From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <798e803ad46d7e986daedaa82d5ec9bf@coraid.com>
From: erik quanstrom <quanstro@coraid.com>
Date: Sat, 31 Mar 2007 21:32:17 -0400
To: 9fans@cse.psu.edu
Subject: Re: [9fans] slow performance
In-Reply-To: <e510e47e0703311625sbc2646ay1aa80271fcd380a6@mail.gmail.com>
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when you compiled this on plan 9, you must have 
either replaced stdlib.h with something else or have used
ape.  i substituted libbio and get almost the same performance
you did on linux.  i used my home cpu server, a amd64 revF 3800+.

	cpu% 8c -FVw t.c
	warning: t.c:64 set and not used: t
	cpu% 8l -o t t.8
	cpu% time t >/tmp/xyzw
	2.08u 0.05s 2.36r 	 t

i think the reason for the difference in performance is that somehow
your translation of print was calling write(2) for each integer printed.

assuming i understand the point of this program -- sorting a bunch of
integers, i rewrote this program using an array and qsort, which should
be more memory efficient and faster.  here's what i get

	cpu% time ./u >/tmp/xyz 
	0.08u 0.01s 0.22r 	 ./u

- erik
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#include <u.h>
#include <libc.h>
#include <bio.h>

enum{
	MAX	= 200000,
};

typedef struct Bst Bst;
struct Bst{
	int 	v;
	Bst	*menor;
	Bst	*maior;
};

Biobuf b;

Bst*
pbst(Bst *t)
{
	if(t->menor != 0)
		t->menor = pbst(t->menor);
	Bprint(&b, "%d - ", t->v);
	if(t->maior != 0)
		t->maior = pbst(t->maior);
	return t;
}

Bst*
bstini(int v)
{
	Bst *t;

	t = malloc(sizeof *t);
	t->v = v;
	t->maior = 0;
	t->menor = 0;
	return t;
}

Bst *
bstadd(int v, Bst *t)
{
	if(t == 0)
		t = bstini(v);
	else if(v >= t->v)
		t->maior = bstadd(v, t->maior);
	else
		t->menor = bstadd(v, t->menor);
	return t;
 }

void
main(void)
{
	Bst *t;
	int i;

	Binit(&b, 1, OWRITE);
	t = 0;
	srand(time(0));
	for(i = 0; i < MAX; i++)
		t = bstadd(rand()%1000, t);
	t = pbst(t);
	exits("");
 }
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#include <u.h>
#include <libc.h>
#include <bio.h>

enum{
	MAX	= 200000,
};

int
intcmp(void *a, void *b)
{
	return *((int*)a)-*((int*)b);
}

void
main(void)
{
	Biobuf b;
	int *t, i;

	Binit(&b, 1, OWRITE);
	
	t = malloc(MAX*sizeof *t);
	srand(time(0));
	for(i = 0; i < MAX; i++)
		t[i] = rand()%1000;
	qsort(t, MAX, sizeof *t, intcmp);
	for(i = 0; i < MAX; i++)
		Bprint(&b, " - %d", t[i]);
	exits("");
 }
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