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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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psc
PSC(1) General Commands Manual PSC(1) NAME
psc - prepare sc files SYNOPSIS
psc [-fLkrSPv] [-s cell] [-R n] [-C n] [-n n] [-d c] DESCRIPTION
Psc is used to prepare data for input to the spreadsheet calculator sc(1). It accepts normal ascii data on standard input. Standard out- put is a sc file. With no options, psc starts the spreadsheet in cell A0. Strings are right justified. All data on a line is entered on the same row; new input lines cause the output row number to increment by one. The default delimiters are tab and space. The column for- mats are set to one larger than the number of columns required to hold the largest value in the column. OPTIONS
-f Omit column width calculations. This option is for preparing data to be merged with an existing spreadsheet. If the option is not specified, the column widths calculated for the data read by psc will override those already set in the existing spreadsheet. -L Left justify strings. -k Keep all delimiters. This option causes the output cell to change on each new delimiter encountered in the input stream. The default action is to condense multiple delimiters to one, so that the cell only changes once per input data item. -r Output the data by row first then column. For input consisting of a single column, this option will result in output of one row with multiple columns instead of a single column spreadsheet. -s cell Start the top left corner of the spreadsheet in cell. For example, -s B33 will arrange the output data so that the spreadsheet starts in column B, row 33. -R n Increment by n on each new output row. -C n Increment by n on each new output column. -n n Output n rows before advancing to the next column. This option is used when the input is arranged in a single column and the spreadsheet is to have multiple columns, each of which is to be length n. -d c Use the single character c as the delimiter between input fields. -P Plain numbers only. A field is a number only when there is no imbedded [-+eE]. -S All numbers are strings. -v Print the version of psc SEE ALSO
sc(1) AUTHOR
Robert Bond PSC 7.16 19 September 2002 PSC(1)