dmitrey schrieb: > Hi all, > I expected to have some speedup via using ldexp or multiplying an > array by a power of 2 (doesn't it have to perform a simple shift of > mantissa?), but I don't see the one. > > # Let me also note - > # 1) using b = 2 * ones(N) or b = zeros(N) doesn't yield any speedup > vs b = rand() > # 2) using A * 2.0 (or mere 2) instead of 2.1 doesn't yield any > speedup, despite it is exact integer power of 2. > On recent processors multiplication is very fast and takes 1.5 clock cycles (float, double precision), independent of the values. There is very little gain by using bit shift operators.
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