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handwritten asm.js code for logsumexp
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// MIT License. Copyright (c) 2016 Hajime Senuma. | |
/** | |
* asm.js module for logsumexp | |
*/ | |
function asmModule(stdlib, foreign, heap) { | |
'use asm'; | |
var exp = stdlib.Math.exp; | |
var log = stdlib.Math.log; | |
var f32heap = new stdlib.Float32Array(heap); | |
/** | |
* Returns the largest number of one or more 32-bit floats. | |
* | |
* @param {number} valueP - byte offset to the 32-bit float sequence. | |
* @param {number} len - length of the float sequence. | |
* If this value is less than 1, the behavior is undefined. | |
* @returns {number} - 64-bit float (not 32-bit) | |
*/ | |
function maxFloat32(valueP, len) { | |
// Type annotations | |
valueP = valueP | 0; | |
len = len | 0; | |
// Local variables | |
var p = 0; | |
var end = 0; | |
var v = 0.0; | |
var result = 0.0; | |
// Main | |
p = valueP; | |
end = (valueP + (len << 2)) | 0; | |
result = +f32heap[p >> 2]; | |
p = (p + 4) | 0; | |
for (; (p | 0) < (end | 0); p = (p + 4) | 0) { | |
v = +f32heap[p >> 2]; | |
if (v >= result) { | |
result = v; | |
} | |
} | |
return +result; | |
} | |
/** | |
* Returns the logsumexp of one or more 32-bit floats. | |
* | |
* @param {number} valueP - byte offset to the 32-bit float sequence. | |
* @param {number} len - length of the float sequence. | |
* If this value is less than 1, the behavior is undefined. | |
* @returns {number} - 64-bit float (not 32-bit) | |
*/ | |
function logsumexp(valueP, len) { | |
// Type annotations | |
valueP = valueP | 0; | |
len = len | 0; | |
// Local variables | |
var p = 0; | |
var end = 0; | |
var v = 0.0; | |
var maxValue = 0.0; | |
var result = 0.0; | |
// Main | |
maxValue = +maxFloat32(valueP, len); | |
p = valueP; | |
end = (valueP + (len << 2)) | 0; | |
for (; (p | 0) < (end | 0); p = (p + 4) | 0) { | |
v = +f32heap[p >> 2]; | |
// exp(-20) = 2.06e-9, machine epsilon for float32 = 5.96e-08 | |
if (v - maxValue > -16.0) { | |
result = +(result + +exp(v - maxValue)); | |
} | |
} | |
return +(maxValue + +log(result)); | |
} | |
return { | |
maxFloat32: maxFloat32, | |
logsumexp: logsumexp | |
}; | |
} |
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