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• How do I have an arrow follow different height parabolas depending on how long the player holds down a key?

  - by Moondustt

  i'm trying to throw an arrow in my game, but i'm having a hard time trying to realize how to make a good parabola. What I need: The more you hold "enter" stronger the arrow goes. The arrow angle will be always the same, 45 degrees. This is what I have already have: private float velocityHeld = 1f; protected override void Update(GameTime gameTime) { private void GetKeyboardEvent() { if (Keyboard.GetState().IsKeyDown(Keys.Enter) && !released) { timeHeld += velocityHeld; holding = true; } else { if (holding) { released = true; holding = false; lastTimeHeld = timeHeld; } } } if (released && timeHeld > 0) { float alpha = MathHelper.ToRadians(45f); double vy = timeHeld * Math.Sin(alpha); double vx = timeHeld * Math.Cos(alpha); ShadowPosition.Y -= (int)vy; ShadowPosition.X += (int)vx; timeHeld -= velocityHeld; } else { released = false; } } My question is, what do I need to do to make the arrow to go bottom as it loses velocity (timeHeld) to make a perfect parabola?

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• value types in the vm

  - by john.rose

  value types in the vm p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px Times} p.p2 {margin: 0.0px 0.0px 14.0px 0.0px; font: 14.0px Times} p.p3 {margin: 0.0px 0.0px 12.0px 0.0px; font: 14.0px Times} p.p4 {margin: 0.0px 0.0px 15.0px 0.0px; font: 14.0px Times} p.p5 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px Courier} p.p6 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px Courier; min-height: 17.0px} p.p7 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px Times; min-height: 18.0px} p.p8 {margin: 0.0px 0.0px 0.0px 36.0px; text-indent: -36.0px; font: 14.0px Times; min-height: 18.0px} p.p9 {margin: 0.0px 0.0px 12.0px 0.0px; font: 14.0px Times; min-height: 18.0px} p.p10 {margin: 0.0px 0.0px 12.0px 0.0px; font: 14.0px Times; color: #000000} li.li1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px Times} li.li7 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px Times; min-height: 18.0px} span.s1 {font: 14.0px Courier} span.s2 {color: #000000} span.s3 {font: 14.0px Courier; color: #000000} ol.ol1 {list-style-type: decimal} Or, enduring values for a changing world. Introduction A value type is a data type which, generally speaking, is designed for being passed by value in and out of methods, and stored by value in data structures. The only value types which the Java language directly supports are the eight primitive types. Java indirectly and approximately supports value types, if they are implemented in terms of classes. For example, both Integer and String may be viewed as value types, especially if their usage is restricted to avoid operations appropriate to Object. In this note, we propose a definition of value types in terms of a design pattern for Java classes, accompanied by a set of usage restrictions. We also sketch the relation of such value types to tuple types (which are a JVM-level notion), and point out JVM optimizations that can apply to value types. This note is a thought experiment to extend the JVM’s performance model in support of value types. The demonstration has two phases.  Initially the extension can simply use design patterns, within the current bytecode architecture, and in today’s Java language. But if the performance model is to be realized in practice, it will probably require new JVM bytecode features, changes to the Java language, or both.  We will look at a few possibilities for these new features. An Axiom of Value In the context of the JVM, a value type is a data type equipped with construction, assignment, and equality operations, and a set of typed components, such that, whenever two variables of the value type produce equal corresponding values for their components, the values of the two variables cannot be distinguished by any JVM operation. Here are some corollaries: A value type is immutable, since otherwise a copy could be constructed and the original could be modified in one of its components, allowing the copies to be distinguished. Changing the component of a value type requires construction of a new value. The equals and hashCode operations are strictly component-wise. If a value type is represented by a JVM reference, that reference cannot be successfully synchronized on, and cannot be usefully compared for reference equality. A value type can be viewed in terms of what it doesn’t do. We can say that a value type omits all value-unsafe operations, which could violate the constraints on value types.  These operations, which are ordinarily allowed for Java object types, are pointer equality comparison (the acmp instruction), synchronization (the monitor instructions), all the wait and notify methods of class Object, and non-trivial finalize methods. The clone method is also value-unsafe, although for value types it could be treated as the identity function. Finally, and most importantly, any side effect on an object (however visible) also counts as an value-unsafe operation. A value type may have methods, but such methods must not change the components of the value. It is reasonable and useful to define methods like toString, equals, and hashCode on value types, and also methods which are specifically valuable to users of the value type. Representations of Value Value types have two natural representations in the JVM, unboxed and boxed. An unboxed value consists of the components, as simple variables. For example, the complex number x=(1+2i), in rectangular coordinate form, may be represented in unboxed form by the following pair of variables: /*Complex x = Complex.valueOf(1.0, 2.0):*/ double x_re = 1.0, x_im = 2.0; These variables might be locals, parameters, or fields. Their association as components of a single value is not defined to the JVM. Here is a sample computation which computes the norm of the difference between two complex numbers: double distance(/*Complex x:*/ double x_re, double x_im,         /*Complex y:*/ double y_re, double y_im) {     /*Complex z = x.minus(y):*/     double z_re = x_re - y_re, z_im = x_im - y_im;     /*return z.abs():*/     return Math.sqrt(z_re*z_re + z_im*z_im); } A boxed representation groups component values under a single object reference. The reference is to a ‘wrapper class’ that carries the component values in its fields. (A primitive type can naturally be equated with a trivial value type with just one component of that type. In that view, the wrapper class Integer can serve as a boxed representation of value type int.) The unboxed representation of complex numbers is practical for many uses, but it fails to cover several major use cases: return values, array elements, and generic APIs. The two components of a complex number cannot be directly returned from a Java function, since Java does not support multiple return values. The same story applies to array elements: Java has no ’array of structs’ feature. (Double-length arrays are a possible workaround for complex numbers, but not for value types with heterogeneous components.) By generic APIs I mean both those which use generic types, like Arrays.asList and those which have special case support for primitive types, like String.valueOf and PrintStream.println. Those APIs do not support unboxed values, and offer some problems to boxed values. Any ’real’ JVM type should have a story for returns, arrays, and API interoperability. The basic problem here is that value types fall between primitive types and object types. Value types are clearly more complex than primitive types, and object types are slightly too complicated. Objects are a little bit dangerous to use as value carriers, since object references can be compared for pointer equality, and can be synchronized on. Also, as many Java programmers have observed, there is often a performance cost to using wrapper objects, even on modern JVMs. Even so, wrapper classes are a good starting point for talking about value types. If there were a set of structural rules and restrictions which would prevent value-unsafe operations on value types, wrapper classes would provide a good notation for defining value types. This note attempts to define such rules and restrictions. Let’s Start Coding Now it is time to look at some real code. Here is a definition, written in Java, of a complex number value type. @ValueSafe public final class Complex implements java.io.Serializable {     // immutable component structure:     public final double re, im;     private Complex(double re, double im) {         this.re = re; this.im = im;     }     // interoperability methods:     public String toString() { return "Complex("+re+","+im+")"; }     public List<Double> asList() { return Arrays.asList(re, im); }     public boolean equals(Complex c) {         return re == c.re && im == c.im;     }     public boolean equals(@ValueSafe Object x) {         return x instanceof Complex && equals((Complex) x);     }     public int hashCode() {         return 31*Double.valueOf(re).hashCode()                 + Double.valueOf(im).hashCode();     }     // factory methods:     public static Complex valueOf(double re, double im) {         return new Complex(re, im);     }     public Complex changeRe(double re2) { return valueOf(re2, im); }     public Complex changeIm(double im2) { return valueOf(re, im2); }     public static Complex cast(@ValueSafe Object x) {         return x == null ? ZERO : (Complex) x;     }     // utility methods and constants:     public Complex plus(Complex c)  { return new Complex(re+c.re, im+c.im); }     public Complex minus(Complex c) { return new Complex(re-c.re, im-c.im); }     public double abs() { return Math.sqrt(re*re + im*im); }     public static final Complex PI = valueOf(Math.PI, 0.0);     public static final Complex ZERO = valueOf(0.0, 0.0); } This is not a minimal definition, because it includes some utility methods and other optional parts.  The essential elements are as follows: The class is marked as a value type with an annotation. The class is final, because it does not make sense to create subclasses of value types. The fields of the class are all non-private and final.  (I.e., the type is immutable and structurally transparent.) From the supertype Object, all public non-final methods are overridden. The constructor is private. Beyond these bare essentials, we can observe the following features in this example, which are likely to be typical of all value types: One or more factory methods are responsible for value creation, including a component-wise valueOf method. There are utility methods for complex arithmetic and instance creation, such as plus and changeIm. There are static utility constants, such as PI. The type is serializable, using the default mechanisms. There are methods for converting to and from dynamically typed references, such as asList and cast. The Rules In order to use value types properly, the programmer must avoid value-unsafe operations.  A helpful Java compiler should issue errors (or at least warnings) for code which provably applies value-unsafe operations, and should issue warnings for code which might be correct but does not provably avoid value-unsafe operations.  No such compilers exist today, but to simplify our account here, we will pretend that they do exist. A value-safe type is any class, interface, or type parameter marked with the @ValueSafe annotation, or any subtype of a value-safe type.  If a value-safe class is marked final, it is in fact a value type.  All other value-safe classes must be abstract.  The non-static fields of a value class must be non-public and final, and all its constructors must be private. Under the above rules, a standard interface could be helpful to define value types like Complex.  Here is an example: @ValueSafe public interface ValueType extends java.io.Serializable {     // All methods listed here must get redefined.     // Definitions must be value-safe, which means     // they may depend on component values only.     List<? extends Object> asList();     int hashCode();     boolean equals(@ValueSafe Object c);     String toString(); } //@ValueSafe inherited from supertype: public final class Complex implements ValueType { … The main advantage of such a conventional interface is that (unlike an annotation) it is reified in the runtime type system.  It could appear as an element type or parameter bound, for facilities which are designed to work on value types only.  More broadly, it might assist the JVM to perform dynamic enforcement of the rules for value types. Besides types, the annotation @ValueSafe can mark fields, parameters, local variables, and methods.  (This is redundant when the type is also value-safe, but may be useful when the type is Object or another supertype of a value type.)  Working forward from these annotations, an expression E is defined as value-safe if it satisfies one or more of the following: The type of E is a value-safe type. E names a field, parameter, or local variable whose declaration is marked @ValueSafe. E is a call to a method whose declaration is marked @ValueSafe. E is an assignment to a value-safe variable, field reference, or array reference. E is a cast to a value-safe type from a value-safe expression. E is a conditional expression E0 ? E1 : E2, and both E1 and E2 are value-safe. Assignments to value-safe expressions and initializations of value-safe names must take their values from value-safe expressions. A value-safe expression may not be the subject of a value-unsafe operation.  In particular, it cannot be synchronized on, nor can it be compared with the “==” operator, not even with a null or with another value-safe type. In a program where all of these rules are followed, no value-type value will be subject to a value-unsafe operation.  Thus, the prime axiom of value types will be satisfied, that no two value type will be distinguishable as long as their component values are equal. More Code To illustrate these rules, here are some usage examples for Complex: Complex pi = Complex.valueOf(Math.PI, 0); Complex zero = pi.changeRe(0);  //zero = pi; zero.re = 0; ValueType vtype = pi; @SuppressWarnings("value-unsafe")   Object obj = pi; @ValueSafe Object obj2 = pi; obj2 = new Object();  // ok List<Complex> clist = new ArrayList<Complex>(); clist.add(pi);  // (ok assuming List.add param is @ValueSafe) List<ValueType> vlist = new ArrayList<ValueType>(); vlist.add(pi);  // (ok) List<Object> olist = new ArrayList<Object>(); olist.add(pi);  // warning: "value-unsafe" boolean z = pi.equals(zero); boolean z1 = (pi == zero);  // error: reference comparison on value type boolean z2 = (pi == null);  // error: reference comparison on value type boolean z3 = (pi == obj2);  // error: reference comparison on value type synchronized (pi) { }  // error: synch of value, unpredictable result synchronized (obj2) { }  // unpredictable result Complex qq = pi; qq = null;  // possible NPE; warning: “null-unsafe" qq = (Complex) obj;  // warning: “null-unsafe" qq = Complex.cast(obj);  // OK @SuppressWarnings("null-unsafe")   Complex empty = null;  // possible NPE qq = empty;  // possible NPE (null pollution) The Payoffs It follows from this that either the JVM or the java compiler can replace boxed value-type values with unboxed ones, without affecting normal computations.  Fields and variables of value types can be split into their unboxed components.  Non-static methods on value types can be transformed into static methods which take the components as value parameters. Some common questions arise around this point in any discussion of value types. Why burden the programmer with all these extra rules?  Why not detect programs automagically and perform unboxing transparently?  The answer is that it is easy to break the rules accidently unless they are agreed to by the programmer and enforced.  Automatic unboxing optimizations are tantalizing but (so far) unreachable ideal.  In the current state of the art, it is possible exhibit benchmarks in which automatic unboxing provides the desired effects, but it is not possible to provide a JVM with a performance model that assures the programmer when unboxing will occur.  This is why I’m writing this note, to enlist help from, and provide assurances to, the programmer.  Basically, I’m shooting for a good set of user-supplied “pragmas” to frame the desired optimization. Again, the important thing is that the unboxing must be done reliably, or else programmers will have no reason to work with the extra complexity of the value-safety rules.  There must be a reasonably stable performance model, wherein using a value type has approximately the same performance characteristics as writing the unboxed components as separate Java variables. There are some rough corners to the present scheme.  Since Java fields and array elements are initialized to null, value-type computations which incorporate uninitialized variables can produce null pointer exceptions.  One workaround for this is to require such variables to be null-tested, and the result replaced with a suitable all-zero value of the value type.  That is what the “cast” method does above. Generically typed APIs like List<T> will continue to manipulate boxed values always, at least until we figure out how to do reification of generic type instances.  