Difference between revisions of "Calc/Performance/misc"
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Basic problem: the most basic cell consumes about 50bytes all told, more complex cells consume far more memory, there are a number of simple & obvious things to re-factor here. | Basic problem: the most basic cell consumes about 50bytes all told, more complex cells consume far more memory, there are a number of simple & obvious things to re-factor here. | ||
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| + | It's trivial to calculate the average cost - simply create a sheet with several thousand cells in it, and measure the heap allocation change on load - with [[memprof]] or some other tool, then divide by the number of cells. Similarly, wins are easy to measure this way. | ||
=== ScBaseCell === | === ScBaseCell === | ||
Revision as of 21:09, 17 March 2006
Contents
Calc Optimisation Opportunities
There are a lot of opportunities in calc for various reasons. This list needs extending:
Cell size
Basic problem: the most basic cell consumes about 50bytes all told, more complex cells consume far more memory, there are a number of simple & obvious things to re-factor here.
It's trivial to calculate the average cost - simply create a sheet with several thousand cells in it, and measure the heap allocation change on load - with memprof or some other tool, then divide by the number of cells. Similarly, wins are easy to measure this way.
ScBaseCell
sc/inc/cell.hxx:
class ScBaseCell
{
protected:
ScPostIt* pNote;
SvtBroadcaster* pBroadcaster;
USHORT nTextWidth;
BYTE eCellType; // enum CellType - BYTE spart Speicher
BYTE nScriptType;
Every cell carries this overhead; note that a chunk of it is not necessary for many cells:
- ScPostIt pointer - very, very infrequently used - we have almost no post-it note per cell.
- SvtBroadcaster - used by cells that are referenced (by a single cell (ie. non-range) reference) from another cell - again, a sub-set of all cells.
Solutions: a little re-factoring required, but stealing a bit-field from eCellType to denote a 'special' cell:
class ScBaseCell
{
protected:
USHORT nTextWidth;
BYTE eCellType : 7; // enum CellType - BYTE spart Speicher
bool bSpecial : 1; // other information to be looked up elsewhere
BYTE nScriptType;
The 'bSpecial' flag could be used to denote that there is a 'note' for this cell (in a separate hash), or that this cell has a single-cell dependant. So - we can save 2/3rds of the base size with fairly little effort.
ScFormulaCell
Problems here.
In-sheet objects
Horribly slow - some VCL & svx issues here.
Large / complex pivot sheets
Jody has some sample data here - links ? - internal Novell sheet (commonly used) taking ~3 hours to re-compute.
threaded calculation
Ideally to scale to hyper-threaded machines we need to crunch a workbook's dependency graph & then thread the calcuation.
