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fix overflow problem if timer res is low; cleaned up in general; use RingBuf for averaging

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This was SVN commit r508.
This commit is contained in:
janwas 2004-06-14 13:29:23 +00:00
parent 7fb1f4892e
commit 952ec353fb
1 changed files with 27 additions and 22 deletions
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49
source/lib/timer.cpp
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@ -19,6 +19,7 @@
#include "lib.h"
#include "timer.h"
#include "adts.h"
#include <math.h>
@ -99,28 +100,35 @@ int fps = 0;
void calc_fps()
{
// history buffer - smooth out slight variations
#define H 10 // # buffer entries
static float fps_sum = 0; // sum of last H frames' cur_fps
static float fps_hist[H]; // last H frames' cur_fps
// => don't need to re-average every time
static uint head = 0; // oldest entry in fps_hist
// must be unsigned, b/c we do (head-1)%H
RingBuf<float, 16> samples;
// get elapsed time [s] since last frame; approximate current fps
// get elapsed time [s] since last update
static double last_t;
double t = get_time();
const double t = get_time();
const double dt = t - last_t;
// (in case timer resolution is low): count frames until
// timer value has changed "enough".
static uint num_frames = 1;
if(dt < 1e-3)
// bonus: if FPS > 1000, updates are slowed down a few frames.
{
num_frames++;
return;
}
// dt is big enough => we will update.
// calculate approximate current FPS (= 1 / elapsed time per frame).
float cur_fps = 30.0f; // start value => history converges faster
if(last_t != 0.0)
cur_fps = 1.0f / (float)(t-last_t); // = 1 / elapsed time
cur_fps = 1.0f / (float)dt * num_frames;
num_frames = 1; // reset for next time
last_t = t;
if (cur_fps > 1e+6) // Avoid undesirable infinities if some frames
return; // were rendered in no time
// calculate fps activity over 3 frames (used below to prevent fluctuation)
// -1: decreasing, +1: increasing, 0: neither or fluctuating
float h1 = fps_hist[(head-1)%H]; // last frame's cur_fps
float h2 = fps_hist[(head-2)%H]; // 2nd most recent frame's cur_fps
const float h1 = samples[-1]; // last frame's cur_fps
const float h2 = samples[-2]; // 2nd most recent frame's cur_fps
int trend = 0;
if(h2 > h1 && h1 > cur_fps) // decreasing
@ -135,17 +143,14 @@ void calc_fps()
return; // yes: don't update fps_hist/fps
ignored = 0; // either value ok, or it wasn't a fluke - reset counter
// remove oldest cur_fps value in fps_hist from the sum
// and add cur_fps; also insert cur_fps in fps_hist
fps_sum -= fps_hist[head];
fps_sum += (fps_hist[head] = cur_fps);
head = (head+1)%H;
// add new sample and average
samples.push_back(cur_fps);
const double sum_fps = std::accumulate(samples.begin(), samples.end(), 0.0);
const double avg_fps = sum_fps / (int)samples.size();
// update fps counter if update threshold is exceeded
const float avg_fps = fps_sum / H;
const float d_avg = avg_fps-fps;
const float d_avg = (float)(avg_fps-fps);
const float max_diff = fminf(5.f, 0.05f*fps);
if((trend > 0 && (avg_fps > fps || d_avg < -4.f)) || // going up, or large drop
(trend < 0 && (avg_fps < fps || d_avg > 4.f)) || // going down, or large raise
(fabs(d_avg) > max_diff)) // significant difference