0006180: llFloor operates on doubles rather than floats, producing differences in expected results - MantisBT

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ID

Project

Category

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Date Submitted

Last Update

0006180

opensim

[REGION] Script Functions

public

2012-08-15 04:08

2012-08-18 04:32

Reporter

SignpostMarv

Assigned To

Priority

normal

Severity

major

Reproducibility

always

Status

patch included

Resolution

open

Platform

Operating System

Operating System Version

Product Version

master (dev code)

Target Version

Fixed in Version

Summary

0006180: llFloor operates on doubles rather than floats, producing differences in expected results

Description

The repro script indicates 27 for all values in Second Life, whereas OpenSim indicates 27 for the value of a and 26 for the llFloor() results.

The attached patch changes the behaviour of llFloor() in OpenSim to match the behaviour of llFloor() in Second Life

Steps To Reproduce

default
{
    touch_start(integer t)
    {
        float a = 26.9999995;
        llSay(0, llList2CSV([
            a,
            llFloor(a),
            llFloor(26.9999995)
        ]));
    }
}

Tags

No tags attached.

Git Revision or version number

dc82ad0

Run Mode

Standalone (1 Region) , Grid (1 Region per Sim)

Physics Engine

BasicPhysics

Script Engine

Environment

.NET / Windows32, .NET / Windows64

Mono Version

None

Viewer

llFloor-precision-problem.patch [^] (1,129 bytes) 2012-08-15 04:08 [Show Content] [Hide Content]

From ab561b1ca976c0193b02439a656290e3d86707b7 Mon Sep 17 00:00:00 2001
From: SignpostMarv <github@signpostmarv.name>
Date: Wed, 15 Aug 2012 12:02:59 +0100
Subject: [PATCH] typecasting the double to a float to mimic the behaviour of
 Second Life when handling values such as 26.9999995 being
 returned as 27 rather than 26 which was the previous
 behaviour

---
 OpenSim/Region/ScriptEngine/Shared/Api/Implementation/LSL_Api.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/OpenSim/Region/ScriptEngine/Shared/Api/Implementation/LSL_Api.cs b/OpenSim/Region/ScriptEngine/Shared/Api/Implementation/LSL_Api.cs
index a06ddd7..397ea77 100644
--- a/OpenSim/Region/ScriptEngine/Shared/Api/Implementation/LSL_Api.cs
+++ b/OpenSim/Region/ScriptEngine/Shared/Api/Implementation/LSL_Api.cs
@@ -398,7 +398,7 @@ namespace OpenSim.Region.ScriptEngine.Shared.Api
         public LSL_Integer llFloor(double f)
         {
             m_host.AddScriptLPS(1);
-            return (int)Math.Floor(f);
+            return (int)Math.Floor((float)f);
         }
 
         public LSL_Integer llCeil(double f)
-- 
1.7.11.msysgit.1

Relationships

Notes
(0022136) justincc (administrator) 2012-08-15 14:26	It seems to me that this points to a more fundamental issue. If llFloor() is cast internally from double to float then llCeil(), llRound(), etc. should be as well. But then one could ask why LSL_Float was modelled internally using a double rather than a float and save all this and future casting.

(0022137) SignpostMarv (reporter) 2012-08-15 14:32	26.9999995 should ceil to 27 is 26.9999995 or float-cast to 27. I can only think llRound would have issues if it was fed a double greater than 0.5 that typecast to float would be less than 0.5

(0022138) justincc (administrator) 2012-08-17 15:55	No, there are other cases. For instance, in SL default { touch_start(integer t) { float a = 27.0000002; llSay(0, llList2CSV([ a, llCeil(a), llCeil(27.0000002) ])); } } Object: 27.000000, 27, 27 but will return Primitive: 27.000000, 28, 28 because SL casts the literals to floats with less precision than doubles. It wouldn't surprise me if there were lots of examples of this though I admit I haven't looked further.

(0022139) justincc (administrator) 2012-08-17 15:56	Which is why I think it would be much better to cast these straight off to floats rather than doubles if one really wants to be LSL compliant. Whether this is a good idea or not is another question.

Issue History
Date Modified	Username	Field	Change
2012-08-18 04:32	DMX04	New Issue
2012-08-18 04:32	DMX04	Issue generated from: 0006160

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