Page 180 - ARM 64 Bit Assembly Language

Abstract data types 167

Listing 6.9 Revised makefile for the wordfreq program.

1 C_OBJS=wordfreq.o list.o
2 ASM_OBJS=wl_print_numerical.o
3 OBJS=$(C_OBJS) $(ASM_OBJS)
4
5 CC=aarch64-linux-gnu-gcc
6 LFLAGS=-O2 -g
7 CFLAGS=-I. -O2 -g -Wall
8 SFLAGS=-I. -O2 -g -Wall
9 DEPENDFLAGS=-I. -M
10
11 wordfreq: $(OBJS)
12 $(CC) $(LFLAGS) -o wordfreq $(OBJS)
13
14 .S.o:
15 $(CC) $(SFLAGS) -c $<
16
17 .c.o:
18 $(CC) $(CFLAGS) -c $<
19
20 clean:
21 rm -f *.o *~ wordfreq
22
23 # make depend will create a file ".depend" with all the dependencies
24 depend:
25 rm -f .depend
26 $(CC) $(DEPENDFLAGS) $(C_OBJS:.o=.c) > .depend
27
28 # if we have a .depend file, include it
29 ifeq (.depend,$(wildcard .depend))
30 include .depend
31 endif

6.2.2 Better performance

The word frequency counter, as previously implemented, takes several minutes to count
the frequency of words in this textbook on a Raspberry Pi. Most of the time is spent build-
ing the list of words, and re-sorting the list in order of word frequency. Most of the time for
both of these operations is spent in searching for the word in the list before incrementing its
count or inserting it in the list. There are much more efficient ways to build ordered lists of
data.

Since the code is well modularized using an ADT, the internal mechanism of the list can be
modified without affecting the main program. A major improvement can be made by changing
the data structure from a linked list to a binary tree. Fig. 6.1 shows an example binary tree