乱想数学

Posted 2020-10-21

In [6]: for x in xrange(1, 65): ...: print "power(2, {0})".format(x) , pow(2, x) ...: power(2, 1) 2 power(2, 2) 4 power(2, 3) 8 power(2, 4) 16 power(2, 5) 32 power(2, 6) 64 power(2, 7) 128 power(2, 8) 256 power(2, 9) 512 power(2, 10) 1024 power(2, 11) 2048 power(2, 12) 4096 power(2, 13) 8192 power(2, 14) 16384 power(2, 15) 32768 power(2, 16) 65536 power(2, 17) 131072 power(2, 18) 262144 power(2, 19) 524288 power(2, 20) 1048576 power(2, 21) 2097152 power(2, 22) 4194304 power(2, 23) 8388608 power(2, 24) 16777216 power(2, 25) 33554432 power(2, 26) 67108864 power(2, 27) 134217728 power(2, 28) 268435456 power(2, 29) 536870912 power(2, 30) 1073741824 power(2, 31) 2147483648 power(2, 32) 4294967296 power(2, 33) 8589934592 power(2, 34) 17179869184 power(2, 35) 34359738368 power(2, 36) 68719476736 power(2, 37) 137438953472 power(2, 38) 274877906944 power(2, 39) 549755813888 power(2, 40) 1099511627776 power(2, 41) 2199023255552 power(2, 42) 4398046511104 power(2, 43) 8796093022208 power(2, 44) 17592186044416 power(2, 45) 35184372088832 power(2, 46) 70368744177664 power(2, 47) 140737488355328 power(2, 48) 281474976710656 power(2, 49) 562949953421312 power(2, 50) 1125899906842624 power(2, 51) 2251799813685248 power(2, 52) 4503599627370496 power(2, 53) 9007199254740992 power(2, 54) 18014398509481984 power(2, 55) 36028797018963968 power(2, 56) 72057594037927936 power(2, 57) 144115188075855872 power(2, 58) 288230376151711744 power(2, 59) 576460752303423488 power(2, 60) 1152921504606846976 power(2, 61) 2305843009213693952 power(2, 62) 4611686018427387904 power(2, 63) 9223372036854775808 power(2, 64) 18446744073709551616 In [7]: # 4294967296 max mem In [8]: 4294967296 / 8 Out[8]: 536870912 In [9]: 4294967296 / 8 /1024 /1024 # MB Out[9]: 512 In [10]: 4294967296 /1024 /1024 # MB Out[10]: 4096 In [11]: 4294967296 /1024 /1024 / 1024 # GB Out[11]: 4 In [12]: # so 32bit computer supput 4GB mem In [13]: 18446744073709551616 / pow(1024, 3) # GB Out[13]: 17179869184L In [14]: 18446744073709551616 / 1024/ 1024/ 1024 # GB Out[14]: 17179869184L In [15]: 64 / 1 Out[15]: 64 In [16]: print("1"*64) 1111111111111111111111111111111111111111111111111111111111111111 In [17]: int("1"*64, 2) Out[17]: 18446744073709551615L In [18]: # 18446744073709551616 In [19]: # 18446744073709551615L In [20]: # so 64bit cpu 是近几年不会增大位数的CPU In [21]: # 内存通道问题 In [22]: # 多物理CPU, 4颗CPU 256G内存如何分配，通过主机的通道来分配 In [23]: 256 / 4 # 每通道配置内存最合适 Out[23]: 64