only time step of decode ldpc
test time of ldpc.bp_decode
test step time of ldpc::bp_decode
{// 1.2d, 0.13r
	// Step 0: init, 2ms
	for( iter < max_iters )	// 34
	{
		// Step 1: check to variable nodes, 32d / 3r
		for( j<ncheck )
		{
			for( sumX2(j) )	//
			for( sumX2(j) )	//
			for( sumX2(j) )	//
		}

		// Step 2: variable to check nodes, 6d / 1r
		for( i<nvar )
		{// differential update
			for( sumX1(i) )	//
			for( sumX1(i) )	//
		}

		// Step 3: check, 0
		for( j<ncheck )
			for( sumX2(j) )
	}
	return iter;
}
note: d-debug, r-release, time unit is second(s)
revert code ldpc, remove timer