my text file name is doubledata.bin. It is quite a large file, but too large. data in it is like: 12.3453<tab>0.4065<tab>88.3454 etc. I like to read these files as fast as possible into memory arrays. any code to do that?.

Things would go much much faster if the data was stored purely as binary data (i.e. the raw bytes) rather than as a text file. The tabs also screw everything up. If it was the bytes themselves, you'd just use fread from cstdio and read thousands of bytes at a time directly into the array.

But that's not what you have, so I imagine you would just use the >> operator over and over again. It's much slower, but it'll get the job done.