Floating point to integral type

could anybody please explain how "round toward zero" works?
or any documentation on this.
thanks.

If you want the simple answer, it rounds towards zero - that is for any floating point number, rounding will give the nearest integer value closets to 0. So 234.1 ->234.0, while -234.1 -> -234.0.
This is as opposed towards other conventions such as rounding towatds +/- infinity
If you want to blow your brains out trying to really undewrstand this, try this

Similar Messages

Floating point Number & Packed Number

Hai can anyone tell me what is the difference in using floating point & packed Number .
when it will b used ?

<b>Packed numbers</b> - type P
Type P data allows digits after the decimal point. The number of decimal places is generic, and is determined in the program. The value range of type P data depends on its size and the number of digits after the decimal point. The valid size can be any value from 1 to 16 bytes. Two decimal digits are packed into one byte, while the last byte contains one digit and the sign. Up to 14 digits are allowed after the decimal point. The initial value is zero. When working with type P data, it is a good idea to set the program attribute Fixed point arithmetic.Otherwise, type P numbers are treated as integers.
You can use type P data for such values as distances, weights, amounts of money, and so on.
<b>Floating point numbers</b> - type F
The value range of type F numbers is 1x10*-307 to 1x10*308 for positive and negative numbers, including 0 (zero). The accuracy range is approximately 15 decimals, depending on the floating point arithmetic of the hardware platform. Since type F data is internally converted to a binary system, rounding errors can occur. Although the ABAP processor tries to minimize these effects, you should not use type F data if high accuracy is required. Instead, use type P data.
You use type F fields when you need to cope with very large value ranges and rounding errors are not critical.
Using I and F fields for calculations is quicker than using P fields. Arithmetic operations using I and F fields are very similar to the actual machine code operations, while P fields require more support from the software. Nevertheless, you have to use type P data to meet accuracy or value range requirements.
reward if useful

Pack and Floating Point Data Type in ABAP

Dear All,
I am new to ABAP. Started with data types. Came across pack and floating point.
Please let me know what PACK and Floating Point stands for with few examples and the main difference between them.
Regards
Arun V

Hi,
You'd better ask this question in ABAP forum http://forums.sdn.sap.com/forum.jspa?forumID=50 .
Best Regards,
Ada

Conversion of a floating point type field

Hi,
I'm fetching field ATFLV from table AUSP for a particular value of ATINN.ATFLV is a floating point type field.
Can anyone please guide me as to how to convert this field(ATFLV) from floating point no. to a simple no.?
Helpful answers will be rewarded.
Regards,
Sipra

hi,
Do like this,
float f = 234.33;
int i = (int) f; // i has value 234.
reward points if helpful..

Floating Point type in selection screen

Hi,
I need to use a field ausp-atflv in selection screen. Field atflv of type Floating point. But in selection-screen, Floating point type variables are not allowed.
Any suggestions please.
Thanks
Aravind.R

Yes Arvind,
Replace the type with a TYPE P with DECIMALS addtion variable.
Regards
Abhii

Char is a floating point type!?!

The sample test on http://www.scja.de/scja-mock-exam-section1.html states that char is a floating point type..... is this correct?

No it isn't ! Sorry for the mistake - it's corrected right now.
regards,
Ralf Peter

Profibus data type converting to floating point

Hi,
Is there an efficient way to convert the incoming data to the floating point in the NI cRIO Profibus system?
1) The system is : NI cRIO 9068 Controller with Comsoft profibus slave module. The lavview we are using is 2013.
2) We are using profibus slave example and are able to see a array of unsigned 8 bit data. Please see the Output data shown in the attachement.
3) On the other side of profibus system, thrid party profibus master are converting floating points and tranmit the converted data to NI profibus slave.
Attachments:
Screenshoot.png ‏7 KB

If it's just a matter of converting data types once you have the data in LabVIEW, you can always manually scale and convert the data using the arithmetic functions and the "To Double Precision Float" or "To Single Precision Float" functions. You just have to know what floating point value the unsigned byte integer corresponds to. Is that what you're asking?
If you're asking for a way to this inherently with the Profibus functions, I'm afraid I can't be of much help...
Ryan K.

