float16-simulator.js/index.html at gh-pages · Oletus/float16-simulator.js · GitHub

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<html>
<head>
<title>Calculator that simulates floating-point numbers at the specified precision</title>
<script src="mediump-float.js"></script>
<script>
var ctx;
var logText = '';
var cachedA, cachedB;

var changebits = function() {
    mantissaShow.textContent = mantissaBits.value;
    exponentShow.textContent = exponentBits.value;
    var mb = parseInt(mantissaBits.value);
    var eb = parseInt(exponentBits.value);
    ctx = new FloatContext(mb, eb, false, true);
    // Note: lowp defines precision in absolute terms. So if the maximum exponent is too great,
    // the maximum value that can be represented does not have the required absolute precision.
    // This is likely just a bug in the spec, though.
    lowp.style.display = (mb >= 8 && eb >= 2 && maxNormalExponent(eb) <= (mb + 1) - 8) ? 'inline' : 'none';
    mediump.style.display = (mb >= 10 && eb >= 5) ? 'inline' : 'none';
    highp.style.display = (mb >= 16 && eb >= 8) ? 'inline' : 'none';
    ieee.style.display = (mb == 23 && eb == 8) ? 'inline' : 'none';
    shaderPrecisionFormat.textContent = JSON.stringify(ctx.getShaderPrecisionFormat());
    cachedA = undefined;
    cachedB = undefined;
    showOperands();
};

var addOpButtons = function(parent) {
    var fnNames = FloatContext.functions1;
    for (var i = 0; i < fnNames.length; ++i) {
        (function(fnName) {
            var btn = document.createElement('input');
            btn.type = 'button';
            btn.value = fnName;
            btn.onclick = function() {
                var a = parseFloat(operandA.value);
                var result = ctx[fnName](a);
                log(fnName, a, result);
                operandA.value = result;
            }
            parent.appendChild(btn);
        })(fnNames[i]);
    }
    parent.appendChild(document.createElement('br'));
    var fnNames = FloatContext.functions2;
    for (var i = 0; i < fnNames.length; ++i) {
        (function(fnName) {
            var btn = document.createElement('input');
            btn.type = 'button';
            btn.value = fnName;
            btn.onclick = function() {
                var a = parseFloat(operandA.value);
                var b = parseFloat(operandB.value);
                var result = ctx[fnName](a, b);
                log(fnName, a + ', ' + b, result);
                operandA.value = result;
                showOperands();
            }
            parent.appendChild(btn);
        })(fnNames[i]);
    }
};

var log = function(fnName, args, result) {
    var fnLog = fnName + "(" + args + ") = " + result + (ctx.isSubnormal(result) ? ' (subnormal)' : '');
    console.log(ctx.getSpecString());
    console.log(fnLog);
    logText = ctx.getSpecString() + ':\n' + fnLog + '\n' + logText;
    logElement.textContent = logText;
};

var start = function() {
    changebits();
    addOpButtons(document.getElementById('buttons'));
    window.setInterval(showOperands, 100);
};

var showOperand = function(a, parent, binary) {
    if (isNaN(a)) {
        parent.innerHTML = 'NaN (' + ctx.nanBitString() + ')';
        return;
    }
    parent.innerHTML = "";
    var sign = document.createElement('span');
    var exp = document.createElement('span');
    var expBits = document.createElement('span');
    var mantissa = document.createElement('span');
    sign.classList.add('signBit');
    exp.classList.add('exponent');
    expBits.classList.add('exponentBits');
    mantissa.classList.add('mantissaBits');
    var elements = [sign, exp, expBits, mantissa];
    for (i = 0; i < elements.length; ++i) {
        if (binary) {
            elements[i].classList.add('binary');
        } else {
            elements[i].classList.add('decimal');
        }
    }

    var parts = ctx.toBitStrings(a);

    sign.textContent = parts.sign;
    parent.appendChild(document.createTextNode('(-1)'));
    parent.appendChild(sign);

    if (binary) {
        parent.appendChild(document.createTextNode(' * 10'));
        expBits.textContent = parts.exponent;
        exp.appendChild(expBits);
        exp.appendChild(document.createTextNode(' - ' + parts.exponentBias));
    } else {
        parent.appendChild(document.createTextNode(' * 2'));
        exponent = parseInt(parts.exponent, 2) - parseInt(parts.exponentBias, 2);
        expBits.textContent = exponent;
        exp.appendChild(expBits);
    }
    parent.appendChild(exp);

