michael@0: /*
michael@0:  * Any copyright is dedicated to the Public Domain.
michael@0:  * http://creativecommons.org/licenses/publicdomain/
michael@0:  */
michael@0: 
michael@0: // Some tests regarding conversion to Float32
michael@0: assertEq(Math.fround(), NaN);
michael@0: 
michael@0: // Special values
michael@0: assertEq(Math.fround(NaN), NaN);
michael@0: assertEq(Math.fround(-Infinity), -Infinity);
michael@0: assertEq(Math.fround(Infinity), Infinity);
michael@0: assertEq(Math.fround(-0), -0);
michael@0: assertEq(Math.fround(+0), +0);
michael@0: 
michael@0: // Polyfill function for Float32 conversion
michael@0: var toFloat32 = (function() {
michael@0:     var f32 = new Float32Array(1);
michael@0:     function f(x) {
michael@0:         f32[0] = x;
michael@0:         return f32[0];
michael@0:     }
michael@0:     return f;
michael@0: })();
michael@0: 
michael@0: // A test on a certain range of numbers, including big numbers, so that
michael@0: // we get a loss in precision for some of them.
michael@0: for (var i = 0; i < 64; ++i) {
michael@0:     var p = Math.pow(2, i) + 1;
michael@0:     assertEq(Math.fround(p), toFloat32(p));
michael@0:     assertEq(Math.fround(-p), toFloat32(-p));
michael@0: }
michael@0: 
michael@0: /********************************************
michael@0: /* Tests on maximal Float32 / Double values *
michael@0: /*******************************************/
michael@0: function maxValue(exponentWidth, significandWidth) {
michael@0:     var n = 0;
michael@0:     var maxExp = Math.pow(2, exponentWidth - 1) - 1;
michael@0:     for (var i = significandWidth; i >= 0; i--)
michael@0:         n += Math.pow(2, maxExp - i);
michael@0:     return n;
michael@0: }
michael@0: 
michael@0: var DBL_MAX = maxValue(11, 52);
michael@0: assertEq(DBL_MAX, Number.MAX_VALUE); // sanity check
michael@0: 
michael@0: // Finite as a double, too big for a float
michael@0: assertEq(Math.fround(DBL_MAX), Infinity);
michael@0: 
michael@0: var FLT_MAX = maxValue(8, 23);
michael@0: assertEq(Math.fround(FLT_MAX), FLT_MAX);
michael@0: assertEq(Math.fround(FLT_MAX + Math.pow(2, Math.pow(2, 8 - 1) - 1 - 23 - 2)), FLT_MAX); // round-nearest rounds down to FLT_MAX
michael@0: assertEq(Math.fround(FLT_MAX + Math.pow(2, Math.pow(2, 8 - 1) - 1 - 23 - 1)), Infinity); // no longer rounds down to FLT_MAX
michael@0: 
michael@0: /*********************************************************
michael@0: /******* Tests on denormalizations and roundings *********
michael@0: /********************************************************/
michael@0: 
michael@0: function minValue(exponentWidth, significandWidth) {
michael@0:     return Math.pow(2, -(Math.pow(2, exponentWidth - 1) - 2) - significandWidth);
michael@0: }
michael@0: 
michael@0: var DBL_MIN = Math.pow(2, -1074);
michael@0: assertEq(DBL_MIN, Number.MIN_VALUE); // sanity check
michael@0: 
michael@0: // Too small for a float
michael@0: assertEq(Math.fround(DBL_MIN), 0);
michael@0: 
michael@0: var FLT_MIN = minValue(8, 23);
michael@0: assertEq(Math.fround(FLT_MIN), FLT_MIN);
michael@0: 
michael@0: assertEq(Math.fround(FLT_MIN / 2), 0); // halfway, round-nearest rounds down to 0 (even)
michael@0: assertEq(Math.fround(FLT_MIN / 2 + Math.pow(2, -202)), FLT_MIN); // first double > FLT_MIN / 2, rounds up to FLT_MIN
michael@0: 
michael@0: assertEq(Math.fround(-FLT_MIN), -FLT_MIN);
michael@0: 
michael@0: assertEq(Math.fround(-FLT_MIN / 2), -0); // halfway, round-nearest rounds up to -0 (even)
michael@0: assertEq(Math.fround(-FLT_MIN / 2 - Math.pow(2, -202)), -FLT_MIN); // first double < -FLT_MIN / 2, rounds down to -FLT_MIN
michael@0: 
michael@0: reportCompare(0, 0, "ok");