KF of type Floating Point Values

Hi
i had a KF of type Nubmer and data type FLTP-Floating point.
When i see the data loaded in the cube for that KF..
Sample values are '8,8310000000000000E-01' and '1,1690000000000000E-01'
What is E-01 mean and How can i intrept their actual values...
Thaks

Still confused..
For better understanding...can please convert '8,8310000000000000E-01' and '1,1690000000000000E-01' for a number with 5 Decimal places or update me how to convert
Thanks

Byte Order for Floating Point Types

I need to send an array of floating point values from an x86 C++ application to a Java application. I am using a socket to transfer the data. What, if anything, do I have to do about preserving the correct byte order?

Probably nothing.
If you do end up having a problem, look at the java.nio package. Specfically, java.nio.ByteOrder, and java.nio.Double/FloatBuffer.
To be completely safe, I think I'd probably send an enum in some kind of header that indicates what byte order your C++ is sending and use the *Buffer classes to automatically handle the conversion.

Check Floating Point Number

Hello All,
I am having some trouble checking the value of a field with Key Figure type Number with 8 byte floating point. I want to read that field and populate another field with an X if true. For example if that field is equal to 5,0000000000000000E+07 then i want to mark the other field with an 'X'.
The problem is in my code, how do i read that number in the fltp field, such as the number above. my code reads as follows for the 'X' field.
    if SOURCE_FIELDS-abc123 eq 5000000.
      RESULT = 'X'.
    endif.
Thanks everyone in advance

You don't need to worry about converting the code into standard format or floating, just implement your code as you want and it will automatically take care of the conversion. Basically 5,0000000000000000E+07 = 50,000,000.
thanks.
Wond

How to gather a set of floating point numbers from a web page form?

I am pretty new to Java and I am working on a project to apply Benfords law to find the probability of digits submitted by the user. My first step is to gather set of floating point numbers from a web page. How do I go about doing this? Any suggestion or a proper site where I can learn this stuff will be highly appreciated.

I am using NetBeans IDE 5.5.1 and for this project. I have realized that the first question was not well phrased.
I created a web project with 2 jsp files and a class file in it. When my jsp file runs I ask the user to enter a number for finding the probablility based on Benfords law.
This is what I got so far:
This is input.jsp
<h1></h1>
Please enter a number to be checked
<form action="result.jsp" method="post">
<input type="number" name="number" >
<input type="submit" value="Check number">
</form>
</body>
</html>
This is result.jsp
String number=request.getParameter("number");

Inline functions in C, gcc optimization and floating point arithmetic issues

For several days I really have become a fan of Alchemy. But after intensive testing I have found several issues which I'd like to solve but I can't without any help.
So...I'm porting an old game console emulator written by me in ANSI C. The code is working on both gcc and VisualStudio without any modification or crosscompile macros. The only platform code is the audio and video output which is out of scope, because I have ported audio and video witin AS3.
Here are the issues:
1. Inline functions - Having only a single inline function makes the code working incorrectly (although not crashing) even if any optimization is enabled or not (-O0 or O3). My current workarround is converting the inline functions to macros which achieves the same effect. Any ideas why inline functions break the code?
2. Compiler optimizations - well, my project consists of many C files one of which is called flash.c and it contains the main and exported functions. I build the project as follows:
gcc -c flash.c -O0 -o flash.o     //Please note the -O0 option!!!
gcc -c file1.c -O3 -o file1.o
gcc -c file2.c -O3 -o file2.o
... and so on
gcc *.o -swc -O0 -o emu.swc   //Please note the -O0 option again!!!
mxmlc.exe -library-path+=emu.swc --target-player=10.0.0 Emu.as
or file in $( ls *.o ) //Removes the obj files
    do
        rm $file
    done
If I define any option different from -O0 in gcc -c flash.c -O0 -o flash.o the program stops working correctly exactly as in the inline funtions code (but still does not crash or prints any errors in debug). flash has 4 static functions to be exported to AS3 and the main function. Do you know why?
If I define any option different from -O0 in gcc *.o -swc -O0 -o emu.swc the program stops working correctly exactly as above, but if I specify -O1, -O2 or O3 the SWC file gets smaller up to 2x for O3. Why? Is there a method to optimize all the obj files except flash.o because I suspect a similar issue as when compilling it?
3. Flating point issues - this is the worst one. My code is mainly based on integer arithmetic but on 1-2 places it requires flating point arithmetic. One of them is the conversion of 16-bit 44.1 Khz sound buffer to a float buffer with same sample rate but with samples in the range from -1.0 to 1.0.
My code:
void audio_prepare_as()
    uint32 i;
    for(i=0;i<audioSamples;i+=2)
        audiobuffer[i] = (float)snd.buffer[i]/32768;
        audiobuffer[i+1] = (float)snd.buffer[i+1]/32768;
My audio playback is working perfectly. But not if using the above conversion and I have inspected the float numbers - all incorrect and invalid. I tried other code with simple floats - same story. As if alchemy refuses to work with floats. What is wrong? I have another lace whre I must resize the framebuffer and there I have a float involved - same crap. Please help me?
Found the floating point problem: audiobuffer is written to a ByteArray and then used in AS. But C floats are obviously not the same as those in AS3. Now the floating point is resolved.
The optimization issues remain! I really need to speed up my code.
Thank you in advice!