    parent.appendChild(document.createTextNode(' * ' + (parts.isZero ? '0' : '1') + '.'));
    if (binary) {
        mantissa.textContent = parts.mantissa;
    } else {
        var mantissaStr = String(parseInt(parts.mantissa, 2) / parts.possibleMantissas);
        if (mantissaStr.length < 3) {
            mantissaStr = '0';
        } else {
            mantissaStr = mantissaStr.substring(2);
        }
        mantissa.textContent = mantissaStr;
    }
    parent.appendChild(mantissa);
};

var loadOperands = function() {
    var a = parseFloat(operandA.value);
    var result = ctx.fr(a);
    log("LOAD", a, result);
    operandA.value = result;
    var b = parseFloat(operandB.value);
    var result = ctx.fr(b);
    if (b !== a) {
        log("LOAD", b, result);
    }
    operandB.value = result;
    showOperands();
};

var showOperands = function() {
    var a = parseFloat(operandA.value);
    if (a !== cachedA) {
        showOperand(a, aBreakdown, true);
        showOperand(a, aDecimalBreakdown, false);
        cachedA = a;
    }
    var b = parseFloat(operandB.value);
    if (b !== cachedB) {
        showOperand(b, bBreakdown, true);
        showOperand(b, bDecimalBreakdown, false);
        cachedB = b;
    }
};

</script>
<style>
body {
    background: #ddd;
}
.container {
    width: 1000px;
    margin: auto;
}
.signBit, .exponent {
    vertical-align: super;
    font-size: 70%;
}
.signBit.binary, .exponentBits.binary, .mantissaBits.binary {
    background-color: #fa8;
}
.signBit.decimal, .exponentBits.decimal, .mantissaBits.decimal {
    background-color: #8fa;
}
.separator {
    display: inline-block;
    text-align: center;
    width: 4em;
}
.section {
    background: #fff;
    padding: 1em;
    margin: 1em 0;
    border-radius: 5px;
}
.section h2 {
    margin-top: 0;
}
</style>
</head>
<body onload="start()">
<div class="container">
<h1>Mediump float calculator</h1>
<h2>i.e. your floating-point computation results may vary</h2>
<p>This page implements a crude simulation of how floating-point calculations could be performed
on a chip implementing n-bit floating point arithmetic. It does not model any specific chip, but
rather just tries to comply to the OpenGL ES shading language spec. Subnormal numbers are flushed to zero.
</p>
<p>For more information, see
<a href="http://en.wikipedia.org/wiki/Half-precision_floating-point_format">
the Wikipedia article on the half-precision floating point format</a>.
</p>
<div class="section">
<h2>Float settings</h2>
Mantissa bits:
<input type="range" id="mantissaBits" min="5" max="23" value="10" onchange="changebits()"></input>
<span id="mantissaShow"></span><br>
Exponent bits:
<input type="range" id="exponentBits" min="2", max="8" value="5" onchange="changebits()"></input>
<span id="exponentShow"></span><br>
<p style="font-weight: bold;">
GLSL precision:
<span id="lowp" style="background-color: #faa;">lowp criteria fulfilled</span>
<span id="mediump" style="background-color: #fad;">mediump criteria fulfilled</span>
<span id="highp" style="background-color: #daf;">ES 1.00 highp criteria fulfilled</span>
<span id="ieee" style="background-color: #adf;">ES 3.00 highp criteria fulfilled</span>
</p>
<p>
WebGL getShaderPrecisionFormat would return: <span id="shaderPrecisionFormat"></span>
</p>
</div>

<div class="section">
<h2>Calculator</h2>
<p>
Operand A:
<input type="number" id="operandA" value="0"></input>
&#8776; binary <span id="aBreakdown" class="breakdown"></span><span class="separator"> = </span><span id="aDecimalBreakdown"></span>
</p>
<p>
Operand B:
<input type="number" id="operandB" value="0"></input>
&#8776; binary <span id="bBreakdown" class="breakdown"></span><span class="separator"> = </span><span id="bDecimalBreakdown"></span>
</p>
<p>
</p>
<div id="buttons">
<input type="button" value="LOAD" onclick="loadOperands()"></input>
</div>
</div>

<h2>Log</h2>
<pre id="logElement">
</pre>
</div>
</body>
</html>