Factorio Forums

Zeblote wrote:Maybe the smoke sprites themselves are just white and it's possible to re-color them for different things? That'd be fantastic.

bobucles wrote:Bah, floats are way overused. Pretty much every relevant number can be best represented with an integer or decimal shifted integer. No rounding errors, no magic glitches, no weirdness at extreme ranges. Just good solid numbers from start to finish. Managing inventory values? Use an integer. Dealing with damage values? Decimal shifted integer. Time values? You bet integers are involved. Want to map out every single millimeter from the core of the sun all the way out to pluto? Yeah. That's a 64 bit integer.

The only reason to use floats is if you have a fetish for debugging that NEW STRANGE thing it's screwing up now. Also there's that whole thing about maximizing CPU registers at the ultra high end, because for some circular reason CPUs keep getting loaded with FPUs because people keep overusing floats.

ssilk wrote: ....
Mine is, that floats are really practical, if you want to measure something and keep the relative precision small.
....
Integers can be used to COUNT stuff, not to measure.

ske wrote:Guess what optimizing compilers do? The may change the order of operations if you don't explicitly forbid that.

5.1.2.3 Program execution

[#1] The semantic descriptions in this International Standard describe the behavior of an abstract machine in which issues of optimization are irrelevant.

[#3] In the abstract machine, all expressions are evaluated as specified by the semantics.

[#13] EXAMPLE 5 Rearrangement for floating-point expressions is often restricted because of limitations in precision as well as range. The implementation cannot generally apply the mathematical associative rules for addition or multiplication, nor the distributive rule, because of roundoff error, even in the absence of overflow and underflow.

The implementation cannot generally apply the mathematical associative rules for addition

a+b+c

6.5 Expressions

943 The grouping of operators and operands is indicated by the syntax.72)

951 72) The syntax specifies the precedence of operators in the evaluation of an expression, which is the same as the order of the major subclauses of this subclause, highest precedence first.

952 Thus, for example, the expressions allowed as the operands of the binary + operator (6.5.6) are those expressions defined in 6.5.1 through 6.5.6.

954 Within each major subclause, the operators have the same precedence.

955 Left- or right-associativity is indicated in each subclause by the syntax for the expressions discussed therein.

6.5.5 Multiplicative operators

1143
multiplicative-expression:
cast-expression
multiplicative-expression * cast-expression
multiplicative-expression / cast-expression
multiplicative-expression % cast-expression

sillyfly wrote:

The implementation cannot generally apply the mathematical associative rules for addition

Interesting. That would mean that technically, in C++ an expression like:

Code: Select all

a+b+c

(where a,b,c are floats or doubles) is undefined*, and therefore should result in a compilation error, but as far as I know this it never the case.


*Explanation: Strictly speaking, expressions like a+b+c have no meaning, because + is a binary operation, acting on two, and only two terms at a time. The rule of associativity tells us that (a+b)+c = a+(b+c) (This is well defined because each + only acts on two terms), and so a+b+c can be safely assumed to be any of those two options.


Edit: If I understand correctly, either the designers of C++ or the implementers of C++ compilers chose to simply leave this as something the programmer has to keep in mind and deal with. *sigh*.

DOSorDIE wrote:...and of course with a option to deactivate.

Jaridan wrote:One thing that came to mind after seeing the "Blueprint Book" was, if you could implement a "Repair Bag" or something alike, where all items go to that you pick up and are damaged, since those cannot (atm) be stacked in an inventory and it is a bit frustrating that "damaged" entities can easily take up a lot of space in your inventory.

ratchetfreak wrote: It's very well defined in the operator priority rules actually (left to right).

Any optimization that would use floating point associativity is typically opt-in with a -fastmath flag to the compiler.

manual page of gcc wrote:

Code: Select all

-ffloat-store
    Do not store floating point variables in registers, and inhibit other options that might change whether a floating point value is taken from a register or memory.

    This option prevents undesirable excess precision on machines such as the 68000 where the floating registers (of the 68881) keep more precision than a double is supposed to have. Similarly for the x86 architecture. For most programs, the excess precision does only good, but a few programs rely on the precise definition of IEEE floating point. Use -ffloat-store for such programs, after modifying them to store all pertinent intermediate computations into variables.