Dear Bernd,
I am still unable to run the optimizations and turn on the inline functions. None of the inline functions contain any stdli function just pure asignments, reads, simple arithmetic and bitwise operations.
In fact, the file containing the main function and those functions for export in AS3 did have memset and memcpy. I tried your suggestion and put the code above the functions calling memset and memcpy. It did not work soe I put the code in a header which is included topmost in each C file. The only system header I use is malloc.h and it is included topmost. In other C file I use pow, sin and log10 from math.h but I removed it and made the same thing:
//shared.h
#ifndef _SHARED_H_
#define _SHARED_H_
#include <malloc.h>
static void * custom_memmove( void * destination, const void * source, unsigned int num ) {
void *result;
__asm__("%0 memmove(%1, %2, %3)\n" : "=r"(result) : "r"(destination), "r"(source), "r"(num));
return result;
static void * custom_memcpy ( void * destination, const void * source, unsigned int num ) {
void *result;
__asm__("%0 memcpy(%1, %2, %3)\n" : "=r"(result) : "r"(destination), "r"(source), "r"(num));
return result;
static void * custom_memset ( void * ptr, int value, unsigned int num ) {
void *result;
__asm__("%0 memset(%1, %2, %3)\n" : "=r"(result) : "r"(ptr), "r"(value), "r"(num));
return result;
static float custom_pow(float x, int y) {
    float result;
__asm__("%0 pow(%1, %2)\n" : "=r"(result) : "r"(x), "r"(y));
return result;
static double custom_sin(double x) {
    double result;
__asm__("%0 sin(%1)\n" : "=r"(result) : "r"(x));
return result;
static double custom_log10(double x) {
    double result;
__asm__("%0 log10(%1)\n" : "=r"(result) : "r"(x));
return result;
#define memmove custom_memmove
#define memcpy custom_memcpy
#define memset custom_memset
#define pow custom_pow
#define sin custom_sin
#define log10 custom_log10
#include "types.h"
#include "macros.h"
#include "m68k.h"
#include "z80.h"
#include "genesis.h"
#include "vdp.h"
#include "render.h"
#include "mem68k.h"
#include "memz80.h"
#include "membnk.h"
#include "memvdp.h"
#include "system.h"
#include "loadrom.h"
#include "input.h"
#include "io.h"
#include "sound.h"
#include "fm.h"
#include "sn76496.h"
#endif /* _SHARED_H_ */
It still behave the same way as if nothing was changed (works incorrectly - displays jerk which does not move, whereby the image is supposed to move)
As I am porting an emulator (Sega Mega Drive) I use manu arrays of function pointers for implementing the opcodes of the CPU's. Could this be an issue?
I did a workaround for the floating point problem but processing is very slow so I hear only bzzt bzzt but this is for now out of scope. The emulator compiled with gcc runs at 300 fps on a 1.3 GHz machine, whereby my non optimized AVM2 code compiled by alchemy produces 14 fps. The pure rendering is super fast and the problem lies in the computational power of AVM. The frame buffer and the enulation are generated in the C code and only the pixels are copied to AS3, where they are plotted in a BitmapData. On 2.0 GHz Dual core I achieved only 21 fps. Goal is 60 fps to have smooth audio and video. But this is offtopic. After all everything works (slow) without optimization, and I would somehow turn it on. Suggestions?
Here is the file with the main function:
#include "shared.h"
#include "AS3.h"
#define FRAMEBUFFER_LENGTH    (320*240*4)
static uint8* framebuffer;
static uint32 audioSamples;
AS3_Val sega_rom(void* self, AS3_Val args)
    int size, offset, i;
    uint8 hardware;
    uint8 country;
    uint8 header[0x200];
    uint8 *ptr;
    AS3_Val length;
    AS3_Val ba;
    AS3_ArrayValue(args, "AS3ValType", &ba);
    country = 0;
    offset = 0;
    length = AS3_GetS(ba, "length");
    size = AS3_IntValue(length);
    ptr = (uint8*)malloc(size);
    AS3_SetS(ba, "position", AS3_Int(0));
    AS3_ByteArray_readBytes(ptr, ba, size);
    //FILE* f = fopen("boris_dump.bin", "wb");
    //fwrite(ptr, size, 1, f);
    //fclose(f);
    if((size / 512) & 1)
        size -= 512;
        offset += 512;
        memcpy(header, ptr, 512);
        for(i = 0; i < (size / 0x4000); i += 1)
            deinterleave_block(ptr + offset + (i * 0x4000));
    memset(cart_rom, 0, 0x400000);
    if(size > 0x400000) size = 0x400000;
    memcpy(cart_rom, ptr + offset, size);
    /* Free allocated file data */
    free(ptr);
    hardware = 0;
    for (i = 0x1f0; i < 0x1ff; i++)
        switch (cart_rom[i]) {
