我正在尝试决定是否需要bigint lib或正常的js数字就足够了。我想将文件大小除以块大小（最大为100GB）以获得我有多少块：HTMLWidgets.widget({
name: 'IMposterior',
type: 'output',
factory: function(el, width, height) {
// TODO: define shared variables for this instance
return {
renderValue: function(opts) {
console.log("MME: ", opts.MME);
console.log("threshold: ", opts.threshold);
console.log("prob: ", opts.prob);
console.log("colors: ", opts.colors);
var margin = {left:50,right:50,top:40,bottom:0};
var xMax = opts.x.reduce(function(a, b) {
return Math.max(a, b);
});
var yMax = opts.y.reduce(function(a, b) {
return Math.max(a, b);
});
var xMin = opts.x.reduce(function(a, b) {
return Math.min(a, b);
});
var yMin = opts.y.reduce(function(a, b) {
return Math.min(a, b);
});
var y = d3.scaleLinear()
.domain([0,yMax])
.range([height,0]);
var x = d3.scaleLinear()
.domain([xMin,xMax])
.range([0,width]);
var yAxis = d3.axisLeft(y);
var xAxis = d3.axisBottom(x);
var area = d3.area()
.x(function(d,i){ return x(opts.x[i]) ;})
.y0(height)
.y1(function(d){ return y(d); });
var svg = d3.select(el).append('svg').attr("height","100%").attr("width","100%");
var chartGroup = svg.append("g").attr("transform","translate("+margin.left+","+margin.top+")");
chartGroup.append("path")
.attr("d", area(opts.y));
chartGroup.append("g")
.attr("class","axis x")
.attr("transform","translate(0,"+height+")")
.call(xAxis);
},
resize: function(width, height) {
// TODO: code to re-render the widget with a new size
}
};
}
});
。我记得js在精确划分方面存在问题。
我在结果中获得howManyChunks = Math.ceil(fileSize/chunkSize)而不是x+1 = Math.ceil(x.00000000000..01)的机会是什么？
答案 0 :(得分：0)
我决定尝试一下。正常的js数字的精度在3-4PB文件大小附近开始不够。因此在Firefox中，js整数的精度约为55位。我想这可能因浏览器而异，但我需要这个用于nodejs。
console.log("start");
var B = 8;
var KB = 1024*B;
var MB = 1024*KB;
var GB = 1024*MB;
var TB = 1024*GB;
var PB = 1024*TB;
var EB = 1024*PB;
var maxBits = 4 * PB;
var bitSteps = 100 * TB;
var maxChunkSize = 333 * B;
for (var bits = 0; bits <= maxBits; bits += bitSteps)
for (var chunkSize = 1; chunkSize <= maxChunkSize; ++chunkSize) {
var calculatedChunkCount = Math.ceil(bits/chunkSize);
var calculatedBits = calculatedChunkCount * chunkSize;
var difference = calculatedBits - bits;
var error = difference>= chunkSize || difference<0;
if (error)
console.log({
chunkSize: chunkSize,
calculatedChunkCount: calculatedChunkCount,
bits: bits,
calculatedBits: calculatedBits,
difference: difference
});
}
console.log("end");
输出：
{ chunkSize: 97, calculatedChunkCount: 290180388361501, bits: 28147497671065600, calculatedBits: 28147497671065596, difference: -4 }
{ chunkSize: 1579, calculatedChunkCount: 20611490932343, bits: 32545544182169600, calculatedBits: 32545544182169596, difference: -4 }
我会在晚上启动并行nodejs脚本以确保，但我认为在0 - 100GB范围内精度足够。
根据另一个答案：https://stackoverflow.com/a/2803010/607033 js整数精确到53位。所以这个除法限制可能接近那个值，可能会低一些。