pow(x,y) code replacement with qip(x,y) function

[Jerry]

I found this little snipet of code in the latest Dr. Dobbs Magazine to replace the f = pow(x,y) with f = qip(x,y).

It has a limitation that y has to be a positive integer.

It appears to be more accurate that CCS's pow() function. The qip(2.5, 5) function only 5\% rom, pow(2.5, 5) function 17\% rom.

My example below with some results.

[Jerry]

I found that it did not paste all the code.

All I can see that is missing is.

#include <math.h> required for CCS's pow(x,y) function.

This is a keeper.



:=/*
:=I found this little snipet of code in the latest Dr. Dobbs Magazine to replace the f = pow(x,y) with f = qip(x,y).
:=
:=It has a limitation that y has to be a positive integer.
:=
:=It appears to be more accurate that CCS's pow() function. The qip(2.5, 5) function only 5\% rom, pow(2.5, 5) function 17\% rom.
:=
:=My example below with some results.
:=
:=*/
:=
:=// #define PIC_16F87X
:=#define PIC_18FXXX
:=
:=#define 98MHZCLOCK
:=// #define 8MHZCLOCK
:=
:=#case
:=
:=#IFDEF PIC_16F87X
:= #include <16F876.h>
:= #fuses hs, nowdt, noprotect, nolvp, put
:=// #device PIC16F876 *=16 icd=TRUE
:= #device PIC16F876 *=16
:= #device adc=8
:=#ENDIF
:=
:=
:=#IFDEF PIC_18FXXX
:= #include <18F252.h>
:= #include "defs_18f.h"
:= #fuses hs, nowdt, noprotect, nolvp, put, NOOSCSEN
:= #device PIC18F252 *=16
:=// #device PIC18F252 *=16 icd=TRUE
:= #device adc=8
:=
:= #build(reset=0x200)
:= #build(interrupt=0x208)
:= #org 0x0000,0x01ff
:= void bootloader() {
:= #asm
:= nop
:= #endasm
:=} // Reserve space for the bootloader
:=
:=#ENDIF
:=
:=
:=#include <math.h>
:=
:=#ifdef 8MHZCLOCK
:= #use delay(clock=8000000) /////////// Check Crystal Value ////////////
:=#endif
:=
:=#ifdef 98MHZCLOCK
:= #use delay(clock=9830400) /////////// Check Crystal Value ////////////
:=#endif
:=
:=#use rs232(baud=9600,xmit=PIN_C6,rcv=PIN_C7)
:=
:=/* Compute pow(x,n)
:= For positive Int n
:= through repeated squaring */
:=
:=float qip(float x, unsigned int n)
:={
:= float h = 1.0;
:=
:= while(n)
:= {
:= if (n & 1)
:= h *= x;
:=
:= x *= x;
:= n >>= 1;
:= }
:= return h;
:=}
:=
:=
:=main()
:={
:= unsigned int i;
:=
:=// printf("\%9.2f ", pow(2.5,i));
:=
:=
:= for (i = 10; i < 33; i++)
:= {
:= printf("\%9.2f ", qip(2,i));
:= printf("\%9.2f\n", pow(2,i));
:= }
:=
:= printf("\n");
:=
:=
:=
:= printf("x , y qip(x,y) pow(x,y) Calculator\n");
:= for (i = 18; i < 24; i++)
:= {
:= printf("2.5,\%d ", i);
:= printf("\%9.2f ", qip(2.5,i));
:= printf("\%9.2f\n", pow(2.5,i));
:= }
:=
:= printf("\n");
:=
:= printf("x , y qip(x,y) pow(x,y) Calculator\n");
:= for (i = 3; i < 9; i++)
:= {
:=// printf("\%9.2f \%9.2f\n", qip(12.1,i), pow(12.1,i)); // This does not work ???
:=
:= printf("12.1,\%d ", i);
:= printf("\%9.2f ", qip(12.1,i));
:= printf("\%9.2f\n", pow(12.1,i));
:=
:=
:= }
:= printf("\n");
:=
:= printf("x , y qip(x,y) pow(x,y) Calculator\n");
:= for (i = 7; i < 14; i++)
:= {
:= printf("5.75,\%d ", i);
:= printf("\%9.2f ", qip(5.75,i));
:= printf("\%9.2f\n", pow(5.75,i));
:= }
:=
:= printf("\n");
:=
:=
:= while(TRUE)
:= {
:= }
:=}
:=
:=/* RESULTS
:=
:=x , y qip(x,y) pow(x,y) Calculator
:=2.5,18 14551914.85 14551939.88 14551915.23
:=2.5,19 36379784.94 36379801.33 36379788.07
:=2.5,20 90949465.03 90949496.62 90949470.18
:=2.5,21 227373659.61 227373722.19 227373675.4
:=2.5,22 568434113.26 568435010.31 568434188.6
:=2.5,23 1421085424.72 1421087451.27 1421085472.0
:=
:=x , y qip(x,y) pow(x,y) Calculator
:=12.1,3 1771.56 1771.56 1771.561
:=12.1,4 21435.88 21435.89 21435.888
:=12.1,5 259374.24 259374.70 259374.246
:=12.1,6 3138428.30 3138430.01 3138428.377
:=12.1,7 37974984.64 37975004.91 37974983.36
:=12.1,8 459497258.06 459497588.87 459497298.6
:=
:=x , y qip(x,y) pow(x,y) Calculator
:=5.75,7 207814.03 207814.11 207814.0532
:=5.75,8 1194930.68 1194930.68 1194930.806
:=5.75,9 6870851.39 6870858.43 6870852.133
:=5.75,10 39507392.94 39507421.25 39507399.76
:=5.75,11 227167513.96 227167899.90 227167548.6
:=5.75,12 1306213229.89 1306213229.89 1306213405.0
:=5.75,13 7510725915.43 7510743737.22 7510727077.0
:=
:=================================================================
:=CCS PCH C Compiler, Version 3.146, 14129
:=
:=Filename: c:\program files\picc\fp-ttspi\powtest.LST
:=
:= ROM used: 1512 (5\%)
:= Largest free fragment is 30744
:= RAM used: 10 (1\%) at main() level
:= 28 (2\%) worst case
:= Stack: 2 locations
:=
:=only this output printf("\%9.2f ", qip(2.5,i));
:=================================================================
:=
:=****************************************************************
:=CCS PCH C Compiler, Version 3.146, 14129
:=
:=Filename: c:\program files\picc\fp-ttspi\powtest.LST
:=
:= ROM used: 5586 (17\%)
:= Largest free fragment is 26670
:= RAM used: 11 (1\%) at main() level
:= 63 (4\%) worst case
:= Stack: 3 locations
:=
:=only this output printf("\%9.2f ", pow(2.5,i));
:=
:=****************************************************************
:=*/
___________________________
This message was ported from CCS's old forum
Original Post ID: 12513