     case 'U':
         hardware |= 4;
         break;
     case 'J':
         hardware |= 1;
         break;
     case 'E':
         hardware |= 8;
         break;
    if (cart_rom[0x1f0] >= '1' && cart_rom[0x1f0] <= '9') {
        hardware = cart_rom[0x1f0] - '0';
    } else if (cart_rom[0x1f0] >= 'A' && cart_rom[0x1f0] <= 'F') {
        hardware = cart_rom[0x1f0] - 'A' + 10;
    if (country) hardware=country; //simple autodetect override
    //From PicoDrive
    if (hardware&8)
        hw=0xc0; vdp_pal=1;
    } // Europe
    else if (hardware&4)
        hw=0x80; vdp_pal=0;
    } // USA
    else if (hardware&2)
        hw=0x40; vdp_pal=1;
    } // Japan PAL
    else if (hardware&1)
        hw=0x00; vdp_pal=0;
    } // Japan NTSC
    else
        hw=0x80; // USA
    if (vdp_pal) {
        vdp_rate = 50;
        lines_per_frame = 312;
    } else {
        vdp_rate = 60;
        lines_per_frame = 262;
    /*SRAM*/
    if(cart_rom[0x1b1] == 'A' && cart_rom[0x1b0] == 'R')
        save_start = cart_rom[0x1b4] << 24 | cart_rom[0x1b5] << 16 |
            cart_rom[0x1b6] << 8 | cart_rom[0x1b7] << 0;
        save_len = cart_rom[0x1b8] << 24 | cart_rom[0x1b9] << 16 |
            cart_rom[0x1ba] << 8 | cart_rom[0x1bb] << 0;
        // Make sure start is even, end is odd, for alignment
        // A ROM that I came across had the start and end bytes of
        // the save ram the same and wouldn't work. Fix this as seen
        // fit, I know it could probably use some work. [PKH]
        if(save_start != save_len)
            if(save_start & 1) --save_start;
            if(!(save_len & 1)) ++save_len;
            save_len -= (save_start - 1);
            saveram = (unsigned char*)malloc(save_len);
            // If save RAM does not overlap main ROM, set it active by default since
            // a few games can't manage to properly switch it on/off.
            if(save_start >= (unsigned)size)
                save_active = 1;
        else
            save_start = save_len = 0;
            saveram = NULL;
    else
        save_start = save_len = 0;
        saveram = NULL;
    return AS3_Int(0);
AS3_Val sega_init(void* self, AS3_Val args)
    system_init();
    audioSamples = (44100 / vdp_rate)*2;
    framebuffer = (uint8*)malloc(FRAMEBUFFER_LENGTH);
    return AS3_Int(vdp_rate);
AS3_Val sega_reset(void* self, AS3_Val args)
    system_reset();
    return AS3_Int(0);
AS3_Val sega_frame(void* self, AS3_Val args)
    uint32 width;
    uint32 height;
    uint32 x, y;
    uint32 di, si, r;
    uint16 p;
    AS3_Val fb_ba;
    AS3_ArrayValue(args, "AS3ValType", &fb_ba);
    system_frame(0);
    AS3_SetS(fb_ba, "position", AS3_Int(0));
    width = (reg[12] & 1) ? 320 : 256;
    height = (reg[1] & 8) ? 240 : 224;
    for(y=0;y<240;y++)
        for(x=0;x<320;x++)
            di = 1280*y + x<<2;
            si = (y << 10) + ((x + bitmap.viewport.x) << 1);
            p = *((uint16*)(bitmap.data + si));
            framebuffer[di + 3] = (uint8)((p & 0x1f) << 3);
            framebuffer[di + 2] = (uint8)(((p >> 5) & 0x1f) << 3);
            framebuffer[di + 1] = (uint8)(((p >> 10) & 0x1f) << 3);
    AS3_ByteArray_writeBytes(fb_ba, framebuffer, FRAMEBUFFER_LENGTH);
    AS3_SetS(fb_ba, "position", AS3_Int(0));
    r = (width << 16) | height;
    return AS3_Int(r);
AS3_Val sega_audio(void* self, AS3_Val args)
    AS3_Val ab_ba;
    AS3_ArrayValue(args, "AS3ValType", &ab_ba);
    AS3_SetS(ab_ba, "position", AS3_Int(0));
    AS3_ByteArray_writeBytes(ab_ba, snd.buffer, audioSamples*sizeof(int16));
    AS3_SetS(ab_ba, "position", AS3_Int(0));
    return AS3_Int(0);
int main()
    AS3_Val romMethod = AS3_Function(NULL, sega_rom);
    AS3_Val initMethod = AS3_Function(NULL, sega_init);
    AS3_Val resetMethod = AS3_Function(NULL, sega_reset);
    AS3_Val frameMethod = AS3_Function(NULL, sega_frame);
    AS3_Val audioMethod = AS3_Function(NULL, sega_audio);
    // construct an object that holds references to the functions
    AS3_Val result = AS3_Object("sega_rom: AS3ValType, sega_init: AS3ValType, sega_reset: AS3ValType, sega_frame: AS3ValType, sega_audio: AS3ValType",
        romMethod, initMethod, resetMethod, frameMethod, audioMethod);
    // Release
    AS3_Release(romMethod);
    AS3_Release(initMethod);
    AS3_Release(resetMethod);
    AS3_Release(frameMethod);
    AS3_Release(audioMethod);
    // notify that we initialized -- THIS DOES NOT RETURN!
    AS3_LibInit(result);
    // should never get here!
    return 0;