Use of such APIs will elicit warnings until their type parameters (and/or relevant members) are annotated or typed as value-safe.  Retrofitting List<T> is likely to expose flaws in the present scheme, which we will need to engineer around.  Here are a couple of first approaches: public interface java.util.List<@ValueSafe T> extends Collection<T> { … public interface java.util.List<T extends Object|ValueType> extends Collection<T> { … (The second approach would require disjunctive types, in which value-safety is “contagious” from the constituent types.) With more transformations, the return value types of methods can also be unboxed.  This may require significant bytecode-level transformations, and would work best in the presence of a bytecode representation for multiple value groups, which I have proposed elsewhere under the title “Tuples in the VM”. But for starters, the JVM can apply this transformation under the covers, to internally compiled methods.  This would give a way to express multiple return values and structured return values, which is a significant pain-point for Java programmers, especially those who work with low-level structure types favored by modern vector and graphics processors.  The lack of multiple return values has a strong distorting effect on many Java APIs. Even if the JVM fails to unbox a value, there is still potential benefit to the value type.  Clustered computing systems something have copy operations (serialization or something similar) which apply implicitly to command operands.  When copying JVM objects, it is extremely helpful to know when an object’s identity is important or not.  If an object reference is a copied operand, the system may have to create a proxy handle which points back to the original object, so that side effects are visible.  Proxies must be managed carefully, and this can be expensive.  On the other hand, value types are exactly those types which a JVM can “copy and forget” with no downside. Array types are crucial to bulk data interfaces.  (As data sizes and rates increase, bulk data becomes more important than scalar data, so arrays are definitely accompanying us into the future of computing.)  Value types are very helpful for adding structure to bulk data, so a successful value type mechanism will make it easier for us to express richer forms of bulk data. Unboxing arrays (i.e., arrays containing unboxed values) will provide better cache and memory density, and more direct data movement within clustered or heterogeneous computing systems.  They require the deepest transformations, relative to today’s JVM.  There is an impedance mismatch between value-type arrays and Java’s covariant array typing, so compromises will need to be struck with existing Java semantics.  It is probably worth the effort, since arrays of unboxed value types are inherently more memory-efficient than standard Java arrays, which rely on dependent pointer chains. It may be sufficient to extend the “value-safe” concept to array declarations, and allow low-level transformations to change value-safe array declarations from the standard boxed form into an unboxed tuple-based form.  Such value-safe arrays would not be convertible to Object[] arrays.  Certain connection points, such as Arrays.copyOf and System.arraycopy might need additional input/output combinations, to allow smooth conversion between arrays with boxed and unboxed elements. Alternatively, the correct solution may have to wait until we have enough reification of generic types, and enough operator overloading, to enable an overhaul of Java arrays. Implicit Method Definitions The example of class Complex above may be unattractively complex.  I believe most or all of the elements of the example class are required by the logic of value types. If this is true, a programmer who writes a value type will have to write lots of error-prone boilerplate code.  On the other hand, I think nearly all of the code (except for the domain-specific parts like plus and minus) can be implicitly generated. Java has a rule for implicitly defining a class’s constructor, if no it defines no constructors explicitly.  Likewise, there are rules for providing default access modifiers for interface members.  Because of the highly regular structure of value types, it might be reasonable to perform similar implicit transformations on value types.  Here’s an example of a “highly implicit” definition of a complex number type: public class Complex implements ValueType {  // implicitly final     public double re, im;  // implicitly public final     //implicit methods are defined elementwise from te fields:     //  toString, asList, equals(2), hashCode, valueOf, cast     //optionally, explicit methods (plus, abs, etc.) would go here } In other words, with the right defaults, a simple value type definition can be a one-liner.  The observant reader will have noticed the similarities (and suitable differences) between the explicit methods above and the corresponding methods for List<T>. Another way to abbreviate such a class would be to make an annotation the primary trigger of the functionality, and to add the interface(s) implicitly: public @ValueType class Complex { … // implicitly final, implements ValueType (But to me it seems better to communicate the “magic” via an interface, even if it is rooted in an annotation.) Implicitly Defined Value Types So far we have been working with nominal value types, which is to say that the sequence of typed components is associated with a name and additional methods that convey the intention of the programmer.  A simple ordered pair of floating point numbers can be variously interpreted as (to name a few possibilities) a rectangular or polar complex number or Cartesian point.  The name and the methods convey the intended meaning. But what if we need a truly simple ordered pair of floating point numbers, without any further conceptual baggage?  Perhaps we are writing a method (like “divideAndRemainder”) which naturally returns a pair of numbers instead of a single number.  Wrapping the pair of numbers in a nominal type (like “QuotientAndRemainder”) makes as little sense as wrapping a single return value in a nominal type (like “Quotient”).  What we need here are structural value types commonly known as tuples. For the present discussion, let us assign a conventional, JVM-friendly name to tuples, roughly as follows: public class java.lang.tuple.$DD extends java.lang.tuple.Tuple {      double $1, $2; } Here the component names are fixed and all the required methods are defined implicitly.  The supertype is an abstract class which has suitable shared declarations.  The name itself mentions a JVM-style method parameter descriptor, which may be “cracked” to determine the number and types of the component fields. The odd thing about such a tuple type (and structural types in general) is it must be instantiated lazily, in response to linkage requests from one or more classes that need it.  The JVM and/or its class loaders must be prepared to spin a tuple type on demand, given a simple name reference, $xyz, where the xyz is cracked into a series of component types.  (Specifics of naming and name mangling need some tasteful engineering.) Tuples also seem to demand, even more than nominal types, some support from the language.  (This is probably because notations for non-nominal types work best as combinations of punctuation and type names, rather than named constructors like Function3 or Tuple2.)  At a minimum, languages with tuples usually (I think) have some sort of simple bracket notation for creating tuples, and a corresponding pattern-matching syntax (or “destructuring bind”) for taking tuples apart, at least when they are parameter lists.  Designing such a syntax is no simple thing, because it ought to play well with nominal value types, and also with pre-existing Java features, such as method parameter lists, implicit conversions, generic types, and reflection.  That is a task for another day. Other Use Cases Besides complex numbers and simple tuples there are many use cases for value types.  Many tuple-like types have natural value-type representations. These include rational numbers, point locations and pixel colors, and various kinds of dates and addresses. Other types have a variable-length ‘tail’ of internal values. The most common example of this is String, which is (mathematically) a sequence of UTF-16 character values. Similarly, bit vectors, multiple-precision numbers, and polynomials are composed of sequences of values. Such types include, in their representation, a reference to a variable-sized data structure (often an array) which (somehow) represents the sequence of values. The value type may also include ’header’ information. Variable-sized values often have a length distribution which favors short lengths. In that case, the design of the value type can make the first few values in the sequence be direct ’header’ fields of the value type. In the common case where the header is enough to represent the whole value, the tail can be a shared null value, or even just a null reference. Note that the tail need not be an immutable object, as long as the header type encapsulates it well enough. This is the case with String, where the tail is a mutable (but never mutated) character array. Field types and their order must be a globally visible part of the API.  The structure of the value type must be transparent enough to have a globally consistent unboxed representation, so that all callers and callees agree about the type and order of components  that appear as parameters, return types, and array elements.  This is a trade-off between efficiency and encapsulation, which is forced on us when we remove an indirection enjoyed by boxed representations.  A JVM-only transformation would not care about such visibility, but a bytecode transformation would need to take care that (say) the components of complex numbers would not get swapped after a redefinition of Complex and a partial recompile.  Perhaps constant pool references to value types need to declare the field order as assumed by each API user. This brings up the delicate status of private fields in a value type.  It must always be possible to load, store, and copy value types as coordinated groups, and the JVM performs those movements by moving individual scalar values between locals and stack.  If a component field is not public, what is to prevent hostile code from plucking it out of the tuple using a rogue aload or astore instruction?  Nothing but the verifier, so we may need to give it more smarts, so that it treats value types as inseparable groups of stack slots or locals (something like long or double). My initial thought was to make the fields always public, which would make the security problem moot.  But public is not always the right answer; consider the case of String, where the underlying mutable character array must be encapsulated to prevent security holes.  I believe we can win back both sides of the tradeoff, by training the verifier never to split up the components in an unboxed value.  Just as the verifier encapsulates the two halves of a 64-bit primitive, it can encapsulate the the header and body of an unboxed String, so that no code other than that of class String itself can take apart the values. Similar to String, we could build an efficient multi-precision decimal type along these lines: public final class DecimalValue extends ValueType {     protected final long header;     protected private final BigInteger digits;     public DecimalValue valueOf(int value, int scale) {         assert(scale >= 0);         return new DecimalValue(((long)value << 32) + scale, null);     }     public DecimalValue valueOf(long value, int scale) {         if (value == (int) value)             return valueOf((int)value, scale);         return new DecimalValue(-scale, new BigInteger(value));     } } Values of this type would be passed between methods as two machine words. Small values (those with a significand which fits into 32 bits) would be represented without any heap data at all, unless the DecimalValue itself were boxed. (Note the tension between encapsulation and unboxing in this case.  It would be better if the header and digits fields were private, but depending on where the unboxing information must “leak”, it is probably safer to make a public revelation of the internal structure.) Note that, although an array of Complex can be faked with a double-length array of double, there is no easy way to fake an array of unboxed DecimalValues.  (Either an array of boxed values or a transposed pair of homogeneous arrays would be reasonable fallbacks, in a current JVM.)  Getting the full benefit of unboxing and arrays will require some new JVM magic. Although the JVM emphasizes portability, system dependent code will benefit from using machine-level types larger than 64 bits.  For example, the back end of a linear algebra package might benefit from value types like Float4 which map to stock vector types.  This is probably only worthwhile if the unboxing arrays can be packed with such values. More Daydreams A more finely-divided design for dynamic enforcement of value safety could feature separate marker interfaces for each invariant.  An empty marker interface Unsynchronizable could cause suitable exceptions for monitor instructions on objects in marked classes.  More radically, a Interchangeable marker interface could cause JVM primitives that are sensitive to object identity to raise exceptions; the strangest result would be that the acmp instruction would have to be specified as raising an exception. @ValueSafe public interface ValueType extends java.io.Serializable,         Unsynchronizable, Interchangeable { … public class Complex implements ValueType {     // inherits Serializable, Unsynchronizable, Interchangeable, @ValueSafe     … It seems possible that Integer and the other wrapper types could be retro-fitted as value-safe types.  This is a major change, since wrapper objects would be unsynchronizable and their references interchangeable.  It is likely that code which violates value-safety for wrapper types exists but is uncommon.  It is less plausible to retro-fit String, since the prominent operation String.intern is often used with value-unsafe code. We should also reconsider the distinction between boxed and unboxed values in code.  The design presented above obscures that distinction.  As another thought experiment, we could imagine making a first class distinction in the type system between boxed and unboxed representations.  Since only primitive types are named with a lower-case initial letter, we could define that the capitalized version of a value type name always refers to the boxed representation, while the initial lower-case variant always refers to boxed.  For example: complex pi = complex.valueOf(Math.PI, 0); Complex boxPi = pi;  // convert to boxed myList.add(boxPi); complex z = myList.get(0);  // unbox Such a convention could perhaps absorb the current difference between int and Integer, double and Double. It might also allow the programmer to express a helpful distinction among array types. As said above, array types are crucial to bulk data interfaces, but are limited in the JVM.  Extending arrays beyond the present limitations is worth thinking about; for example, the Maxine JVM implementation has a hybrid object/array type.  Something like this which can also accommodate value type components seems worthwhile.  On the other hand, does it make sense for value types to contain short arrays?  And why should random-access arrays be the end of our design process, when bulk data is often sequentially accessed, and it might make sense to have heterogeneous streams of data as the natural “jumbo” data structure.  These considerations must wait for another day and another note. More Work It seems to me that a good sequence for introducing such value types would be as follows: Add the value-safety restrictions to an experimental version of javac. Code some sample applications with value types, including Complex and DecimalValue. Create an experimental JVM which internally unboxes value types but does not require new bytecodes to do so.  Ensure the feasibility of the performance model for the sample applications. Add tuple-like bytecodes (with or without generic type reification) to a major revision of the JVM, and teach the Java compiler to switch in the new bytecodes without code changes. A staggered roll-out like this would decouple language changes from bytecode changes, which is always a convenient thing. A similar investigation should be applied (concurrently) to array types.  In this case, it seems to me that the starting point is in the JVM: Add an experimental unboxing array data structure to a production JVM, perhaps along the lines of Maxine hybrids.  No bytecode or language support is required at first; everything can be done with encapsulated unsafe operations and/or method handles. Create an experimental JVM which internally unboxes value types but does not require new bytecodes to do so.  Ensure the feasibility of the performance model for the sample applications. Add tuple-like bytecodes (with or without generic type reification) to a major revision of the JVM, and teach the Java compiler to switch in the new bytecodes without code changes. That’s enough musing me for now.  Back to work!

