Hello. I'm a fairly new user of IDL; so is a user of mine, on whose behalf I
am posting this message. We are using IDL V2.0 on OpenVMS VAX.
The task is to read in a set of numbers from a disk file into a 2-dimensional
array. The disk file has 3 numbers per line, about 4000 lines. I include at
the end of this post the IDL code which does the read. Problem is, the code
never finishes; IDL runs out of memory beforehand. I increased the user's max
memory allotment, and the program went a little further before running out of
memory. Back-of-envelope calculations showed the user needs about 48Kb to hold
this data, of 93 pages (512 bytes/page). IDL itself uses ~6000 pages. I gave
her account an upper limit of 25000 pages; enough room for IDL and a 810666x3
array! What is going on???
I suspect the array concatenation operator is the culprit, but I can't say why.
Here's the relevant code fragment, which is within a loop:
READF, 1, temp
IF first THEN BEGIN
data = temp
first = ''
ENDIF ELSE BEGIN
data = [data,temp]
ENDELSE
Both data and temp have been previously declared FLTARR(1,parameters), where
parameters is 3. The help command, when given after the crash, shows DATA as
being something like (3100,3), and only 2% of the symbol space used.
As I said, this doesn't make sense. My hunch is there's a side effect of array
concatenation that eating up memory, never releasing it. Has anyone has
experience with this type of programming bug and how to fix it?
Larry Bleau
University of Maryland
bleau@umdsp.umd.edu
301-405-6223
Complete IDL code:
; this IDL program is for quick and dirty plotting
; it opens a file, reads a given number of parameters and plots any number
; of parameters versus one parameter
filename = ' '
PRINT, ' Enter name of data file'
READ, filename
PRINT, ' Enter number of parameters to read'
READ, parameters
data = FLTARR(1,parameters)
temp = FLTARR(1,parameters)
OPENR, 1, filename
first = 'first'
ret = ''
WHILE NOT EOF(1) DO BEGIN
;&
temp_ret = size(data)
if temp_ret(1) mod 1000 eq 0 then begin
PRINT, ' ENTER RETURN'
READ, ret
endif
;&
ON_IOERROR, go_on
READF, 1, temp
IF first THEN BEGIN
data = temp
first = ''
ENDIF ELSE BEGIN
data = [data,temp]
ENDELSE
go_on:
ENDWHILE
CLOSE, 1
; get plot information
plot_start:
xlinlog = ' '
ylinlog = ' '
PRINT, ' Plot information'
PRINT, 'Enter log for logarithmic or lin for linear x axis '
READ, xlinlog
PRINT, 'Enter log for logarithmic or lin for linear y axis '
READ, ylinlog
PRINT, ''
PRINT, 'Enter the number of parameters to plot '
READ, plot_param
y_param = INTARR(plot_param)
PRINT, 'Enter parameter number for the x axis '
READ, x_param
x_param = x_param - 1
y_min = 1.e10
y_max = 0.
FOR i = 0, plot_param-1 DO BEGIN
PRINT, 'Enter parameter number to plot '
READ, temp1
y_param(i) = temp1 - 1
y_min = y_min < MIN(data(*,temp1-1))
y_max = y_max > MAX(data(*,temp1-1))
ENDFOR
; create plot
case_start:
CASE 1 OF
xlinlog EQ 'log' AND ylinlog EQ 'log' : BEGIN
PLOT_OO, data(*,x_param), data(*,y_param(0)), $
YRANGE=[y_min, y_max]
END
xlinlog EQ 'log' AND ylinlog EQ 'lin' : BEGIN
PLOT_OI, data(*,x_param), data(*,y_param(0)), $
YRANGE=[y_min, y_max]
END
xlinlog EQ 'lin' AND ylinlog EQ 'log' : BEGIN
PLOT_IO, data(*,x_param), data(*,y_param(0)), $
YRANGE=[y_min, y_max]
END
xlinlog EQ 'lin' AND ylinlog EQ 'lin' : BEGIN
PLOT, data(*,x_param), data(*,y_param(0)), $
YRANGE=[y_min, y_max]
END
ELSE : BEGIN
PRINT, ' Make sure lin and log entries are in lower case'
PRINT, 'Enter log for logarithmic or lin for linear x axis '
READ, xlinlog
PRINT, 'Enter log for logarithmic or lin for linear y axis '
READ, ylinlog
GOTO, case_start
END
ENDCASE
FOR i = 1, plot_param-1 DO OPLOT, data(*,x_param), data(*,y_param(i))
; make another plot?
answer = ' '
PRINT, ' Do you want to make another plot?'
READ, answer
IF answer EQ 'Y' OR answer EQ 'y' THEN GOTO, plot_start
END
Larry Bleau
University of Maryland
bleau@umdsp.umd.edu
301-405-6223
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