unofficial mirror of guile-devel@gnu.org 
 help / color / mirror / Atom feed
* string port slow output on big string
@ 2005-02-14  0:22 Kevin Ryde
  2005-02-28  2:48 ` Marius Vollmer
  0 siblings, 1 reply; 5+ messages in thread
From: Kevin Ryde @ 2005-02-14  0:22 UTC (permalink / raw)


[-- Attachment #1: Type: text/plain, Size: 1159 bytes --]

I tried writing a biggish string to a string port, and it was very
slow.  Eg.

    (use-modules (ice-9 time))
    (let ((str (make-string 100000 #\x)))
      (call-with-output-string (lambda (port)
                                 (time (display str port))))
      #f)

gives on my poor 333mhz

    clock utime stime cutime cstime gctime
     7.63  7.58  0.05   0.00   0.00   4.17

I struck this trying to use regexp-substitute/global on a file slurped
into memory.  It was 130k, which is a decent size, but it's well
within the realm of reason.


I think strports.c st_write ends up doing a realloc and copy every 80
bytes of the block it's writing.  It knows the size, but it lets
st_flush just grow by 80 bytes at a time.

The change below speeds it up from 7 seconds to 10 ms for me.

But I don't know if the read side bits of this change are right.  Is
it supposed to update read_pos, read_end and read_buf_size to be the
end of the string, or something?


(Of course what would be even nicer would be to avoid big reallocing
altogether, like keep a list of chunks and only join them when a
get-string call wants the entire block.  But that can wait.)



[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: strports.c.write.diff --]
[-- Type: text/x-patch, Size: 906 bytes --]

--- strports.c.~1.105.~	2005-01-28 08:25:34.000000000 +1100
+++ strports.c	2005-02-14 11:20:05.000000000 +1100
@@ -142,18 +142,14 @@
   scm_t_port *pt = SCM_PTAB_ENTRY (port);
   const char *input = (char *) data;
 
-  while (size > 0)
-    {
-      int space = pt->write_end - pt->write_pos;
-      int write_len = (size > space) ? space : size;
-      
-      memcpy ((char *) pt->write_pos, input, write_len);
-      pt->write_pos += write_len;
-      size -= write_len;
-      input += write_len;
-      if (write_len == space)
-	st_flush (port);
-    }
+  /* if not enough room for "size" then make that amount and an additional
+     SCM_WRITE_BLOCK */
+  if (size > pt->write_end - pt->write_pos)
+    st_resize_port (pt, pt->write_pos - pt->write_buf
+                        + size + SCM_WRITE_BLOCK);
+
+  memcpy ((char *) pt->write_pos, input, size);
+  pt->write_pos += size;
 }
 
 static void

[-- Attachment #3: Type: text/plain, Size: 143 bytes --]

_______________________________________________
Guile-devel mailing list
Guile-devel@gnu.org
http://lists.gnu.org/mailman/listinfo/guile-devel

^ permalink raw reply	[flat|nested] 5+ messages in thread

end of thread, other threads:[~2005-08-10 22:32 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2005-02-14  0:22 string port slow output on big string Kevin Ryde
2005-02-28  2:48 ` Marius Vollmer
     [not found]   ` <87r7ddrzgl.fsf@zip.com.au>
2005-08-02 12:37     ` Alan Grover
2005-08-03 22:43       ` Kevin Ryde
2005-08-10 22:32     ` Marius Vollmer

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).