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• Why keylistener is not working here?

  - by swift

  i have implemented keylistener interface and implemented all the needed methods but when i press the key nothing happens here, why? package swing; import java.awt.Color; import java.awt.Dimension; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.GridLayout; import java.awt.Point; import java.awt.RenderingHints; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.KeyEvent; import java.awt.event.KeyListener; import java.awt.event.MouseEvent; import java.awt.event.MouseListener; import java.awt.event.MouseMotionListener; import java.awt.event.WindowAdapter; import java.awt.event.WindowEvent; import java.awt.image.BufferedImage; import javax.swing.BorderFactory; import javax.swing.BoxLayout; import javax.swing.ImageIcon; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JLayeredPane; import javax.swing.JPanel; import javax.swing.JTextArea; class Paper extends JPanel implements MouseListener,MouseMotionListener,ActionListener,KeyListener { static BufferedImage image; String shape; Color color=Color.black; Point start; Point end; Point mp; Button elipse=new Button("elipse"); int x[]=new int[50]; int y[]=new int[50]; Button rectangle=new Button("rect"); Button line=new Button("line"); Button roundrect=new Button("roundrect"); Button polygon=new Button("poly"); Button text=new Button("text"); ImageIcon erasericon=new ImageIcon("images/eraser.gif"); JButton erase=new JButton(erasericon); JButton[] colourbutton=new JButton[9]; String selected; Point label; String key; int ex,ey;//eraser //DatagramSocket dataSocket; JButton button = new JButton("test"); JLayeredPane layerpane; Point p=new Point(); int w,h; public Paper() { JFrame frame=new JFrame("Whiteboard"); frame.setVisible(true); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setSize(640, 480); frame.setBackground(Color.black); layerpane=frame.getLayeredPane(); setWidth(539,444); setBounds(69,0,555,444); layerpane.add(this,new Integer(2)); layerpane.add(this.addButtons(),new Integer(0)); setLayout(null); setOpaque(false); addMouseListener(this); addMouseMotionListener(this); setFocusable(true); addKeyListener(this); System.out.println(isFocusable()); setBorder(BorderFactory.createLineBorder(Color.black)); } public void paintComponent(Graphics g) { try { super.paintComponent(g); g.drawImage(image, 0, 0, this); Graphics2D g2 = (Graphics2D)g; if(color!=null) g2.setPaint(color); if(start!=null && end!=null) { if(selected==("elipse")) g2.drawOval(start.x, start.y,(end.x-start.x),(end.y-start.y)); else if(selected==("rect")) g2.drawRect(start.x, start.y, (end.x-start.x),(end.y-start.y)); else if(selected==("rrect")) g2.drawRoundRect(start.x, start.y, (end.x-start.x),(end.y-start.y),11,11); else if(selected==("line")) g2.drawLine(start.x,start.y,end.x,end.y); else if(selected==("poly")) g2.drawPolygon(x,y,2); } } catch(Exception e) {} } //Function to draw the shape on image public void draw() { Graphics2D g2 = image.createGraphics(); g2.setPaint(color); if(start!=null && end!=null) { if(selected=="line") g2.drawLine(start.x, start.y, end.x, end.y); else if(selected=="elipse") g2.drawOval(start.x, start.y, (end.x-start.x),(end.y-start.y)); else if(selected=="rect") g2.drawRect(start.x, start.y, (end.x-start.x),(end.y-start.y)); else if(selected==("rrect")) g2.drawRoundRect(start.x, start.y, (end.x-start.x),(end.y-start.y),11,11); else if(selected==("poly")) g2.drawPolygon(x,y,2); } if(label!=null) { JTextArea textarea=new JTextArea(); if(selected==("text")) { textarea.setBounds(label.x, label.y, 50, 50); textarea.setMaximumSize(new Dimension(100,100)); textarea.setBackground(new Color(237,237,237)); add(textarea); g2.drawString("key",label.x,label.y); } } start=null; repaint(); g2.dispose(); } public void text() { System.out.println(label); } //Function which provides the erase functionality public void erase() { Graphics2D pic=(Graphics2D) image.getGraphics(); Color erasecolor=new Color(237,237,237); pic.setPaint(erasecolor); if(start!=null) pic.fillRect(start.x, start.y, 10, 10); } //To set the size of the image public void setWidth(int x,int y) { System.out.println("("+x+","+y+")"); w=x; h=y; image = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB); } //Function to add buttons into the panel, calling this function returns a panel public JPanel addButtons() { JPanel buttonpanel=new JPanel(); buttonpanel.setMaximumSize(new Dimension(70,70)); JPanel shape=new JPanel(); JPanel colourbox=new JPanel(); shape.setLayout(new GridLayout(4,2)); shape.setMaximumSize(new Dimension(70,140)); colourbox.setLayout(new GridLayout(3,3)); colourbox.setMaximumSize(new Dimension(70,70)); buttonpanel.setLayout(new BoxLayout(buttonpanel,BoxLayout.Y_AXIS)); elipse.addActionListener(this); elipse.setToolTipText("Elipse"); rectangle.addActionListener(this); rectangle.setToolTipText("Rectangle"); line.addActionListener( this); line.setToolTipText("Line"); erase.addActionListener(this); erase.setToolTipText("Eraser"); roundrect.addActionListener(this); roundrect.setToolTipText("Round rect"); polygon.addActionListener(this); polygon.setToolTipText("Polygon"); text.addActionListener(this); text.setToolTipText("Text"); shape.add(elipse); shape.add(rectangle); shape.add(line); shape.add(erase); shape.add(roundrect); shape.add(polygon); shape.add(text); buttonpanel.add(shape); for(int i=0;i<9;i++) { colourbutton[i]=new JButton(); colourbox.add(colourbutton[i]); if(i==0) colourbutton[0].setBackground(Color.black); else if(i==1) colourbutton[1].setBackground(Color.white); else if(i==2) colourbutton[2].setBackground(Color.red); else if(i==3) colourbutton[3].setBackground(Color.orange); else if(i==4) colourbutton[4].setBackground(Color.blue); else if(i==5) colourbutton[5].setBackground(Color.green); else if(i==6) colourbutton[6].setBackground(Color.pink); else if(i==7) colourbutton[7].setBackground(Color.magenta); else if(i==8) colourbutton[8].setBackground(Color.cyan); colourbutton[i].addActionListener(this); } buttonpanel.add(colourbox); buttonpanel.setBounds(0, 0, 70, 210); return buttonpanel; } public void mouseClicked(MouseEvent e) { if(selected=="text") { label=new Point(); label=e.getPoint(); draw(); } } @Override public void mouseEntered(MouseEvent arg0) { } public void mouseExited(MouseEvent arg0) { } public void mousePressed(MouseEvent e) { if(selected=="line"||selected=="erase"||selected=="text") { start=e.getPoint(); } else if(selected=="elipse"||selected=="rect"||selected=="rrect") { mp = e.getPoint(); } else if(selected=="poly") { x[0]=e.getX(); y[0]=e.getY(); } } public void mouseReleased(MouseEvent e) { if(start!=null) { if(selected=="line") { end=e.getPoint(); } else if(selected=="elipse"||selected=="rect"||selected=="rrect") { end.x = Math.max(mp.x,e.getX()); end.y = Math.max(mp.y,e.getY()); } else if(selected=="poly") { x[1]=e.getX(); y[1]=e.getY(); } draw(); } } public void mouseDragged(MouseEvent e) { if(end==null) end = new Point(); if(start==null) start = new Point(); if(selected=="line") { end=e.getPoint(); } else if(selected=="erase") { start=e.getPoint(); erase(); } else if(selected=="elipse"||selected=="rect"||selected=="rrect") { start.x = Math.min(mp.x,e.getX()); start.y = Math.min(mp.y,e.getY()); end.x = Math.max(mp.x,e.getX()); end.y = Math.max(mp.y,e.getY()); } else if(selected=="poly") { x[1]=e.getX(); y[1]=e.getY(); } repaint(); } public void mouseMoved(MouseEvent arg0) {} public void actionPerformed(ActionEvent e) { if(e.getSource()==elipse) selected="elipse"; else if(e.getSource()==line) selected="line"; else if(e.getSource()==rectangle) selected="rect"; else if(e.getSource()==erase) { selected="erase"; System.out.println(selected); erase(); } else if(e.getSource()==roundrect) selected="rrect"; else if(e.getSource()==polygon) selected="poly"; else if(e.getSource()==text) selected="text"; if(e.getSource()==colourbutton[0]) color=Color.black; else if(e.getSource()==colourbutton[1]) color=Color.white; else if(e.getSource()==colourbutton[2]) color=Color.red; else if(e.getSource()==colourbutton[3]) color=Color.orange; else if(e.getSource()==colourbutton[4]) color=Color.blue; else if(e.getSource()==colourbutton[5]) color=Color.green; else if(e.getSource()==colourbutton[6]) color=Color.pink; else if(e.getSource()==colourbutton[7]) color=Color.magenta; else if(e.getSource()==colourbutton[8]) color=Color.cyan; } @Override public void keyPressed(KeyEvent e) { System.out.println("pressed"); } @Override public void keyReleased(KeyEvent e) { System.out.println("key released"); } @Override public void keyTyped(KeyEvent e) { System.out.println("Typed"); } public static void main(String[] a) { new Paper(); } } class Button extends JButton { String name; public Button(String name) { this.name=name; } public void paintComponent(Graphics g) { super.paintComponent(g); Graphics2D g2 = (Graphics2D)g; g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON); //g2.setStroke(new BasicStroke(1.2f)); if (name == "line") g.drawLine(5,5,30,30); if (name == "elipse") g.drawOval(5,7,25,20); if (name== "rect") g.drawRect(5,5,25,23); if (name== "roundrect") g.drawRoundRect(5,5,25,23,10,10); int a[]=new int[]{20,9,20,23,20}; int b[]=new int[]{9,23,25,20,9}; if (name== "poly") g.drawPolyline(a, b, 5); if (name== "text") g.drawString("Text",5, 22); } }

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• please help turn a simple Python2 code to PHP

  - by user296516

  Hi guys, Sorry to bother again, but I really need help transforming this Python2 code into PHP. net, cid, lac = 25002, 9164, 4000 import urllib a = '000E00000000000000000000000000001B0000000000000000000000030000' b = hex(cid)[2:].zfill(8) + hex(lac)[2:].zfill(8) c = hex(divmod(net,100)[1])[2:].zfill(8) + hex(divmod(net,100)[0])[2:].zfill(8) string = (a + b + c + 'FFFFFFFF00000000').decode('hex') data = urllib.urlopen('http://www.google.com/glm/mmap',string) r = data.read().encode('hex') print float(int(r[14:22],16))/1000000, float(int(r[22:30],16))/1000000 Would be great if someone could help, thanks in advance!

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• nonparametric regression method using R

  - by user1782652

  I need to find the certain driver variables for unit sales & their impact on sales. My data is such data the error does not follow normal distribution & the unit sales is also not following any particular statistical distribution. Given such condition, it is difficult for me to use simple liner regression or GLM. Can any of you please suggest me some non parametric regression technique which I can use in R to model the relationship? Thanks,

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• C# 4.0: Dynamic Programming

  - by Paulo Morgado

  The major feature of C# 4.0 is dynamic programming. Not just dynamic typing, but dynamic in broader sense, which means talking to anything that is not statically typed to be a .NET object. Dynamic Language Runtime The Dynamic Language Runtime (DLR) is piece of technology that unifies dynamic programming on the .NET platform, the same way the Common Language Runtime (CLR) has been a common platform for statically typed languages. The CLR always had dynamic capabilities. You could always use reflection, but its main goal was never to be a dynamic programming environment and there were some features missing. The DLR is built on top of the CLR and adds those missing features to the .NET platform. The Dynamic Language Runtime is the core infrastructure that consists of: Expression Trees The same expression trees used in LINQ, now improved to support statements. Dynamic Dispatch Dispatches invocations to the appropriate binder. Call Site Caching For improved efficiency. Dynamic languages and languages with dynamic capabilities are built on top of the DLR. IronPython and IronRuby were already built on top of the DLR, and now, the support for using the DLR is being added to C# and Visual Basic. Other languages built on top of the CLR are expected to also use the DLR in the future. Underneath the DLR there are binders that talk to a variety of different technologies: .NET Binder Allows to talk to .NET objects. JavaScript Binder Allows to talk to JavaScript in SilverLight. IronPython Binder Allows to talk to IronPython. IronRuby Binder Allows to talk to IronRuby. COM Binder Allows to talk to COM. Whit all these binders it is possible to have a single programming experience to talk to all these environments that are not statically typed .NET objects. The dynamic Static Type Let’s take this traditional statically typed code: Calculator calculator = GetCalculator(); int sum = calculator.Sum(10, 20); Because the variable that receives the return value of the GetCalulator method is statically typed to be of type Calculator and, because the Calculator type has an Add method that receives two integers and returns an integer, it is possible to call that Sum method and assign its return value to a variable statically typed as integer. Now lets suppose the calculator was not a statically typed .NET class, but, instead, a COM object or some .NET code we don’t know he type of. All of the sudden it gets very painful to call the Add method: object calculator = GetCalculator(); Type calculatorType = calculator.GetType(); object res = calculatorType.InvokeMember("Add", BindingFlags.InvokeMethod, null, calculator, new object[] { 10, 20 }); int sum = Convert.ToInt32(res); And what if the calculator was a JavaScript object? ScriptObject calculator = GetCalculator(); object res = calculator.Invoke("Add", 10, 20); int sum = Convert.ToInt32(res); For each dynamic domain we have a different programming experience and that makes it very hard to unify the code. With C# 4.0 it becomes possible to write code this way: dynamic calculator = GetCalculator(); int sum = calculator.Add(10, 20); You simply declare a variable who’s static type is dynamic. dynamic is a pseudo-keyword (like var) that indicates to the compiler that operations on the calculator object will be done dynamically. The way you should look at dynamic is that it’s just like object (System.Object) with dynamic semantics associated. Anything can be assigned to a dynamic. dynamic x = 1; dynamic y = "Hello"; dynamic z = new List<int> { 1, 2, 3 }; At run-time, all object will have a type. In the above example x is of type System.Int32. When one or more operands in an operation are typed dynamic, member selection is deferred to run-time instead of compile-time. Then the run-time type is substituted in all variables and normal overload resolution is done, just like it would happen at compile-time. The result of any dynamic operation is always dynamic and, when a dynamic object is assigned to something else, a dynamic conversion will occur. Code Resolution Method double x = 1.75; double y = Math.Abs(x); compile-time double Abs(double x) dynamic x = 1.75; dynamic y = Math.Abs(x); run-time double Abs(double x) dynamic x = 2; dynamic y = Math.Abs(x); run-time int Abs(int x) The above code will always be strongly typed. The difference is that, in the first case the method resolution is done at compile-time, and the others it’s done ate run-time. IDynamicMetaObjectObject The DLR is pre-wired to know .NET objects, COM objects and so forth but any dynamic language can implement their own objects or you can implement your own objects in C# through the implementation of the IDynamicMetaObjectProvider interface. When an object implements IDynamicMetaObjectProvider, it can participate in the resolution of how method calls and property access is done. The .NET Framework already provides two implementations of IDynamicMetaObjectProvider: DynamicObject : IDynamicMetaObjectProvider The DynamicObject class enables you to define which operations can be performed on dynamic objects and how to perform those operations. For example, you can define what happens when you try to get or set an object property, call a method, or perform standard mathematical operations such as addition and multiplication. ExpandoObject : IDynamicMetaObjectProvider The ExpandoObject class enables you to add and delete members of its instances at run time and also to set and get values of these members. This class supports dynamic binding, which enables you to use standard syntax like sampleObject.sampleMember, instead of more complex syntax like sampleObject.GetAttribute("sampleMember").

