Thread: Need help with std::bad_alloc

Hi,

I have been working on c++ project. My project is big in size. I have added new algorithm to it. The program goes upto few clock cycles and after that it cannot dispatch more instruction and so it goes into timeout(defined in program) or it gives me strange error that says "terminate called after throwing an instance of 'std::bad_alloc' what(): ".

I am using c++ vector here. My program works fine without the added new algorithm but with the added part, I am not sure if has memory allocation problem or not. However I think my algorithm is correct. I also tried the program by removing some portion of that algorithm and it goes upto more instructions than before and then goes in timeout. I really think it is a memory allocation problem, but I am not sure how to solve it as I am still learning C++. I use g++ compiler on linux.

If anybody has any idea, Please let know. Any help is greatly appreciated.

Thank You.

So, bad_alloc is thrown by the standard containers (like vector) when you are out of memory. What that means for your code I can't say.

Hi,

I understood that I my algorithm is trying to allocate more memory. I tried to reduce the input and it works fine. But my project is really big and I am not sure how to solve this part. Do I need more memory or is there any better way to allocate lesser memory. I a really lost here. My code is really big but I can show a part of my algorithm here.

Code:

odescnd_index[disp_context_id] = (scnd_index[disp_context_id] + (contexts[disp_context_id].ROB.size()-1)) % contexts[disp_context_id].ROB.size();
			//for(scnd_index[disp_context_id]=(contexts[disp_context_id].ROB_head); scnd_index[disp_context_id]!= contexts[disp_context_id].ROB_tail; scnd_index[disp_context_id]=(scnd_index[disp_context_id]+1))
			unsigned int num_searched = 0, prev_index = 0;
					while(num_searched<contexts[disp_context_id].ROB_num)
							{
								ROB_entry *prev_inst;
							    is = &contexts[disp_context_id].ROB[scnd_index[disp_context_id]];
							  if(is->dispatched == 0){
							    if(rs->src_physreg[0] == is->physreg){
							    	contexts[disp_context_id].ROB[contexts[disp_context_id].ROB_tail].prev_depend_ctr.push_back(&contexts[disp_context_id].ROB[scnd_index[disp_context_id]]);
							    	contexts[disp_context_id].ROB[scnd_index[disp_context_id]].depend_ctr.push_back(&contexts[disp_context_id].ROB[contexts[disp_context_id].ROB_tail]);
							    	if(is->depend_flag != 0){
							    		prev_inst = is;
							    		while(!prev_inst->prev_depend_ctr.empty()){
							    			prev_inst = prev_inst->prev_depend_ctr[0];
							    			prev_inst->depend_ctr.push_back(&contexts[disp_context_id].ROB[contexts[disp_context_id].ROB_tail]);
							    			rs->depend_flag++;
							    		}
							    	}
							    	rs->depend_flag++;
							    }
							    else if(rs->src_physreg[1] == is->physreg){
							    	contexts[disp_context_id].ROB[contexts[disp_context_id].ROB_tail].prev_depend_ctr.push_back(&contexts[disp_context_id].ROB[scnd_index[disp_context_id]]);
							        contexts[disp_context_id].ROB[scnd_index[disp_context_id]].depend_ctr.push_back(&contexts[disp_context_id].ROB[contexts[disp_context_id].ROB_tail]);
							        if(is->depend_flag != 0){
							        	prev_inst = is;
							        	while(!prev_inst->prev_depend_ctr.empty()){
							        		prev_inst = prev_inst->prev_depend_ctr[0];
							        		prev_inst->depend_ctr.push_back(&contexts[disp_context_id].ROB[contexts[disp_context_id].ROB_tail]);
							        		rs->depend_flag++;
							        	}
							        }
							        rs->depend_flag++;
							    }
							  }
							    num_searched++;
							    scnd_index[disp_context_id] = (scnd_index[disp_context_id] + (contexts[disp_context_id].ROB.size()-1)) % contexts[disp_context_id].ROB.size();
							 }

In above algorithm, I have "depend_ctr" and "prev_depend_ctr" are two vectors that I have declared to the Class "ROB_entry". ROB is a vector of "ROB_entry"ies and each ROB_entry has one "depend_ctr" and "prev_depend_ctr" and they hold pointer to other ROB_entries. I am not sure if I can add index of that entry instead of pointer. But this works with small input upto arround 1000 instructions but I really need it for much more instructions.

If anybody knows better solution to it, please let me know. I really appreciate any help, as I need to finish this week.

Thank You.