Numpy 数据精度

https://docs.scipy.org/doc/numpy-dev/user/basics.types.html

数据类型 描述 bool_ Boolean (True or False) stored as a byte int_ Default integer type (same as C long normally either int64 or int32) intc Identical to C int (normally int32 or int64) intp Integer used for indexing (same as C ssize_tnormally either int32 or int64) int8 Byte (-128 to 127) int16 Integer (-32768 to 32767) int32 Integer (-2147483648 to 2147483647) int64 Integer (-9223372036854775808 to 9223372036854775807) uint8 Unsigned integer (0 to 255) uint16 Unsigned integer (0 to 65535) uint32 Unsigned integer (0 to 4294967295) uint64 Unsigned integer (0 to 18446744073709551615) float_ Shorthand for float64. float16 Half precision float: sign bit, 5 bits exponent, 10 bits mantissa float32 Single precision float: sign bit, 8 bits exponent, 23 bits mantissa float64 Double precision float: sign bit, 11 bits exponent, 52 bits mantissa complex_ Shorthand for complex128. complex64 Complex number, represented by two 32-bit floats (real and imaginary components) complex128 Complex number, represented by two 64-bit floats (real and imaginary components)

单精度8位阶码，1位符号，剩下23位尾数，算出2的负23次方，得到0.00000011920928955078125
前面0有多少个，就表示能精确到那一位
双精度11位阶码，1位符号，剩下52位尾数，算出2的负52次方，得到0.00000000000000022204460492503130808472633361816
前面0有多少个，就表示能精确到那一位

参考文献
http://bbs.bccn.net/thread-316069-1-1.html
http://blog.csdn.net/qq_34312386/article/details/52454701
http://blog.sina.com.cn/s/blog_814e83d80101bgcf.html
https://zhidao.baidu.com/question/181927800.html