if(( lenDst < 512)||( MIN(Src1Len,Src2Len) <64 ))
because the FFT-based convolution would be faster when thelength data islarge enough. But as you see, the "critical point" isavalue byempirical test. Around the critical point, the performance advantagemay be wobbles.
Do you alwayscaculate the convolution of the source buffer is large and the second one keep 64 sowant to use direct algorithm?
just for your reference, the Direct Convolution is supported by MKL(IPP sister library) also.
For example, y=x(*)h, MKL call is like
status = vslsConvExec1D(task, h,inch, x,incx, y,incy);
For more information, please see <<>>>