128-bit floating point numbers on new AMD quad-core Barcelona?

There's quite a lot of buzz over at Slashdot about the new AMD quad core chips, announced yesterday:
http://hardware.slashdot.org/article.pl?sid=07/02/10/0554208
Much of the excitement is over the "new vector math unit referred to as SSE128", which is integrated into each [?!?] core; Tom Yager, of Infoworld, talks about it here:
Quad-core Opteron? Nope. Barcelona is the completely redesigned x86, and it’s brilliant
Now here's my question - does anyone know what the inputs and the outputs of this coprocessor look like? Can it perform arithmetic [or, God forbid, trigonometric] operations [in hardware] on 128-bit quad precision floats? And, if so, will LabVIEW be adding support for it? [Compare here versus here.]
I found a little bit of marketing-speak blather at AMD about "SSE 128" in this old PDF Powerpoint-ish presentation, from June of 2006:
http://www.amd.com/us-en/assets/content_type/DownloadableAssets/PhilHesterAMDAnalystDayV2.pdf
WARNING: PDF DOCUMENT
Page 13: "Dual 128-bit SSE dataflow, Dual 128-bit loads per cycle"
Page 14: "128-bit SSE and 128-bit Loads, 128b FADD, 128 bit FMUL, 128b SSE, 128b SSE"
etc etc etc
While it's largely just gibberish to me, "FADD" looks like what might be a "floating point adder", and "FMUL" could be a "floating point multiplier", and God forbid that the two "SSE" units might be capable of computing some 128-bit cosines. But I don't know whether that old paper is even applicable to the chip that was released yesterday, and I'm just guessing as to what these things might mean anyway.
Other than that, though, AMD's main website is strangely quiet about the Barcelona announcement. [Memo to AMD marketing - if you've just released the greatest thing since sliced bread, then you need to publicize the fact that you've just released the greatest thing since sliced bread...]

