fileTimeLastCall / 10;

	}

	/*
	 * If it appears to be more than 1.1 seconds since the last trip
	 * through the calibration loop, the performance counter may have
	 * jumped forward. (See MSDN Knowledge Base article Q274323 for a
	 * description of the hardware problem that makes this test
	 * necessary.) If the counter jumps, we don't want to use it directly.
	 * Instead, we must return system time. Eventually, the calibration
	 * loop should recover.
	 */

	if (curCounter.QuadPart - perfCounterLastCall <
		11 * curCounterFreq * timeInfo.calibrationInterv / 10
	) {
	    /* Calibrated file-time is saved from posix in 100-ns ticks */
	    return NativeCalc100NsTicks(fileTimeLastCall,

		perfCounterLastCall, curCounterFreq, curCounter.QuadPart) / 10;



	}
    }

    /*
     * High resolution timer is not available.
     */
    return 0;
................................................................................
 *
 * Side effects:
 *	Sets the 'exitEvent' event in the 'timeInfo' structure to ask the
 *	thread in question to exit, and waits for it to do so.
 *
 *----------------------------------------------------------------------
 */

void TclWinResetTimerResolution(void);

static void
StopCalibration(
    ClientData unused)		/* Client data is unused */
{
    SetEvent(timeInfo.exitEvent);

................................................................................
     */

    GetSystemTimeAsFileTime(&curFileTime);
    QueryPerformanceCounter(&timeInfo.perfCounterLastCall);
    QueryPerformanceFrequency(&timeInfo.curCounterFreq);
    timeInfo.fileTimeLastCall.LowPart = curFileTime.dwLowDateTime;
    timeInfo.fileTimeLastCall.HighPart = curFileTime.dwHighDateTime;
    /* Calibrated file-time will be saved from posix in 100-ns ticks */
    timeInfo.fileTimeLastCall.QuadPart -= timeInfo.posixEpoch.QuadPart;

    ResetCounterSamples(timeInfo.fileTimeLastCall.QuadPart,
	    timeInfo.perfCounterLastCall.QuadPart,
	    timeInfo.curCounterFreq.QuadPart);

    /*
     * Wake up the calling thread. When it wakes up, it will release the
................................................................................
static void
UpdateTimeEachSecond(void)
{
    LARGE_INTEGER curPerfCounter;
				/* Current value returned from
				 * QueryPerformanceCounter. */
    FILETIME curSysTime;	/* Current system time. */
    static LARGE_INTEGER lastFileTime; /* File time of the previous calibration */
    LARGE_INTEGER curFileTime;	/* File time at the time this callback was
				 * scheduled. */
    Tcl_WideInt estFreq;	/* Estimated perf counter frequency. */
    Tcl_WideInt vt0;		/* Tcl time right now. */
    Tcl_WideInt vt1;		/* Tcl time one second from now. */
    Tcl_WideInt tdiff;		/* Difference between system clock and Tcl
				 * time. */
    Tcl_WideInt driftFreq;	/* Frequency needed to drift virtual time into
				 * step over 1 second. */

    /*
     * Sample performance counter and system time (from posix epoch).
     */


    GetSystemTimeAsFileTime(&curSysTime);
    curFileTime.LowPart = curSysTime.dwLowDateTime;
    curFileTime.HighPart = curSysTime.dwHighDateTime;
    curFileTime.QuadPart -= timeInfo.posixEpoch.QuadPart;
    /* If calibration still not needed (check for possible time switch) */
    if ( curFileTime.QuadPart > lastFileTime.QuadPart
      && curFileTime.QuadPart < lastFileTime.QuadPart +
      				    (timeInfo.calibrationInterv * 10000000)
    ) {
    	/* again in next one second */
	return;
    }

    QueryPerformanceCounter(&curPerfCounter);
    
    lastFileTime.QuadPart = curFileTime.QuadPart;

    /*
     * We devide by timeInfo.curCounterFreq.QuadPart in several places. That
     * value should always be positive on a correctly functioning system. But
     * it is good to be defensive about such matters. So if something goes
     * wrong and the value does goes to zero, we clear the
     * timeInfo.perfCounterAvailable in order to cause the calibration thread
     * to shut itself down, then return without additional processing.
     */

    if (timeInfo.curCounterFreq.QuadPart == 0){

	timeInfo.perfCounterAvailable = 0;
	return;
    }

    /*
     * Several things may have gone wrong here that have to be checked for.
     *  (1) The performance counter may have jumped.
................................................................................
     *
     * vt1 = 20000000 + curFileTime
     *
     * The frequency that we need to use to drift the counter back into place
     * is estFreq * 20000000 / (vt1 - vt0)
     */

    vt0 = NativeCalc100NsTicks(timeInfo.fileTimeLastCall.QuadPart,
	    timeInfo.perfCounterLastCall.QuadPart, timeInfo.curCounterFreq.QuadPart,
	    curPerfCounter.QuadPart);



