chunks of an Uint8Array

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allObjects

NICE! --- me: ddddoooohhhh (: ... LOL...

That's where implicit - wishful - typing by variable naming (trap) kicks in... the 'wrong' name has been chosen for the variable: buffer is not a buffer because it is called so... ;(

I made a rough performance test, and it shows that slice is still about 6 times slower (even with some optimization / moving the var s out of loop)... memory is for sure contributing to the time aspect... - you can directly run the attached .html file by just clicking on the link. Test on Espruino still pending.

<html><head><title>typedBuffedSliced</title></head>
<body><h3>typedBuffedSliced</h3>
<button onclick="exec()">exec()</button>
<script>
var C = {
 OLED_WIDTH                 : 128,
 OLED_CHAR                  : 0x40,
 OLED_CHUNK                 : 128
}, WIDTH = 128, HEIGHT = 64;
function exec() {
  var buf = new Uint8Array((WIDTH*HEIGHT) / 8), bLen = buf.length;
  var chunk = new Uint8Array(C.OLED_CHUNK+1), cLen = chunk.length;
  console.log("buf: " + bLen + " - chunk: " + cLen);
  chunk[0] = C.OLED_CHAR;
  var p, pe, c1, t10, t11, slice, c2, t20, t21, cL = C.OLED_CHUNK;
  for (p=0; p < bLen; p += C.OLED_CHUNK) { pe = p + C.OLED_CHUNK;
    t10 = new Date().getTime(); for (c1 = 0; c1 < 100000; c1++) {
      chunk.set(new Uint8Array(buf.buffer,p,cL), 1);
    } t11 = new Date().getTime();
    t20 = new Date().getTime(); for (c2 = 0; c2 < 100000; c2++) {
      chunk.set(buf.slice(p, pe), 1);
    } t21 = new Date().getTime();
    console.log(p+"-"+(pe)+": " + ((t21 - t20) / (t11 - t10)));
  }
}
</script>
<pre>
Console:
buf: 1024 - chunk: 129
0-128: 4.375
128-256: 5.529411764705882
256-384: 7.142857142857143
384-512: 7.142857142857143
512-640: 7.846153846153846
640-768: 5.875
768-896: 6.928571428571429
896-1024: 7.615384615384615
</pre>
</body>
</html>

PS: updated - (line 18 had buf.buf and passing undefined which did speed it up to factor 2)

2 Attachments

typedBuffedSliced.html

chunks of an Uint8Array

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