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• What Counts For a DBA: Simplicity

  - by Louis Davidson

  Too many computer processes do an apparently simple task in a bizarrely complex way. They remind me of this strip by one of my favorite artists: Rube Goldberg. In order to keep the boss from knowing one was late, a process is devised whereby the cuckoo clock kisses a live cuckoo bird, who then pulls a string, which triggers a hat flinging, which in turn lands on a rod that removes a typewriter cover…and so on. We rely on creating automated processes to keep on top of tasks. DBAs have a lot of tasks to perform: backups, performance tuning, data movement, system monitoring, and of course, avoiding being noticed.  Every day, there are many steps to perform to maintain the database infrastructure, including: checking physical structures, re-indexing tables where needed, backing up the databases, checking those backups, running the ETL, and preparing the daily reports and yes, all of these processes have to complete before you can call it a day, and probably before many others have started that same day. Some of these tasks are just naturally complicated on their own. Other tasks become complicated because the database architecture is excessively rigid, and we often discover during “production testing” that certain processes need to be changed because the written requirements barely resembled the actual customer requirements.   Then, with no time to change that rigid structure, we are forced to heap layer upon layer of code onto the problematic processes. Instead of a slight table change and a new index, we end up with 4 new ETL processes, 20 temp tables, 30 extra queries, and 1000 lines of SQL code.  Report writers then need to build reports and make magical numbers appear from those toxic data structures that are overly complex and probably filled with inconsistent data. What starts out as a collection of fairly simple tasks turns into a Goldbergian nightmare of daily processes that are likely to cause your dinner to be interrupted by the smartphone doing the vibration dance that signifies trouble at the mill. So what to do? Well, if it is at all possible, simplify the problem by either going into the code and refactoring the complex code to simple, or taking all of the processes and simplifying them into small, independent, easily-tested steps.  The former approach usually requires an agreement on changing underlying structures that requires countless mind-numbing meetings; while the latter can generally be done to any complex process without the same frustration or anger, though it will still leave you with lots of steps to complete, the ability to test each step independently will definitely increase the quality of the overall process (and with each step reporting status back, finding an actual problem within the process will be definitely less unpleasant.) We all know the principle behind simplifying a sequence of processes because we learned it in math classes in our early years of attending school, starting with elementary school. In my 4 years (ok, 9 years) of undergraduate work, I remember pretty much one thing from my many math classes that I apply daily to my career as a data architect, data programmer, and as an occasional indentured DBA: “show your work”. This process of showing your work was my first lesson in simplification. Each step in the process was in fact, far simpler than the entire process.  When you were working an equation that took both sides of 4 sheets of paper, showing your work was important because the teacher could see every step, judge it, and mark it accordingly.  So often I would make an error in the first few lines of a problem which meant that the rest of the work was actually moving me closer to a very wrong answer, no matter how correct the math was in the subsequent steps. Yet, when I got my grade back, I would sometimes be pleasantly surprised. I passed, yet missed every problem on the test. But why? While I got the fact that 1+1=2 wrong in every problem, the teacher could see that I was using the right process. In a computer process, the process is very similar. We take complex processes, show our work by storing intermediate values, and test each step independently. When a process has 100 steps, each step becomes a simple step that is tested and verified, such that there will be 100 places where data is stored, validated, and can be checked off as complete. If you get step 1 of 100 wrong, you can fix it and be confident (that if you did your job of testing the other steps better than the one you had to repair,) that the rest of the process works. If you have 100 steps, and store the state of the process exactly once, the resulting testable chunk of code will be far more complex and finding the error will require checking all 100 steps as one, and usually it would be easier to find a specific needle in a stack of similarly shaped needles.  The goal is to strive for simplicity either in the solution, or at least by simplifying every process down to as many, independent, testable, simple tasks as possible.  For the tasks that really can’t be done completely independently, minimally take those tasks and break them down into simpler steps that can be tested independently.  Like working out division problems longhand, have each step of the larger problem verified and tested.

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• Extreme Optimization – Numerical Algorithm Support

  - by JoshReuben

  Function Delegates Many calculations involve the repeated evaluation of one or more user-supplied functions eg Numerical integration. The EO MathLib provides delegate types for common function signatures and the FunctionFactory class can generate new delegates from existing ones. RealFunction delegate - takes one Double parameter – can encapsulate most of the static methods of the System.Math class, as well as the classes in the Extreme.Mathematics.SpecialFunctions namespace: var sin = new RealFunction(Math.Sin); var result = sin(1); BivariateRealFunction delegate - takes two Double parameters: var atan2 = new BivariateRealFunction (Math.Atan2); var result = atan2(1, 2); TrivariateRealFunction delegate – represents a function takes three Double arguments ParameterizedRealFunction delegate - represents a function taking one Integer and one Double argument that returns a real number. The Pow method implements such a function, but the arguments need order re-arrangement: static double Power(int exponent, double x) { return ElementaryFunctions.Pow(x, exponent); } ... var power = new ParameterizedRealFunction(Power); var result = power(6, 3.2); A ComplexFunction delegate - represents a function that takes an Extreme.Mathematics.DoubleComplex argument and also returns a complex number. MultivariateRealFunction delegate - represents a function that takes an Extreme.Mathematics.LinearAlgebra.Vector argument and returns a real number. MultivariateVectorFunction delegate - represents a function that takes a Vector argument and returns a Vector. FastMultivariateVectorFunction delegate - represents a function that takes an input Vector argument and an output Matrix argument – avoiding object construction  The FunctionFactory class RealFromBivariateRealFunction and RealFromParameterizedRealFunction helper methods - transform BivariateRealFunction or a ParameterizedRealFunction into a RealFunction delegate by fixing one of the arguments, and treating this as a new function of a single argument. var tenthPower = FunctionFactory.RealFromParameterizedRealFunction(power, 10); var result = tenthPower(x); Note: There is no direct way to do this programmatically in C# - in F# you have partial value functions where you supply a subset of the arguments (as a travelling closure) that the function expects. When you omit arguments, F# generates a new function that holds onto/remembers the arguments you passed in and "waits" for the other parameters to be supplied. let sumVals x y = x + y     let sumX = sumVals 10     // Note: no 2nd param supplied.     // sumX is a new function generated from partially applied sumVals.     // ie "sumX is a partial application of sumVals." let sum = sumX 20     // Invokes sumX, passing in expected int (parameter y from original)  val sumVals : int -> int -> int val sumX : (int -> int) val sum : int = 30 RealFunctionsToVectorFunction and RealFunctionsToFastVectorFunction helper methods - combines an array of delegates returning a real number or a vector into vector or matrix functions. The resulting vector function returns a vector whose components are the function values of the delegates in the array. var funcVector = FunctionFactory.RealFunctionsToVectorFunction(     new MultivariateRealFunction(myFunc1),     new MultivariateRealFunction(myFunc2));  The IterativeAlgorithm<T> abstract base class Iterative algorithms are common in numerical computing - a method is executed repeatedly until a certain condition is reached, approximating the result of a calculation with increasing accuracy until a certain threshold is reached. If the desired accuracy is achieved, the algorithm is said to converge. This base class is derived by many classes in the Extreme.Mathematics.EquationSolvers and Extreme.Mathematics.Optimization namespaces, as well as the ManagedIterativeAlgorithm class which contains a driver method that manages the iteration process.  The ConvergenceTest abstract base class This class is used to specify algorithm Termination , convergence and results - calculates an estimate for the error, and signals termination of the algorithm when the error is below a specified tolerance. Termination Criteria - specify the success condition as the difference between some quantity and its actual value is within a certain tolerance – 2 ways: absolute error - difference between the result and the actual value. relative error is the difference between the result and the actual value relative to the size of the result. Tolerance property - specify trade-off between accuracy and execution time. The lower the tolerance, the longer it will take for the algorithm to obtain a result within that tolerance. Most algorithms in the EO NumLib have a default value of MachineConstants.SqrtEpsilon - gives slightly less than 8 digits of accuracy. ConvergenceCriterion property - specify under what condition the algorithm is assumed to converge. Using the ConvergenceCriterion enum: WithinAbsoluteTolerance / WithinRelativeTolerance / WithinAnyTolerance / NumberOfIterations Active property - selectively ignore certain convergence tests Error property - returns the estimated error after a run MaxIterations / MaxEvaluations properties - Other Termination Criteria - If the algorithm cannot achieve the desired accuracy, the algorithm still has to end – according to an absolute boundary. Status property - indicates how the algorithm terminated - the AlgorithmStatus enum values:NoResult / Busy / Converged (ended normally - The desired accuracy has been achieved) / IterationLimitExceeded / EvaluationLimitExceeded / RoundOffError / BadFunction / Divergent / ConvergedToFalseSolution. After the iteration terminates, the Status should be inspected to verify that the algorithm terminated normally. Alternatively, you can set the ThrowExceptionOnFailure to true. Result property - returns the result of the algorithm. This property contains the best available estimate, even if the desired accuracy was not obtained. IterationsNeeded / EvaluationsNeeded properties - returns the number of iterations required to obtain the result, number of function evaluations.  Concrete Types of Convergence Test classes SimpleConvergenceTest class - test if a value is close to zero or very small compared to another value. VectorConvergenceTest class - test convergence of vectors. This class has two additional properties. The Norm property specifies which norm is to be used when calculating the size of the vector - the VectorConvergenceNorm enum values: EuclidianNorm / Maximum / SumOfAbsoluteValues. The ErrorMeasure property specifies how the error is to be measured – VectorConvergenceErrorMeasure enum values: Norm / Componentwise ConvergenceTestCollection class - represent a combination of tests. The Quantifier property is a ConvergenceTestQuantifier enum that specifies how the tests in the collection are to be combined: Any / All  The AlgorithmHelper Class inherits from IterativeAlgorithm<T> and exposes two methods for convergence testing. IsValueWithinTolerance<T> method - determines whether a value is close to another value to within an algorithm's requested tolerance. IsIntervalWithinTolerance<T> method - determines whether an interval is within an algorithm's requested tolerance.

