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Shell Programming and Scripting
Matrix to 3 col sorted
Post 303003886 by ctsgnb on Friday 22nd of September 2017 06:08:49 AM
09-22-2017
Whatever strategy you choose, according to your expectation, you will get an output file that is near 5 times bigger than your input file.
input file :
rows = 400k
columns = 3000
Total amount of datas = 400k x 3000 = 1,2 billions
output file :
rows = (400k -1) x ( 3000 -3 )
"-1" because of the header row
"-3" because the 3 first contains the datas you want
columns = 5 (i take into account the datas, not the formatting and "__" stuff)
Total amount of datas = 5 x (400k -1) x ( 3000 -3 ) = 5,99...billions
Indeed, since you will be repeating the datas of the first 3 column for each and every subsequent column. (so (3 + 2 ) x (3000 - 3) ) rather than having it once for all of them ( "+ 2" is because you even want to add the header and the values of the subsequent column).
So just because of your prerequisits and expectations, for sure you will have to write more data, and thus you will need the corresponding number of I/O writing, independently of the strategy you choose.
If you have a huge amount of data to write, then there is and uncompressible amount of time to do it.
Of course I/O operations are quicker to do in RAM or SSD than on a standard hard drive, but still ...
It would be cheaper to save the transposed matrix and request on it
So you will have it twice : in line and in columns ... of course it will cost you 1,2 billions of datas more.
But 1,2 billions x 2 = 2,4 billions is still more than twice smaller than 5,9 billions of datas !
Anyway, processing such an amount of data using files is inappropriate : this is what Database have been designed for...
My 2 cents ...
PS// The reality might even be worse since i didn't even take into account the size of the datas, just the number of them ...
input file :
rows = 400k
columns = 3000
Total amount of datas = 400k x 3000 = 1,2 billions
output file :
rows = (400k -1) x ( 3000 -3 )
"-1" because of the header row
"-3" because the 3 first contains the datas you want
columns = 5 (i take into account the datas, not the formatting and "__" stuff)
Total amount of datas = 5 x (400k -1) x ( 3000 -3 ) = 5,99...billions
Indeed, since you will be repeating the datas of the first 3 column for each and every subsequent column. (so (3 + 2 ) x (3000 - 3) ) rather than having it once for all of them ( "+ 2" is because you even want to add the header and the values of the subsequent column).
So just because of your prerequisits and expectations, for sure you will have to write more data, and thus you will need the corresponding number of I/O writing, independently of the strategy you choose.
If you have a huge amount of data to write, then there is and uncompressible amount of time to do it.
Of course I/O operations are quicker to do in RAM or SSD than on a standard hard drive, but still ...
It would be cheaper to save the transposed matrix and request on it
So you will have it twice : in line and in columns ... of course it will cost you 1,2 billions of datas more.
But 1,2 billions x 2 = 2,4 billions is still more than twice smaller than 5,9 billions of datas !
Anyway, processing such an amount of data using files is inappropriate : this is what Database have been designed for...
My 2 cents ...
PS// The reality might even be worse since i didn't even take into account the size of the datas, just the number of them ...
Last edited by ctsgnb; 09-22-2017 at 12:18 PM..
This User Gave Thanks to ctsgnb For This Post:
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LEARN ABOUT MOJAVE
datas
datas(3U) InterViews Reference Manual datas(3U) NAME
ColorData, GSData, MobilityData, MoveData, VoidData - Data subclasses for storing common undo information SYNOPSIS
#include <Unidraw/Commands/datas.h> DESCRIPTION
The Unidraw library predefines several Data subclasses for storing common undo information: ColorData stores two PSColors (usually repre- senting foreground and background colors), while GSData stores a complete set of graphics state in a FullGraphic object. MobilityData stores the mobility and graphics state information needed to undo a change in mobility. MoveData stores a horizontal and vertical distance. VoidData stores a void pointer as a useful alternative to deriving trivially from Data just to store one word of information. COLORDATA PUBLIC OPERATIONS
ColorData(PSColor*, PSColor*) Create a ColorData instance, supplying the PSColor objects it stores. GSDATA PUBLIC OPERATIONS
GSData(Graphic*) Create a GSData instance, supplying the Graphic object from which to copy a complete set of graphics state. The GSData constructor copies this information into its _gs member, from whence it can be retrieved later. MOBILITYDATA PUBLIC OPERATIONS
MobilityData(Mobility, Graphic*) Create a MobilityData instance, supplying the mobility and a Graphic object from which to copy a complete set of graphics state. The MobilityData constructor copies the graphic into its _gs member, from whence it can be retrieved later. MOVEDATA PUBLIC OPERATIONS
MoveData(float, float) Create a MoveData instance, supplying two floating point numbers that normally represent horizontal and vertical movement. VOIDDATA PUBLIC OPERATIONS
VoidData(void*) Create a VoidData instance, supplying a pointer to an object of unknown type. SEE ALSO
Data(3U), Graphic(3U), globals(3U) Unidraw 24 January 1991 datas(3U)