yes, it adds some memoery usage, but doing the math i found that it isnt too much, <div><br></div><div>for the 8000x8000 problem, each string should be in the worst case length 21 (for example string s = "Ld0x1d2x3d4x5d6x7d8x9" ), assuming std::string is 1 byte per length unit:</div>
<div>stringMemory <= 21 bytes * 64M <= 1344Mbytes <= 1.3GB</div><div><br></div><div>i was considering the equivalent situation but for the expressions, which now are 64M smaller ones compared to 8000 bigger ones from before</div>
<div>could it be that they use so much memory?</div><div><br><br><div class="gmail_quote">On Wed, Oct 20, 2010 at 1:27 PM, James Jackson <span dir="ltr"><<a href="mailto:james.jackson@cern.ch">james.jackson@cern.ch</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">If I understand correctly, previously you were storing N strings, now you are storing N^2. This is 64M strings, as opposed to 8000. This might account for at least some of the memory!<br>
<br>
Regards,<br>
James<br>
<div><div></div><div class="h5"><br>
On 20 Oct 2010, at 16:45, Cristobal Navarro <<a href="mailto:axischire@gmail.com">axischire@gmail.com</a>> wrote:<br>
<br>
> Hello everybody,<br>
><br>
> i've been using ginac for some months and is very optimum,<br>
> but recently i've been facing a problem with the amount of memory used to store some expressions.<br>
> i have a linear system of ecuations, with the size of around 8000 elements.<br>
><br>
> my first approach on building the matrix was use a map<string, ex*> where each element would correspond to a row element of the matrix.<br>
> and all incognints of that row would be inside the expression ex. for a 4x4 system ecuaiton, the storage would be like this<br>
><br>
> <"certainKey1", ex1* > = B1*symbol2 + A1*symbol1 + D1*symbol4<br>
> <"certainKey2", ex2*> = D2*symbol4 + B2*symbol2 + C2*symbol3<br>
> <"certainKey3", ex3* > = B3*symbol2 + A3*symbol1 + D3*symbol4 + C3*symbol3<br>
> <"certainKey4", ex4*> = A4*symbol1 + B4*symbol2 + C4*symbol3<br>
><br>
> this method was using an acceptable ammount of memory, around 15% of 32GB which was pretty good.<br>
> the bad side of this approach was that when building the Ginac::matrix, i had to sort the elements and search each of them on their corresponding row, additionaly some where hidden because they had coefficient "0", so i had a list of symbols and on each row i searched for them, in a sorted way using the "coeff" method that Ginac provides.<br>
> But i repeat, this was slow.<br>
><br>
> The point is that i decided to search for other solution, aiming on reducing the time needed to build the Ginac::Matrix.<br>
> i came with the idea to use map< string, <string, ex> > mapMatrix, which is actually the matrix but sorted automatically because of the strings which are the incognits keyCode.<br>
> now building the matrix is almost instant, no search needed, and all elements already sorted.<br>
><br>
> however, the program is using all the RAM = 32GB when doing the 8000x8000 problem.<br>
><br>
> i checked and rechecked for any memory leak, but havent found any so far,<br>
><br>
> now the question = why did memory increase so much for just segmenting the expressions into separated smaller ones??<br>
> is they same ammount of terms, just in separated sub-expressions., the ex object is too expensive??<br>
><br>
><br>
><br>
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