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• Collision Error

  - by Manji

  I am having trouble with collision detection part of the game. I am using touch events to fire the gun as you will see in the video. Note, the android icon is a temporary graphic for the bullets When ever the user touches (represented by clicks in the video)the bullet appears and kills random sprites. As you can see it never touches the sprites it kills or kill the sprites it does touch. My Question is How do I fix it, so that the sprite dies when the bullet hits it? Collision Code snippet: //Handles Collision private void CheckCollisions(){ synchronized(mSurfaceHolder){ for (int i = sprites.size() - 1; i >= 0; i--){ Sprite sprite = sprites.get(i); if(sprite.isCollision(bullet)){ sprites.remove(sprite); mScore++; if(sprites.size() == 0){ mLevel = mLevel +1; currentLevel++; initLevel(); } break; } } } } Sprite Class Code Snippet: //bounding box left<right and top>bottom int left ; int right ; int top ; int bottom ; public boolean isCollision(Beam other) { // TODO Auto-generated method stub if(this.left>other.right || other.left<other.right)return false; if(this.bottom>other.top || other.bottom<other.top)return false; return true; } EDIT 1: Sprite Class: public class Sprite { // direction = 0 up, 1 left, 2 down, 3 right, // animation = 3 back, 1 left, 0 front, 2 right int[] DIRECTION_TO_ANIMATION_MAP = { 3, 1, 0, 2 }; private static final int BMP_ROWS = 4; private static final int BMP_COLUMNS = 3; private static final int MAX_SPEED = 5; private HitmanView gameView; private Bitmap bmp; private int x; private int y; private int xSpeed; private int ySpeed; private int currentFrame = 0; private int width; private int height; //bounding box left<right and top>bottom int left ; int right ; int top ; int bottom ; public Sprite(HitmanView gameView, Bitmap bmp) { this.width = bmp.getWidth() / BMP_COLUMNS; this.height = bmp.getHeight() / BMP_ROWS; this.gameView = gameView; this.bmp = bmp; Random rnd = new Random(); x = rnd.nextInt(gameView.getWidth() - width); y = rnd.nextInt(gameView.getHeight() - height); xSpeed = rnd.nextInt(MAX_SPEED * 2) - MAX_SPEED; ySpeed = rnd.nextInt(MAX_SPEED * 2) - MAX_SPEED; } private void update() { if (x >= gameView.getWidth() - width - xSpeed || x + xSpeed <= 0) { xSpeed = -xSpeed; } x = x + xSpeed; if (y >= gameView.getHeight() - height - ySpeed || y + ySpeed <= 0) { ySpeed = -ySpeed; } y = y + ySpeed; currentFrame = ++currentFrame % BMP_COLUMNS; } public void onDraw(Canvas canvas) { update(); int srcX = currentFrame * width; int srcY = getAnimationRow() * height; Rect src = new Rect(srcX, srcY, srcX + width, srcY + height); Rect dst = new Rect(x, y, x + width, y + height); canvas.drawBitmap(bmp, src, dst, null); } private int getAnimationRow() { double dirDouble = (Math.atan2(xSpeed, ySpeed) / (Math.PI / 2) + 2); int direction = (int) Math.round(dirDouble) % BMP_ROWS; return DIRECTION_TO_ANIMATION_MAP[direction]; } public boolean isCollision(float x2, float y2){ return x2 > x && x2 < x + width && y2 > y && y2 < y + height; } public boolean isCollision(Beam other) { // TODO Auto-generated method stub if(this.left>other.right || other.left<other.right)return false; if(this.bottom>other.top || other.bottom<other.top)return false; return true; } } Bullet Class: public class Bullet { int mX; int mY; private Bitmap mBitmap; //bounding box left<right and top>bottom int left ; int right ; int top ; int bottom ; public Bullet (Bitmap mBitmap){ this.mBitmap = mBitmap; } public void draw(Canvas canvas, int mX, int mY) { this.mX = mX; this.mY = mY; canvas.drawBitmap(mBitmap, mX, mY, null); } }

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• Collision Detection problems in Voxel Engine (XNA)

  - by Darestium

  I am creating a minecraft like terrain engine in XNA and have had some collision problems for quite some time. I have checked and changed my code based on other peoples collision code and I still have the same problem. It always seems to be off by about a block. for instance, if I walk across a bridge which is one block high I fall through it. Also, if you walk towards a "row" of blocks like this: You are able to stand "inside" the left most one, and you collide with nothing in the right most side (where there is no block and is not visible on this image). Here is all my collision code: private void Move(GameTime gameTime, Vector3 direction) { float speed = playermovespeed * (float)gameTime.ElapsedGameTime.TotalSeconds; Matrix rotationMatrix = Matrix.CreateRotationY(player.Camera.LeftRightRotation); Vector3 rotatedVector = Vector3.Transform(direction, rotationMatrix); rotatedVector.Normalize(); Vector3 testVector = rotatedVector; testVector.Normalize(); Vector3 movePosition = player.position + testVector * speed; Vector3 midBodyPoint = movePosition + new Vector3(0, -0.7f, 0); Vector3 headPosition = movePosition + new Vector3(0, 0.1f, 0); if (!world.GetBlock(movePosition).IsSolid && !world.GetBlock(midBodyPoint).IsSolid && !world.GetBlock(headPosition).IsSolid) { player.position += rotatedVector * speed; } //player.position += rotatedVector * speed; } ... public void UpdatePosition(GameTime gameTime) { player.velocity.Y += playergravity * (float)gameTime.ElapsedGameTime.TotalSeconds; Vector3 footPosition = player.Position + new Vector3(0f, -1.5f, 0f); Vector3 headPosition = player.Position + new Vector3(0f, 0.1f, 0f); // If the block below the player is solid the Y velocity should be zero if (world.GetBlock(footPosition).IsSolid || world.GetBlock(headPosition).IsSolid) { player.velocity.Y = 0; } UpdateJump(gameTime); UpdateCounter(gameTime); ProcessInput(gameTime); player.Position = player.Position + player.velocity * (float)gameTime.ElapsedGameTime.TotalSeconds; velocity = Vector3.Zero; } and the one and only function in the camera class: protected void CalculateView() { Matrix rotationMatrix = Matrix.CreateRotationX(upDownRotation) * Matrix.CreateRotationY(leftRightRotation); lookVector = Vector3.Transform(Vector3.Forward, rotationMatrix); cameraFinalTarget = Position + lookVector; Vector3 cameraRotatedUpVector = Vector3.Transform(Vector3.Up, rotationMatrix); viewMatrix = Matrix.CreateLookAt(Position, cameraFinalTarget, cameraRotatedUpVector); } which is called when the rotation variables are changed: public float LeftRightRotation { get { return leftRightRotation; } set { leftRightRotation = value; CalculateView(); } } public float UpDownRotation { get { return upDownRotation; } set { upDownRotation = value; CalculateView(); } } World class: public Block GetBlock(int x, int y, int z) { if (InBounds(x, y, z)) { Vector3i regionalPosition = GetRegionalPosition(x, y, z); Vector3i region = GetRegionPosition(x, y, z); return regions[region.X, region.Y, region.Z].Blocks[regionalPosition.X, regionalPosition.Y, regionalPosition.Z]; } return new Block(BlockType.none); } public Vector3i GetRegionPosition(int x, int y, int z) { int regionx = x == 0 ? 0 : x / Variables.REGION_SIZE_X; int regiony = y == 0 ? 0 : y / Variables.REGION_SIZE_Y; int regionz = z == 0 ? 0 : z / Variables.REGION_SIZE_Z; return new Vector3i(regionx, regiony, regionz); } public Vector3i GetRegionalPosition(int x, int y, int z) { int regionx = x == 0 ? 0 : x / Variables.REGION_SIZE_X; int X = x % Variables.REGION_SIZE_X; int regiony = y == 0 ? 0 : y / Variables.REGION_SIZE_Y; int Y = y % Variables.REGION_SIZE_Y; int regionz = z == 0 ? 0 : z / Variables.REGION_SIZE_Z; int Z = z % Variables.REGION_SIZE_Z; return new Vector3i(X, Y, Z); } Any ideas how to fix this problem? EDIT 1: Graphic of the problem: EDIT 2 GetBlock, Vector3 version: public Block GetBlock(Vector3 position) { int x = (int)Math.Floor(position.X); int y = (int)Math.Floor(position.Y); int z = (int)Math.Ceiling(position.Z); Block block = GetBlock(x, y, z); return block; } Now, the thing is I tested the theroy that the Z is always "off by one" and by ceiling the value it actually works as intended. Altough it still could be greatly more accurate (when you go down holes you can see through the sides, and I doubt it will work with negitive positions). I also does not feel clean Flooring the X and Y values and just Ceiling the Z. I am surely not doing something correctly still.

