Hi, the following code: double fStart = 31337; double fEnd = 65536; double fStep = fStart - fEnd; fStep /= 512; for (int i = 0; i < 512; i++) { std::cout << std::hex << boost::hash<double>()(fStart + i * fStep) << std::endl; } leads to the output of surprisingly regular hash values (see end of mail). This seems to occur mainly if a power of two number of points is sampled equidistantly within an interval. Especially since some hash table implementations (e.g. intel's threading building blocks) only use the last few bits to determine the bucket, this can lead to very bad caching behaviour for the rather common case of regularly sampled points (equidistant samplings of power of 2 are e.g. common in computer graphics and numerical algorithms). Are you aware of this? Would you consider it a bug? Best regards, Kai Schroeder Output of code using Boost 1.48 (similar behaviour can be observed for other start and end values and other power of 2 step counts): ff9f20000000000f e5042f900000000f 52f13f200000000f 297ac8b00000000f 48721e400000000f 2f9b8dd00000000f 3df0b1600000000f d19cf2f00000000f 9201c800000000f 9409aa100000000f 7cb3fba00000000f d7a42b300000000f b15982c00000000f 5f7900500000000f e0ba85e00000000f 255ee5700000000f cec119000000000f 955bd6900000000f 6a58f4200000000f 843a37b00000000f 590797400000000f 7e8db4d00000000f 1721b6600000000f 37acf9f00000000f df5f65800000000f 88b1a5100000000f 494a0a00000000f bb1082300000000f 1ea62bc00000000f ...