From: jz AT bcsupernet DOT com
Newsgroups: comp.os.msdos.djgpp
Subject: re:printf("%.6f")
Date: 26 Jan 1997 20:42:50 GMT
Organization: Zip News
Lines: 58
Message-ID: <5cgfka$pp0@clark.zippo.com>
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp

>On 25 Jan 1997 20:51:52 GMT, jz AT bcsupernet DOT com wrote:
>
>>Can anyone tell me why my printf("%.6f") is running so incredibly 
slowly?
>>I'm running gcc on a 386 with no copro if that's a clue.  The same 
line 
>>compiled under Borland C is MUCH faster.  this is more than a pmode 
problem 

>Is this the only line in your program?  If so, then the program 
compiled 
>under DJGPP will always run slower.  This is because DJGPP spends a 
lot of 
>time in startup code compared to a single library function like 
printf().

No, it isn't the only line in my program, but it is the offending code 
in 
terms of speed.  I realize it is an incomplete statement.  The speed 
problem 
is converning the %.6f conversion in formatted output.  I know this 
because I 
tried sprintf, printf and fprintf all with the same results.  I also 
removed 
the %.6f conversions and the problem disappeared.  The surrounding code 
is not 
rellevant to the problem.  For example 
	main(){
	  float a,b,c;
	  int l;
	
	  a=3.24;
	  b = 0.00423;
	  c = 3464.99887;
	  for(l=1;l <1000;l++){
 	    printf("%.6f  %.6f  %.6f\n", a,b,c);
	    a+=3.55;
	    b*=1.4;
	    c-= .00024;
	  }
        }

Each iteration of the loop is taking about a half a second.  the entire 
program takes just under 6 minutes to run which is just silly. The same 
program with the %.6f's taken out takes 10 seconds.  With the entire 
printf removed it takes four seconds.  So, obviously the %.6f 
conversion is very very slow.  the question I have is why?  And do I 
have to code my own routine to convert from float to text or does 
anyone know of one I can just go get (I'm lazy) :)   thankyou.


>Look at sprintf().  It does everything printf() does, except the 
output is 
sent
>to a character array (string) which is automatically null-terminated.

fprintf, sprintf and printf all take similar lengths of time on %.6f