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• University teaches DOS-style C++, how to deal with it

  - by gaidal

  Half a year ago I had a look at available programming educations. I chose this one because unlike most of the choices: The majority of the courses seemed to be about something concrete and useful; the languages used are C++ and Java which are platform-independent; later courses include developing for mobile devices and a course on Android development, which seemed modern and relevant. Now after two introductory courses we're just starting with C++, and my programming professor seems a bit weird. He's tested us on things like "why should you use constants" and "why are globals bad" in a kind of mechanical way, without much context, before teaching actual programming. His handouts use system("pause"), system("cls"), and getch() from some conio.h that seems ancient according to what I've read. I just did a task that was about printing the "ASCII letters from 32 to 255" (huh?), with an example picture showing a table with Windows' Extended ASCII - of course I got other results for 128-255 on my Arch Linux that uses Unicode, and this isn't mentioned at all. I don't know, it just doesn't seem right... As if he is teaching programming because he has to, perhaps? Should I bring such things up? Hmm. I was looking forward to learning from someone who really knows stuff, and in an academic, rigorous way, like SICP or something. Aren't professors in programming supposed to be like that? I studied math for a while and every teacher and assistant there were really precise about what they said, but this is my second programming teacher that is sort of disappointing. Oh well. Now, question: Is this what to expect from universities or Not OK, and how do I deal with it? I have never touched the language C++ (or C) until now, and am not the right person to jump up and say "This is So Wrong!", so if I google something and find 10 people who say "xxx is blasphemy", how do I skillfully communicate this? I do think it would be better for those classmates who are total beginners not to learn bad habits (such as these vibes of total ignorance of other platforms!) during the upcoming courses, but don't want to disrespect the teacher. I don't know if it's reasonable or just cocky to bring up things like "what about other platforms?" or "but what about this article or stackoverflow answer that I read that said..." for every assignment? Or, if he keeps ignoring non-Windows-programming, should I give up and focus on my own projects or somehow argue that this really isn't OK nowadays? Are there any programming teachers out there, what do you think? By the way these are web-based courses, all interaction between teachers and students takes place in a forum. EDIT: A few answers seem to be making some incorrect assumptions, so maybe I should add a few things. I have been doing programming for fun on and off for 10 years, am pretty comfortable in 3 languages and read programming blogs et c regularly. Also, I feel kind of done being a student, having a degree in another field. I just need another, relevant diploma to work as a programmer, so I'm going back for that. Studying computer science for 5 years is not for me anymore, even though I enjoy learning and solving problems in my free time. Second, let me highlight that I don't expect it to be like the industry at all, quite the contrary. I expect it to be academic, dry and unnecessarily correct. No, it's not just math. Every professor I have had in math, or Japanese (major) or Chinese (minor) have been very very academic, discussing subtle points for hours with passion. But the courses I'm taking now and a previous one in programming don't seem serious. They neither resemble industry NOR academia. That is the problem. And it's not because I can't learn programming anyway. Third, I don't necessarily want to learn C++ or Android development, and I know I could teach myself those and anything else if I wanted to. But I am going back to school anyway, and those platform-independent languages and mobile stuff made me think that maybe they're serious about teaching something relevant here. Seems like I got this wrong, but we'll see.

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• opengl problem works on droid but not droid eris and others.

