It checks for the 0 case. Otherwise it passes the operation directly onto BLAS and assumes that BLAS handles the special cases efficiently.
Barry Here's the thing. Even if the BLAS implementation provided by the vector did not handle the special cases if we wrote a do/for loop directly to handle the special case it may still not be faster than then the BLAs since the BLAS may be tuned much better then the code the compiler can generate, plus the cost of AXPY is essentially the cost of the loads and stores not the multiply adds, eliminating the multiplies might not save you much. On Sun, 12 Aug 2007, John R. Wicks wrote: > It seems that the only way to add two vectors is to use VecAXPY(x,1,y); > likewise, to subtract one must call VecAXPY(x,-1,y). Are these routines > optimized to recognize these special cases to avoid the extraneous scalar > multiplications? > >
