 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
VB Forum / General 2 / May 2008Need for Speed
Is there any difference in speed between these 2 methods? In .BAS Module Global Const MPH_TO_FPS = 5280 / 3600 'Convert MPH to Feet per Second In .FRM File ans14 = MPH1 * MPH_TO_FPS 'Vel. (ft/sec) and ans14 = MPH1 * 5280 / 3600 'Vel. (ft/sec) > Is there any difference in speed between these 2 methods? > > In .BAS Module > Global Const MPH_TO_FPS = 5280 / 3600 'Convert MPH to Feet per Second > In .FRM File > ans14 = MPH1 * MPH_TO_FPS 'Vel. (ft/sec) > > and > ans14 = MPH1 * 5280 / 3600 'Vel. (ft/sec) If you only do it once, then it hardly matters. If you do it repeatedly then the first is better because it involves only one FP operation. BUT: if you haven't typed the variables and constants, then you'll get Variants, so wondering about speed is pointless. (-: If you're using Singles, then type everything as such: Global Const MPH_TO_FPS As Single = 5280 / 3600 .. .. Dim ans14 As Single Dim MPH1 As Single ans14 = MPH1 * MPH_TO_FPS -- Jim Mack MicroDexterity Inc www.microdexterity.com > > Is there any difference in speed between these 2 methods? > > [quoted text clipped - 30 lines] > MicroDexterity Inc > www.microdexterity.com Thanks this will be in a loop and these are defined as Dim ans14 As Double Dim MPH1 As Double >> Jim Mack wrote: > [quoted text clipped - 13 lines] > Dim ans14 As Double > Dim MPH1 As Double Then type the constant as Double too. But you will get better speed using all Singles if you don't need the extra precision -- and almost nothing that models the real world (like MPH) requires Doubles. -- Jim Mack MicroDexterity Inc www.microdexterity.com > >> Jim Mack wrote: > > [quoted text clipped - 22 lines] > MicroDexterity Inc > www.microdexterity.com The reason for using double is the customer wants to see 12 decimal places. Thanks Again, Stan >> Then type the constant as Double too. But you will get better speed >> using all Singles if you don't need the extra precision -- and almost >> nothing that models the real world (like MPH) requires Doubles. > > The reason for using double is the customer wants to see 12 decimal > places. Because every 0.00000000528 of a foot per hour helps! ;-) > >> Then type the constant as Double too. But you will get better speed > >> using all Singles if you don't need the extra precision -- and almost [quoted text clipped - 4 lines] > > Because every 0.00000000528 of a foot per hour helps! ;-) No that was just an example. For the CONST use. This is real output where because of the wrist pin offset velocity is not zero at 180 degrees and he wants to know at what degree velocity is zero to 12 decimal. Bore = 4.0 Stroke = 3.25 Rod Length = 5.7 RPM = 6500 Wrist Pin Offset = 0.01 Maximum Piston Velocity 5754.922719 FPM @ 75.078416256241 Degrees Piston Piston Crank Angle Velocity Acceleration Degree FT/Sec FT/Sec/Sec 179.85900000000 0.000456276916 -44854.925521303500 179.85910000000 0.000341264287 -44854.925356947700 179.85920000000 0.000226251658 -44854.925192605500 179.85930000000 0.000111239030 -44854.925028276700 179.85940000000 -0.000003773598 -44854.924863961600 179.85950000000 -0.000118786226 -44854.924699659900 179.85960000000 -0.000233798853 -44854.924535371800 179.85970000000 -0.000348811480 -44854.924371097300 179.85980000000 -0.000463824106 -44854.924206836300 179.85990000000 -0.000578836732 -44854.924042588800 > The reason for using double is the customer > wants to see 12 decimal places. Have you asked him why? Mike Is there any difference in speed between these 2 methods? In .BAS Module Global ans1 As Double Global ans10 As Double Global ans14 As Double Global Const DEG_TO_RAD As Double = kPI / 180# 'Convert Degrees to RAD's --- First Method In .FRM File in a Loop ans14 = ans1 * DEG_TO_RAD --- Second Method In .FRM File ans10 = kPI / 180# In .FRM File in a Loop ans14 = ans1 * ans10 > Is there any difference in speed between these 2 methods? > [quoted text clipped - 15 lines] > In .FRM File in a Loop > ans14 = ans1 * ans10 Any time you can use a constant number, it's *always* faster to just use the constant than to recalculate the number each time. In this particular case, the first method calculates DEG_TO_RAD once, at compile time, while the second method calculates it each time "ans10 = kPI / 180#" is hit. If that line only happens once during the program then the time hit is probably not noticeable (by humans, anyway)... but if you already have DEG_TO_RAD declared anyway, why not just use it?  SignatureWhere did you get this 60Hz ground hum you call brain activity? |
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2010 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.