I posted a query over at the AMD forums, and here's what I was told.
I had hoped that e.g. "128b FADD" would be able to do something like the following:
/* "quad" is a hypothetical 128-bit quad precision */
/* floating point number, similar to "long double" */
/* in recent versions of C++:                       */
quad x, y, z;
x = 1.000000000000000000000000000001;
y = 1.000000000000000000000000000001;
/* the hope was that "128b FADD" could perform the */
/* following 128-bit addition in hardware:          */
z = x + y;
However, the answer I'm getting is that "128b FADD" is just a set of two 64-bit adders running in parallel, which are capable of adding two vectors of 64-bit doubles more or less simultaneously:
double x[2], y[2], z[2];
x[0] = 1.000000000000000000000000000001;
y[0] = 1.000000000000000000000000000001;
x[1] = 2.000000000000000000000000000222;
y[1] = 2.000000000000000000000000000222;
/* Apparently the coordinates of the two "vectors" x & y       */
/* can be sent to "128b FADD" in parallel, and the following   */
/* two summations can be computed more or less simultaneously: */
z[0] = x[0] + y[0];
z[1] = x[1] + y[1];
Thus e.g. "128b FADD", working in concert with "128b FMUL", will be able to [more or less] halve the amount of time it takes to compute a dot product of vectors whose coordinates are 64-bit doubles.
So this "128-bit" circuitry is great if you're doing lots of linear algebra with 64-bit doubles, but it doesn't appear to offer anything in the way of greater precision for people who are interested in precision-sensitive calculations.
By the way, if you're at all interested in questions of precision sensitivity & round-off error, I'd highly recommend Prof Kahan's page at Cal-Berzerkeley:
http://www.cs.berkeley.edu/~wkahan/
PDF DOCUMENT: How JAVA's Floating-Point Hurts Everyone Everywhere
http://www.cs.berkeley.edu/~wkahan/JAVAhurt.pdf
PDF DOCUMENT: Matlab's Loss is Nobody's Gain
http://www.cs.berkeley.edu/~wkahan/MxMulEps.pdf

Floating-point numbers: min value

Hi,
the number wrapper classes each define a MAX_VALUE and a MIN_VALUE constant. While the MIN_VALUE of non-floating point numbers are negative numbers, the MIN_VALUE of the floating point numbers are the smallest postive numbers.
From the Javadoc:
Float:
MAX_VALUE:
A constant holding the largest positive finite value of type float, (2-2-23)�2127. It is equal to the hexadecimal floating-point literal 0x1.fffffeP+127f and also equal to Float.intBitsToFloat(0x7f7fffff).
MIN_VALUE:
A constant holding the smallest positive nonzero value of type float, 2-149. It is equal to the hexadecimal floating-point literal 0x0.000002P-126f and also equal to Float.intBitsToFloat(0x1).
MAX_VALUE:
A constant holding the largest positive finite value of type double, (2-2-52)�21023. It is equal to the hexadecimal floating-point literal 0x1.fffffffffffffP+1023 and also equal to Double.longBitsToDouble(0x7fefffffffffffffL).
MIN_VALUE:
A constant holding the smallest positive nonzero value of type double, 2-1074. It is equal to the hexadecimal floating-point literal 0x0.0000000000001P-1022 and also equal to Double.longBitsToDouble(0x1L).
Can someone tell me the MAX_NEGATIVE_VALUE (the finite negative value with the largest absolute value) and the MIN_NEGATIVE_VALUE (the negative value with the smallest nonzero absolute value) of float and double (using the xxxBitsToXxx-methods)?
Thanks!
-Puce

The IEEE754 format is symmetric with respect to the sign, so -MAX_VALUE
and -MIN_VALUE are the values you're looking for.
kind regards,
Jos

Designing for floating point error

Hello,
I am stuck with floating point errors and I'm not sure what to do. Specifically, to determine if a point is inside of a triangle, or if it is on the exact edge of the triangle. I use three cross products with the edge as one vector and the other vector is from the edge start to the query point.
The theory says that if the cross product is 0 then the point is directly on the line. If the cross product is <0, then the point is inside the triangle. If >0, then the point is outside the triangle.
To account for the floating point error I was running into, I changed it from =0 to abs(cross_product)<1e-6.
The trouble is, I run into cases where the algorithm is wrong and fails because there is a point which is classified as being on the edge of the triangle which isn't.
I'm not really sure how to handle this.
Thanks,
Eric