  - by nathan

  This GlRenderer works fine on the moto droid, but does not work well at all on droid eris or other android phones does anyone know why? package com.ntu.way2fungames.spacehockeybase; import java.io.DataInputStream; import java.io.IOException; import java.nio.Buffer; import java.nio.FloatBuffer; import javax.microedition.khronos.egl.EGLConfig; import javax.microedition.khronos.opengles.GL10; import com.ntu.way2fungames.LoadFloatArray; import com.ntu.way2fungames.OGLTriReader; import android.content.res.AssetManager; import android.content.res.Resources; import android.opengl.GLU; import android.opengl.GLSurfaceView.Renderer; import android.os.Handler; import android.os.Message; public class GlRenderer extends Thread implements Renderer { private float drawArray[]; private float yoff; private float yoff2; private long lastRenderTime; private float[] yoffs= new float[10]; int Width; int Height; private float[] pixelVerts = new float[] { +.0f,+.0f,2, +.5f,+.5f,0, +.5f,-.5f,0, +.0f,+.0f,2, +.5f,-.5f,0, -.5f,-.5f,0, +.0f,+.0f,2, -.5f,-.5f,0, -.5f,+.5f,0, +.0f,+.0f,2, -.5f,+.5f,0, +.5f,+.5f,0, }; @Override public void run() { } private float[] arenaWalls = new float[] { 8.00f,2.00f,1f,2f,2f,1f,2.00f,8.00f,1f,8.00f,2.00f,1f,2.00f,8.00f,1f,8.00f,8.00f,1f, 2.00f,8.00f,1f,2f,2f,1f,0.00f,0.00f,0f,2.00f,8.00f,1f,0.00f,0.00f,0f,0.00f,10.00f,0f, 8.00f,8.00f,1f,2.00f,8.00f,1f,0.00f,10.00f,0f,8.00f,8.00f,1f,0.00f,10.00f,0f,10.00f,10.00f,0f, 2f,2f,1f,8.00f,2.00f,1f,10.00f,0.00f,0f,2f,2f,1f,10.00f,0.00f,0f,0.00f,0.00f,0f, 8.00f,2.00f,1f,8.00f,8.00f,1f,10.00f,10.00f,0f,8.00f,2.00f,1f,10.00f,10.00f,0f,10.00f,0.00f,0f, 10.00f,10.00f,0f,0.00f,10.00f,0f,0.00f,0.00f,0f,10.00f,10.00f,0f,0.00f,0.00f,0f,10.00f,0.00f,0f, 8.00f,6.00f,1f,8.00f,4.00f,1f,122f,4.00f,1f,8.00f,6.00f,1f,122f,4.00f,1f,122f,6.00f,1f, 8.00f,6.00f,1f,122f,6.00f,1f,120f,7.00f,0f,8.00f,6.00f,1f,120f,7.00f,0f,10.00f,7.00f,0f, 122f,4.00f,1f,8.00f,4.00f,1f,10.00f,3.00f,0f,122f,4.00f,1f,10.00f,3.00f,0f,120f,3.00f,0f, 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350f,0.00f,0f,360f,0.00f,0f,360f,10.00f,0f,350f,0.00f,0f,360f,10.00f,0f,350f,10.00f,0f, 358f,6.00f,1f,472f,6.00f,1f,470f,7.00f,0f,358f,6.00f,1f,470f,7.00f,0f,360f,7.00f,0f, 472f,4.00f,1f,358f,4.00f,1f,360f,3.00f,0f,472f,4.00f,1f,360f,3.00f,0f,470f,3.00f,0f, 472f,4.00f,1f,472f,6.00f,1f,358f,6.00f,1f,472f,4.00f,1f,358f,6.00f,1f,358f,4.00f,1f, 472f,848f,1f,472f,850f,1f,358f,850f,1f,472f,848f,1f,358f,850f,1f,358f,848f,1f, 472f,848f,1f,358f,848f,1f,360f,847f,0f,472f,848f,1f,360f,847f,0f,470f,847f,0f, 358f,850f,1f,472f,850f,1f,470f,851f,0f,358f,850f,1f,470f,851f,0f,360f,851f,0f, 350f,844f,0f,360f,844f,0f,360f,854f,0f,350f,844f,0f,360f,854f,0f,350f,854f,0f, 352f,852f,1f,352f,846f,1f,350f,844f,0f,352f,852f,1f,350f,844f,0f,350f,854f,0f, 358f,852f,1f,352f,852f,1f,350f,854f,0f,358f,852f,1f,350f,854f,0f,360f,854f,0f, 352f,846f,1f,358f,846f,1f,360f,844f,0f,352f,846f,1f,360f,844f,0f,350f,844f,0f, 358f,846f,1f,358f,852f,1f,360f,854f,0f,358f,846f,1f,360f,854f,0f,360f,844f,0f, 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350f,844f,0f,350f,854f,0f,345.45f,836.34f,-0.50f,350f,844f,0f,345.45f,836.34f,-0.50f,345.45f,826.76f,-0.50f, 360f,847f,0f,470f,847f,0f,460.49f,829.63f,-0.50f,360f,847f,0f,460.49f,829.63f,-0.50f,355.04f,829.63f,-0.50f, 470f,7.00f,0f,360f,7.00f,0f,355.04f,24.37f,-0.50f,470f,7.00f,0f,355.04f,24.37f,-0.50f,460.49f,24.37f,-0.50f, 350f,10.00f,0f,350f,0.00f,0f,345.45f,17.66f,-0.50f,350f,10.00f,0f,345.45f,17.66f,-0.50f,345.45f,27.24f,-0.50f, 130f,10.00f,0f,130f,0.00f,0f,134.55f,17.66f,-0.50f,130f,10.00f,0f,134.55f,17.66f,-0.50f,134.55f,27.24f,-0.50f, 473f,844f,0f,473f,10f,0f,463.36f,27.24f,-0.50f,473f,844f,0f,463.36f,27.24f,-0.50f,463.36f,826.76f,-0.50f, 7f,10f,0f,7f,844f,0f,16.64f,826.76f,-0.50f,7f,10f,0f,16.64f,826.76f,-0.50f,16.64f,27.24f,-0.50f, 120f,7.00f,0f,10.00f,7.00f,0f,19.51f,24.37f,-0.50f,120f,7.00f,0f,19.51f,24.37f,-0.50f,124.96f,24.37f,-0.50f, 120f,7.00f,0f,130f,10.00f,0f,134.55f,27.24f,-0.50f,120f,7.00f,0f,134.55f,27.24f,-0.50f,124.96f,24.37f,-0.50f, 10.00f,7.00f,0f,7f,10f,0f,16.64f,27.24f,-0.50f,10.00f,7.00f,0f,16.64f,27.24f,-0.50f,19.51f,24.37f,-0.50f, 350f,10.00f,0f,360f,7.00f,0f,355.04f,24.37f,-0.50f,350f,10.00f,0f,355.04f,24.37f,-0.50f,345.45f,27.24f,-0.50f, 473f,10f,0f,470f,7.00f,0f,460.49f,24.37f,-0.50f,473f,10f,0f,460.49f,24.37f,-0.50f,463.36f,27.24f,-0.50f, 473f,844f,0f,470f,847f,0f,460.49f,829.63f,-0.50f,473f,844f,0f,460.49f,829.63f,-0.50f,463.36f,826.76f,-0.50f, 360f,847f,0f,350f,844f,0f,345.45f,826.76f,-0.50f,360f,847f,0f,345.45f,826.76f,-0.50f,355.04f,829.63f,-0.50f, 130f,844f,0f,120f,847f,0f,124.96f,829.63f,-0.50f,130f,844f,0f,124.96f,829.63f,-0.50f,134.55f,826.76f,-0.50f, 7f,844f,0f,10f,847f,0f,19.51f,829.63f,-0.50f,7f,844f,0f,19.51f,829.63f,-0.50f,16.64f,826.76f,-0.50f, 19.51f,829.63f,-0.50f,124.96f,829.63f,-0.50f,136.47f,789.37f,-2f,19.51f,829.63f,-0.50f,136.47f,789.37f,-2f,41.56f,789.37f,-2f, 134.55f,826.76f,-0.50f,134.55f,836.34f,-0.50f,145.09f,795.41f,-2f,134.55f,826.76f,-0.50f,145.09f,795.41f,-2f,145.09f,786.78f,-2f, 345.45f,826.76f,-0.50f,345.45f,836.34f,-0.50f,334.91f,795.41f,-2f,345.45f,826.76f,-0.50f,334.91f,795.41f,-2f,334.91f,786.78f,-2f, 355.04f,829.63f,-0.50f,460.49f,829.63f,-0.50f,438.44f,789.37f,-2f,355.04f,829.63f,-0.50f,438.44f,789.37f,-2f,343.53f,789.37f,-2f, 460.49f,24.37f,-0.50f,355.04f,24.37f,-0.50f,343.53f,64.63f,-2f,460.49f,24.37f,-0.50f,343.53f,64.63f,-2f,438.44f,64.63f,-2f, 345.45f,27.24f,-0.50f,345.45f,17.66f,-0.50f,334.91f,58.59f,-2f,345.45f,27.24f,-0.50f,334.91f,58.59f,-2f,334.91f,67.22f,-2f, 134.55f,27.24f,-0.50f,134.55f,17.66f,-0.50f,145.09f,58.59f,-2f,134.55f,27.24f,-0.50f,145.09f,58.59f,-2f,145.09f,67.22f,-2f, 463.36f,826.76f,-0.50f,463.36f,27.24f,-0.50f,441.03f,67.22f,-2f,463.36f,826.76f,-0.50f,441.03f,67.22f,-2f,441.03f,786.78f,-2f, 16.64f,27.24f,-0.50f,16.64f,826.76f,-0.50f,38.97f,786.78f,-2f,16.64f,27.24f,-0.50f,38.97f,786.78f,-2f,38.97f,67.22f,-2f, 