    /*
     * If we've gotten more than a second away from system time, then drifting
     * the clock is going to be pretty hopeless. Just let it jump. Otherwise,
     * compute the drift frequency and fill in everything.
     */

    tdiff = vt0 - curFileTime.QuadPart;
    if (tdiff > 10000000 || tdiff < -10000000) {
    	/* jump to current system time, use curent estimated frequency */
    	vt0 = curFileTime.QuadPart;

    } else {
    	/* calculate new frequency and estimate drift to the next second */
	vt1 = 20000000 + curFileTime.QuadPart;
	driftFreq = (estFreq * 20000000 / (vt1 - vt0));
	/* 
	 * Avoid too large drifts (only half of the current difference),
	 * that allows also be more accurate (aspire to the smallest tdiff),
	 * so then we can prolong calibration interval by tdiff < 100000
	 */
	driftFreq = timeInfo.curCounterFreq.QuadPart +
		(driftFreq - timeInfo.curCounterFreq.QuadPart) / 2;





	/* 
	 * Average between estimated, 2 current and 5 drifted frequencies,
	 * (do the soft drifting as possible)
	 */
	estFreq = (estFreq + 2 * timeInfo.curCounterFreq.QuadPart + 5 * driftFreq) / 8;
    }
    
    /* Avoid too large discrepancy from nominal frequency */
    if (estFreq > 1003*timeInfo.nominalFreq.QuadPart/1000) {
	estFreq = 1003*timeInfo.nominalFreq.QuadPart/1000;
	vt0 = curFileTime.QuadPart;
    } else if (estFreq < 997*timeInfo.nominalFreq.QuadPart/1000) {
	estFreq = 997*timeInfo.nominalFreq.QuadPart/1000;
	vt0 = curFileTime.QuadPart;
    } else if (vt0 != curFileTime.QuadPart) {
	/* 
	 * Be sure the clock ticks never backwards (avoid it by negative drifting)
	 * just compare native time (in 100-ns) before and hereafter using 
	 * new calibrated values) and do a small adjustment (short time freeze)
	 */
	LARGE_INTEGER newPerfCounter;
	Tcl_WideInt nt0, nt1;

	QueryPerformanceCounter(&newPerfCounter);
	nt0 = NativeCalc100NsTicks(timeInfo.fileTimeLastCall.QuadPart,
		timeInfo.perfCounterLastCall.QuadPart, timeInfo.curCounterFreq.QuadPart,
		newPerfCounter.QuadPart);
	nt1 = NativeCalc100NsTicks(vt0,
		curPerfCounter.QuadPart, estFreq,
		newPerfCounter.QuadPart);
	if (nt0 > nt1) { /* drifted backwards, try to compensate with new base */
	    /* first adjust with a micro jump (short frozen time is acceptable) */
	    vt0 += nt0 - nt1;
	    /* if drift unavoidable (e. g. we had a time switch), then reset it */
	    vt1 = vt0 - curFileTime.QuadPart;
	    if (vt1 > 10000000 || vt1 < -10000000) {
	    	/* larger jump resp. shift relative new file-time */
	    	vt0 = curFileTime.QuadPart;
	    }
	}
    }

    /* In lock commit new values to timeInfo (hold lock as short as possible) */
    EnterCriticalSection(&timeInfo.cs);

    /* grow calibration interval up to 10 seconds (if still precise enough) */
    if (tdiff < -100000 || tdiff > 100000) {
	/* too long drift - reset calibration interval to 1000 second */
	timeInfo.calibrationInterv = 1;
    } else if (timeInfo.calibrationInterv < 10) {
	timeInfo.calibrationInterv++;
    }

    timeInfo.fileTimeLastCall.QuadPart = vt0;
    timeInfo.curCounterFreq.QuadPart = estFreq;
    timeInfo.perfCounterLastCall.QuadPart = curPerfCounter.QuadPart;

    LeaveCriticalSection(&timeInfo.cs);
}
 
/*
 *----------------------------------------------------------------------