1 /* $Id: runlength.c,v 1.1 2010/02/07 14:07:25 fredette Exp $ */
2
3 /* libtme/runlength.c - run length: */
4
5 /*
6 * Copyright (c) 2010 Matt Fredette
7 * All rights reserved.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
17 * 3. All advertising materials mentioning features or use of this software
18 * must display the following acknowledgement:
19 * This product includes software developed by Matt Fredette.
20 * 4. The name of the author may not be used to endorse or promote products
21 * derived from this software without specific prior written permission.
22 *
23 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
24 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
25 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
26 * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
27 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
28 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
29 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
31 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
32 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
33 * POSSIBILITY OF SUCH DAMAGE.
34 */
35
36 #include <tme/common.h>
37 _TME_RCSID("$Id: runlength.c,v 1.1 2010/02/07 14:07:25 fredette Exp $");
38
39 /* includes: */
40 #include <tme/runlength.h>
41 #include <tme/misc.h>
42
43 /* this initializes runlength state: */
44 void
tme_runlength_init(struct tme_runlength * runlength)45 tme_runlength_init(struct tme_runlength *runlength)
46 {
47 unsigned long runlength_history_count;
48 tme_runlength_t runlength_value;
49
50 /* allocate the runlength history: */
51 runlength_history_count = runlength->tme_runlength_history_count;
52 assert (runlength_history_count > 0);
53 runlength->_tme_runlength_history = tme_new(tme_runlength_t, runlength_history_count);
54
55 /* set the initial runlength history sum: */
56 runlength_value = runlength->tme_runlength_value;
57 runlength->_tme_runlength_history_sum
58 = (((double) runlength_value)
59 * runlength->tme_runlength_history_count);
60
61 /* initialize the runlength history: */
62 do {
63 runlength->_tme_runlength_history[runlength_history_count - 1] = runlength_value;
64 } while (--runlength_history_count);
65 runlength->_tme_runlength_history_next = 0;
66 }
67
68 /* this sets the runlength cycles target: */
69 void
tme_runlength_target_cycles(struct tme_runlength * runlength,union tme_value64 cycles_elapsed_target_value64)70 tme_runlength_target_cycles(struct tme_runlength *runlength,
71 union tme_value64 cycles_elapsed_target_value64)
72 {
73 double two_to_the_thirtysecond;
74
75 /* make 2^32: */
76 two_to_the_thirtysecond = 65536 * (double) 65536;
77
78 /* set the target number of cycles to elapse during a run: */
79 runlength->_tme_runlength_cycles_elapsed_target
80 = ((cycles_elapsed_target_value64.tme_value64_uint32_hi
81 * two_to_the_thirtysecond)
82 + cycles_elapsed_target_value64.tme_value64_uint32_lo);
83 }
84
85 /* this updates the runlength: */
86 void
tme_runlength_update(struct tme_runlength * runlength)87 tme_runlength_update(struct tme_runlength *runlength)
88 {
89 double two_to_the_thirtysecond;
90 union tme_value64 cycles_elapsed;
91 tme_runlength_t runlength_value;
92 unsigned long runlength_history_next;
93 double runlength_history_sum;
94
95 /* make 2^32: */
96 two_to_the_thirtysecond = 65536 * (double) 65536;
97
98 /* get the number of cycles that elapsed during this run: */
99 cycles_elapsed = tme_misc_cycles();
100 (void) tme_value64_sub(&cycles_elapsed, &runlength->tme_runlength_cycles_start);
101
102 /* get a better length for this run: */
103 runlength_value
104 = (runlength->tme_runlength_value
105 * (runlength->_tme_runlength_cycles_elapsed_target
106 / ((cycles_elapsed.tme_value64_uint32_hi
107 * two_to_the_thirtysecond)
108 + cycles_elapsed.tme_value64_uint32_lo)));
109 if (__tme_predict_false(runlength_value == 0)) {
110 runlength_value += 1;
111 }
112
113 /* update the runlength history and sum: */
114 runlength_history_next = runlength->_tme_runlength_history_next;
115 runlength_history_sum
116 = ((runlength->_tme_runlength_history_sum
117 - runlength->_tme_runlength_history[runlength_history_next])
118 + runlength_value);
119 runlength->_tme_runlength_history[runlength_history_next] = runlength_value;
120 runlength->_tme_runlength_history_sum = runlength_history_sum;
121 if (runlength_history_next == 0) {
122 runlength_history_next = runlength->tme_runlength_history_count;
123 }
124 runlength->_tme_runlength_history_next = runlength_history_next - 1;
125
126 /* update the runlength value: */
127 runlength->tme_runlength_value
128 = (runlength_history_sum
129 / runlength->tme_runlength_history_count);
130 }
131