不能增加浮点变量的值
本文关键字:浮点变量 增加 不能 | 更新日期: 2023-09-27 17:54:28
我是c#新手,我不明白,为什么我的变量不想增加到大于16777215的值
我有代码:
float fullPerc = 100;
float bytesRead = 1;
long fileSize = 1;
ProgressBar pb1;
int blockSizeBytes = 0;
float counter = 0;
using (FileStream inFs = new FileStream(inFile, FileMode.Open))
{
fileSize = inFs.Length;
do
{
counter = counter + 1;
if (counter > 16777215) //&& counter < 16777230)
{
counter = counter + 10;
//Console.WriteLine(((counter + 10) /100));
}
count = inFs.Read(data, 0, blockSizeBytes);
offset += count;
outStreamEncrypted.Write(data, 0, count);
bytesRead += blockSizeBytes;
}
while (count > 0);
inFs.Close();
}
https://bitbucket.org/ArtUrlWWW/myfileencoderdecoder/src/f7cce67b78336636ef83058cd369027b0d146b17/FileEncoder/Encrypter.cs?at=master& fileviewer = file-view-default # encrypter.cs - 166
当计数器的值等于16777216时,变量增量counter = counter + 1;
的代码不起作用,但此代码
if (counter > 16777215) //&& counter < 16777230)
{
counter = counter + 10;
//Console.WriteLine(((counter + 10) /100));
}
是正常的
例如,如果我注释这个if
代码,我的counter
将增长到16777216值,并将停止在这个值。当该变量>=16777216时,该变量只会增加10。
为什么?
尾数溢出,结果导致精度损失。float
(或Single
)类型具有24位尾数(不超过16777216
):
让我们看看发生了什么:
private static String MakeReport(float value) {
return String.Join(" ", BitConverter
.GetBytes(value)
.Select(b => Convert.ToString(b, 2).PadLeft(8, '0')));
}
...
float f = 16777215;
// Mantissa (first 3 bytes) is full of 1's except the last one bit
// 11111111 11111111 01111111 01001011
Console.Write(MakeReport(f));
// Overflow! Presision loss
// 00000000 00000000 10000000 01001011
Console.Write(MakeReport(f + 1));
// Overflow! Presision loss
// 00000000 00000000 10000000 01001011
Console.Write(MakeReport(f + 2));
// Overflow! Presision loss
// 00000100 00000000 10000000 01001011
Console.Write(MakeReport(f + 10));
补救方法:不使用浮点数作为counter
,而使用整数:
int counter = 0;
为避免整数除法将value强制转换为double
float x = (float) ((((double)counter * blockSizeBytes) / fileSize) * fullPerc);