So, I changed epsilon from 1e-6 to 1e-10 and it seems to work better (I am using doubles btw). However, that doesn't really solve the problem, it just buries it deeper. I'm interested in how actual commercial applications (such as video games or robots) deal with this issue. Obviously you don't see them giving you an error every time a floating point error messes something up. I think the issue here is that I am using data gathered from physical sensors, meaning the inputs can be arbitrarily close to each other. I am worried though that if I round the inputs, that I will get different data points with the exact same x and y value, and I'm not sure how the geometry algorithms will handle that. Also, I am creating a global navigation mesh of triangles with this data. Floating point errors that are not accounted for correctly lead to triangles inside one another (as opposed to adjacent to each other), which damages the integrity of the entire mesh, as its hard to get your program to fix its own mistake.
FYI:
I am running java 1.6.0_20 in Eclipse Helios with Ubuntu 10.04x64
Here is some code that didn't work using 1e-6 for delta. The test point new Point(-294.18294451166435,-25.496614108304477), is outside the triangle, but because of the delta choice it is seen as on the edge:
class Point
     double x,y;
class Edge
     Point start, end;
class Triangle
     Edge[] edges;
     public Point[] getOrderedPoints() throws Exception{
          Point[] points = new Point[3];
          points[0]=edges[0].getStart();
          points[1]=edges[0].getEnd();
          if (edges[1].getStart().equals(points[0]) || edges[1].getStart().equals(points[1]))
               points[2]=edges[1].getEnd();
          else if (edges[1].getEnd().equals(points[0]) || edges[1].getEnd().equals(points[1]))
               points[2]=edges[1].getStart();
          else
               throw new Exception("MalformedTriangleException\n"+this.print());
          orderNodes(points);
          return points;
        /** Orders node1 node2 and node3 in clockwise order, more specifically
      * node1 is swapped with node2 if doing so will order the nodes clockwise
      * with respect to the other nodes.
      * Does not modify node1, node2, or node3; Modifies only the nodes reference
      * Note: "order" of nodes 1, 2, and 3 is clockwise when the path from point
      * 1 to 2 to 3 back to 1 travels clockwise on the circumcircle of points 1,
      * 2, and 3.
     private void orderNodes(Point[] points){
          //the K component (z axis) of the cross product a x b
          double xProductK = crossProduct(points[0],points[0], points[1], points[2]);
          /*        (3)
           *          +
           *        ^
           *      B
           * (1)+             + (2)
           *       ------A-->
           * Graphical representation of vector A and B. 1, 2, and 3 are not in
           * clockwise order, and the x product of A and B is positive.
          if(xProductK > 0)
               //the cross product is positive so B is oriented as such with
               //respect to A and 1, 2, 3 are not clockwise in order.
               //swapping any 2 points in a triangle changes its "clockwise order"
               Point temp = points[0];
               points[0] = points[1];
               points[1] = temp;
class TriangleTest
     private double delta = 1e-6;
     public static void main(String[] args) {
                Point a = new Point(-294.183483785282, -25.498196740397056);
          Point b = new Point(-294.18345625812026, -25.49859505161433);
          Point c = new Point(-303.88217906116796, -63.04183512930035);
          Edge aa = new Edge (a, b);
          Edge bb = new Edge (c, a);
          Edge cc = new Edge (b, c);
          Triangle aaa = new Triangle(aa, bb, cc);
          Point point = new Point(-294.18294451166435,-25.496614108304477);
          System.out.println(aaa.enclosesPointDetailed(point));
      * Check if a point is inside this triangle
      * @param point The test point
      * @return     1 if the point is inside the triangle, 0 if the point is on a triangle, -1 if the point is not is the triangle
      * @throws MalformedTriangleException
     public int enclosesPointDetailed(LocalPose point, boolean verbose) throws Exception
          Point[] points = getOrderedPoints();
          int cp1 = crossProduct(points[0], points[0], points[1], point);
          int cp2 = crossProduct(points[1], points[1], points[2], point);
          int cp3 = crossProduct(points[2], points[2], points[0], point);
          if (cp1 < 0 && cp2 <0 && cp3 <0)
               return 1;
          else if (cp1 <=0 && cp2 <=0 && cp3 <=0)
               return 0;
          else
               return -1;
         public static int crossProduct(Point start1, Point start2, Point end1, POint end2){
          double crossProduct = (end1.getX()-start1.getX())*(end2.getY()-start2.getY())-(end1.getY()-start1.getY())*(end2.getX()-start2.getX());
          if (crossProduct>floatingPointDelta){
               return 1;
          else if (Math.abs(crossProduct)<floatingPointDelta){
               return 0;
          else{
               return -1;
}

Floating point to integral type

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