HP 50g Graphing Fibt Comparing ProgramExecution Time, Techniques used in Fibt, Required Programs

FIBT (Comparing ProgramExecution Time)

FIB1 calculates intermediate values Fi more than once, while FIB2 calculates each intermediate Fi only once. Consequently, FIB2 is faster. The difference in speed increases with the size of n because the time required for FIB1 grows exponentially with n, while the time required for FIB2 grows only linearly with n.

FIBT executes the TICKS command to record the execution time of FIB1 and FIB2 for a given value of n.

Level 1	→	Level 3	Level 2	Level 1
n	→	Fn	FIB1 TIME: z	FIB2 TIME: z

Techniques used in FIBT

Structured programming. FIBT calls both FIB1 and FIB2.

Programmatic use of calculator clock. FIBT executes the TICKS command to record the start and finish of each subprogram.

Labeling output. FIBT tags each execution time with a descriptive message.

Required Programs

FIB1 (page 21) calculates Fn using recursion.

FIB2 (page 22) calculates Fn using looping.

FIBT program listing

		Program:	Comments:
		«
		DUP TICKS SWAP	Copies n, then executes FIB1, recording the
		FIB1 SWAP TICKS SWAP	start and stop time.
		B→R 8192 /	Calculates the elapsed time, converts it to a
			real number, and converts that number to
			seconds.
			Leaves the answer returned by FIB1 in level 2.
		"FIB1 TIME" →TAG	Tags the execution time.
		ROT TICKS SWAP FIB2	Executes FIB2, recording the start and stop
		TICKS	time.
		SWAP DROP SWAP	Drops the answer returned by FIB2 (FIB1
		B→R 8192 /	returned the same answer). Calculates the
			elapsed time for FIB2 and converts to seconds.
		"FIB2 TIME" →TAG	Tags the execution time.
		»
		`OFIBT K	Stores the program in FIBT.
Checksum: # 23164d
Bytes:	129

24 RPL Programming Examples