RISC OS Open: Forum: BASIC VFP speed

Jul 1, 2022 7:26pm

This time last year, this Latest news encouraged use of VFP via BASIC VI VFP. Since then there have been updates to both BASIC and to module VFPSupport, but I am not getting the expected fast SIN and COS from the little demo program shown there.

Setups

 
ARMX6  OS 5.29 (01-Feb-2022)
Pi 400 OS 5.29 (07-Apr-2022)
BASIC    1.84 (23-JUN-2021)−BASIC V
BASIC64  1.84 (23-JUN-2021)—BASIC VI FPA
BASICVFP 1.84 (23-JUN-2021)−BASIC VI VFP
VFPSupport 0.18 (24-Nov-2021)

Results

 
         ARMX6  Pi 400
BASIC       cs      cs
V         1364     395
VI FPA   15335    8848
VI VFP    2455     541

I’m not surprised that FPA is so slow, nor that the Pi is faster than the ARMX6, but why is BASIC VFP slower than BASIC V on both machines?

Jul 1, 2022 11:35pm

David J. Ruck (33) 1635 posts

BASIC’s own fp type has always been very quick compared to IEEE standard implementations, even in hardware.

Jul 2, 2022 5:12am

Clive Semmens (2335) 3276 posts

Which isn’t really surprising, since BASIC V has 5-byte reals, whereas BASIC VI has 8-byte reals.

Jul 2, 2022 1:04pm

Bernard Boase (169) 208 posts

All true, but in Martin Avison’s comment attached to the original news item I referenced, his Test2 showed BASIC VI VFP’s speed as twice that of BASIC V. What might be different in my test?

Jul 2, 2022 1:35pm

David Feugey (2125) 2709 posts

Not all VFP units are equal.
Martin tested this code on a Titanium…

BASIC VFP speed

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Jul 1, 2022 7:26pm Bernard Boase (169) 208 posts	This time last year, this Latest news encouraged use of VFP via BASIC VI VFP. Since then there have been updates to both BASIC and to module VFPSupport, but I am not getting the expected fast SIN and COS from the little demo program shown there. Setups `ARMX6 OS 5.29 (01-Feb-2022) Pi 400 OS 5.29 (07-Apr-2022) BASIC 1.84 (23-JUN-2021)−BASIC V BASIC64 1.84 (23-JUN-2021)—BASIC VI FPA BASICVFP 1.84 (23-JUN-2021)−BASIC VI VFP VFPSupport 0.18 (24-Nov-2021)` Results `ARMX6 Pi 400 BASIC cs cs V 1364 395 VI FPA 15335 8848 VI VFP 2455 541` I’m not surprised that FPA is so slow, nor that the Pi is faster than the ARMX6, but why is BASIC VFP slower than BASIC V on both machines?

Jul 1, 2022 11:35pm David J. Ruck (33) 1635 posts	BASIC’s own fp type has always been very quick compared to IEEE standard implementations, even in hardware.

Jul 2, 2022 5:12am Clive Semmens (2335) 3276 posts	Which isn’t really surprising, since BASIC V has 5-byte reals, whereas BASIC VI has 8-byte reals.

Jul 2, 2022 1:04pm Bernard Boase (169) 208 posts	All true, but in Martin Avison’s comment attached to the original news item I referenced, his Test2 showed BASIC VI VFP’s speed as twice that of BASIC V. What might be different in my test?

Jul 2, 2022 1:35pm David Feugey (2125) 2709 posts	Not all VFP units are equal. Martin tested this code on a Titanium…