Low efficiency of the mpf_out_str function !

[Jan Doornaert]

Jason,

Have you tried running the program with output NOT to stdout, but to
file?
I don't think the "conversion" from GMP-internal format to decimal takes
*that* much time, but the actual formatted output on-screen (think
"printf") might slow things down (especially for the number of characters
you're outputting)...

CU, JDO

  From: "賴 秀琴"
  To: gmp-discuss at swox.com
  Subject: Low efficiency of the mpf_out_str function !
  Date: Wed, 7 Nov 2007 21:39:13 +0800 (CST)

  I am a newbie to the GMPand trying to run some example codes ! I find
  the result of gmp-chudnovsky.c running strange on my computer. It
  shows the efficiency of the mpf_out_str function seems to be very
  low. When I try to calculate 800000 digits of pi , the core
  calculation take 13.6 sec , but the digits print-out task take more
  than 56 sec ( use a stop watch) why ?? Jason Lin the following are
  the details------------------- djgpp 2.03
  with gmp 4.1.2 (precompiled package)
  on a Windows XP command console running with Pentium-4 1.6 GHz / 1G
  RAM d:\dp>gcc -Wall -O2 -s -o chud.exe gmp-chudnovsky.c -lm -lgmp
  case1:d:\dp>chud 500000 1           <-  to get 500000 digits#terms=35256,
  depth=17
  sieve   time =  0.000
  ...................................................
  bs      time =  5.110
  gcd  time =  0.330
  div     time =  1.099
  sqrt    time =  0.604
  mul     time =  0.385
  total   time =  7.198
  P size=727581 digits (1.455162)
  Q size=727575 digits (1.455150)
  pi(0,35256)=Totally 29 sec to get the final result
  (22 sec for the mpf_out_str function ) case2:
  d:\dp>chud 800000 1    <- to get 800000 digits
  #terms=56410, depth=17
  sieve   time =  0.000
  ...................................................
  bs      time = 10.000
  gcd  time =  0.495
  div     time =  1.923
  sqrt    time =  0.989
  mul     time =  0.714
  total   time = 13.626
  P size=1164133 digits (1.455166)
  Q size=1164127 digits (1.455159)
  pi(0,56410)=Totally 69 sec to get the final result
  (56 sec for the mpf_out_str function )
  ---------------------------------------------print out code in
  gmp-chudnovsky.c if (out&1)  {
  printf("pi(0,%ld)=\n", terms);
  mpf_out_str(stdout, 10, d+2, qi);    <---- it is the hot spot
  printf("\n");

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