On Fri, 2 Jun 2006 17:03:11 -0500, "Bo Peng" <ben.bob@gmail.com> wrote:
Dear list,
I am using dynamic_bitset to store a sequence of random 0/1. The program generates repeatedly 32bit random numbers and assign the result to a dynamic_bitset.
for(UINT i=0; i < m_N; ++i) { if(bit == block) // generate a block { ri = rng().randInt(m_max); bit = 0; } if((ri >> bit) & 0x1) succ.set(i); bit++; } When I profile this program, I surprisingly find out that succ.set(i) uses >50% of the execution time. Is there anyway I can assign block by block to dynamic_bitset, or assign sequentially so the position of i does not have to be calculated each time?
Hi, you code looks suspect to me. Are you aware it actually yields m_N bits rather than m_N blocks? Also, I'll assume the dynamic_bitset is sized in advance. Sticking to the problem, there are many alternative codings; in particular you could use the iterator-based version of append, after creating a little iterator class for the random integers (please, ignore from_block_range() :-)). If that's not suitable for you might try this: typedef UINT block_type; boost::dynamic_bitset<block_type> succ; /* no resizing needed */ // (assuming m_N is a multiple of the UINT width, i.e. 32) for(UINT i=1; i <= m_N / (block + 1); ++i) { block_type b = /*random...*/; succ.append(b); } Please, let us know if this helped. Cheers, Gennaro. -- Genny.