Hi Pearu,

Btw, does anybody know an efficient way how to test if an integer is a power-of-two in C? Currently djbfft wrapper uses switch (n) { case 2:;case 4:;... case 8192: .. } but there must be a better way.

Fooling around a bit, I think the construction int foo(int n) { int ok = 1; if ( n == 1 || n == 2 || n == 4 || n == 8 ); else ok = 0; return ok; } produces the best looking assembly here. gcc optimizes the case statement without knowing that: 1) there will usually be a match, 2) it should be faster for small numbers than large numbers. That said, it probably doesn't matter much. For the curious the assembler looks like : foo: pushl %ebp movl %esp, %ebp subl $4, %esp movl $1, -4(%ebp) cmpl $1, 8(%ebp) je .L4 cmpl $2, 8(%ebp) je .L4 cmpl $4, 8(%ebp) je .L4 cmpl $8, 8(%ebp) je .L4 movl $0, -4(%ebp) .L4: movl -4(%ebp), %eax leave ret Just how I would do it. Extremely unusual, really. Chuck _______________________________________________ Scipy-dev mailing list Scipy-dev@scipy.net http://www.scipy.net/mailman/listinfo/scipy-dev