124.96f,24.37f,-0.50f,19.51f,24.37f,-0.50f,41.56f,64.63f,-2f,124.96f,24.37f,-0.50f,41.56f,64.63f,-2f,136.47f,64.63f,-2f, 124.96f,24.37f,-0.50f,134.55f,27.24f,-0.50f,145.09f,67.22f,-2f,124.96f,24.37f,-0.50f,145.09f,67.22f,-2f,136.47f,64.63f,-2f, 19.51f,24.37f,-0.50f,16.64f,27.24f,-0.50f,38.97f,67.22f,-2f,19.51f,24.37f,-0.50f,38.97f,67.22f,-2f,41.56f,64.63f,-2f, 345.45f,27.24f,-0.50f,355.04f,24.37f,-0.50f,343.53f,64.63f,-2f,345.45f,27.24f,-0.50f,343.53f,64.63f,-2f,334.91f,67.22f,-2f, 463.36f,27.24f,-0.50f,460.49f,24.37f,-0.50f,438.44f,64.63f,-2f,463.36f,27.24f,-0.50f,438.44f,64.63f,-2f,441.03f,67.22f,-2f, 463.36f,826.76f,-0.50f,460.49f,829.63f,-0.50f,438.44f,789.37f,-2f,463.36f,826.76f,-0.50f,438.44f,789.37f,-2f,441.03f,786.78f,-2f, 355.04f,829.63f,-0.50f,345.45f,826.76f,-0.50f,334.91f,786.78f,-2f,355.04f,829.63f,-0.50f,334.91f,786.78f,-2f,343.53f,789.37f,-2f, 134.55f,826.76f,-0.50f,124.96f,829.63f,-0.50f,136.47f,789.37f,-2f,134.55f,826.76f,-0.50f,136.47f,789.37f,-2f,145.09f,786.78f,-2f, 16.64f,826.76f,-0.50f,19.51f,829.63f,-0.50f,41.56f,789.37f,-2f,16.64f,826.76f,-0.50f,41.56f,789.37f,-2f,38.97f,786.78f,-2f, }; private float[] backgroundData = new float[] { // # ,Scale, Speed, 300 , 1.05f, .001f, 150 , 1.07f, .002f, 075 , 1.10f, .003f, 040 , 1.12f, .006f, 20 , 1.15f, .012f, 10 , 1.25f, .025f, 05 , 1.50f, .050f, 3 , 2.00f, .100f, 2 , 3.00f, .200f, }; private float[] triangleCoords = new float[] { 0, -25, 0, -.75f, -1, 0, +.75f, -1, 0, 0, +2, 0, -.99f, -1, 0, .99f, -1, 0, }; private float[] triangleColors = new float[] { 1.0f, 1.0f, 1.0f, 0.05f, 1.0f, 1.0f, 1.0f, 0.5f, 1.0f, 1.0f, 1.0f, 0.5f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 0.5f, 1.0f, 1.0f, 1.0f, 0.5f, }; private float[] drawArray2; private FloatBuffer drawBuffer2; private float[] colorArray2; private static FloatBuffer colorBuffer; private static FloatBuffer triangleBuffer; private static FloatBuffer quadBuffer; private static FloatBuffer drawBuffer; private float[] backgroundVerts; private FloatBuffer backgroundVertsWrapped; private float[] backgroundColors; private Buffer backgroundColorsWraped; private FloatBuffer backgroundColorsWrapped; private FloatBuffer arenaWallsWrapped; private FloatBuffer arenaColorsWrapped; private FloatBuffer arena2VertsWrapped; private FloatBuffer arena2ColorsWrapped; private long wallHitStartTime; private int wallHitDrawTime; private FloatBuffer pixelVertsWrapped; private float[] wallHit; private FloatBuffer pixelColorsWrapped; //private float[] pitVerts; private Resources lResources; private FloatBuffer pitVertsWrapped; private FloatBuffer pitColorsWrapped; private boolean arena2; private long lastStartTime; private long startTime; private int state=1; private long introEndTime; protected long introTotalTime =8000; protected long introStartTime; private boolean initDone= false; private static int stateIntro = 0; private static int stateGame = 1; public GlRenderer(spacehockey nspacehockey) { lResources = nspacehockey.getResources(); nspacehockey.SetHandlerToGLRenderer(new Handler() { @Override public void handleMessage(Message m) { if (m.what ==0){ wallHit = m.getData().getFloatArray("wall hit"); wallHitStartTime =System.currentTimeMillis(); wallHitDrawTime = 1000; }else if (m.what ==1){ //state = stateIntro; introEndTime= System.currentTimeMillis()+introTotalTime ; introStartTime = System.currentTimeMillis(); } }}); } public void onSurfaceCreated(GL10 gl, EGLConfig config) { gl.glShadeModel(GL10.GL_SMOOTH); gl.glClearColor(.01f, .01f, .01f, .1f); gl.glClearDepthf(1.0f); gl.glEnable(GL10.GL_DEPTH_TEST); gl.glDepthFunc(GL10.GL_LEQUAL); gl.glHint(GL10.GL_PERSPECTIVE_CORRECTION_HINT, GL10.GL_NICEST); } private float SumOfStrideI(float[] data, int offset, int stride) { int sum= 0; for (int i=offset;i<data.length-1;i=i+stride){ sum = (int) (data[i]+sum); } return sum; } public void onDrawFrame(GL10 gl) { if (state== stateIntro){DrawIntro(gl);} if (state== stateGame){DrawGame(gl);} } private void DrawIntro(GL10 gl) { startTime = System.currentTimeMillis(); if (startTime< introEndTime){ float ptd = (float)(startTime- introStartTime)/(float)introTotalTime; float ptl = 1-ptd; gl.glClear(GL10.GL_COLOR_BUFFER_BIT);//dont move gl.glMatrixMode(GL10.GL_MODELVIEW); int setVertOff = 0; gl.glEnableClientState(GL10.GL_VERTEX_ARRAY); gl.glEnableClientState(GL10.GL_COLOR_ARRAY); gl.glColorPointer(4, GL10.GL_FLOAT, 0, backgroundColorsWrapped); for (int i = 0; i < backgroundData.length / 3; i = i + 1) { int setoff = i * 3; int setVertLen = (int) backgroundData[setoff]; yoffs[i] = (backgroundData[setoff + 2]*(90+(ptl*250))) + yoffs[i]; if (yoffs[i] > Height) {yoffs[i] = 0;} gl.glPushMatrix(); //gl.glTranslatef(0, -(Height/2), 0); //gl.glScalef(1f, 1f+(ptl*2), 1f); //gl.glTranslatef(0, +(Height/2), 0); gl.glTranslatef(0, yoffs[i], i+60); gl.glVertexPointer(3, GL10.GL_FLOAT, 0, backgroundVertsWrapped); gl.glDrawArrays(GL10.GL_TRIANGLES, (setVertOff * 2 * 3) - 0, (setVertLen * 2 * 3) - 1); gl.glTranslatef(0, -Height, 0); gl.glDrawArrays(GL10.GL_TRIANGLES, (setVertOff * 2 * 3) - 0, (setVertLen * 2 * 3) - 1); setVertOff = (int) (setVertOff + setVertLen); gl.glPopMatrix(); } gl.glDisableClientState(GL10.GL_VERTEX_ARRAY); gl.glDisableClientState(GL10.GL_COLOR_ARRAY); }else{state = stateGame;} } private void DrawGame(GL10 gl) { lastStartTime = startTime; startTime = System.currentTimeMillis(); long moveTime = startTime-lastStartTime; gl.glClear(GL10.GL_COLOR_BUFFER_BIT);//dont move gl.glMatrixMode(GL10.GL_MODELVIEW); int setVertOff = 0; gl.glEnableClientState(GL10.GL_VERTEX_ARRAY); gl.glEnableClientState(GL10.GL_COLOR_ARRAY); gl.glColorPointer(4, GL10.GL_FLOAT, 0, backgroundColorsWrapped); for (int i = 0; i < backgroundData.length / 3; i = i + 1) { int setoff = i * 3; int setVertLen = (int) backgroundData[setoff]; yoffs[i] = (backgroundData[setoff + 2]*moveTime) + yoffs[i]; if (yoffs[i] > Height) {yoffs[i] = 0;} gl.glPushMatrix(); gl.glTranslatef(0, yoffs[i], i+60); gl.glVertexPointer(3, GL10.GL_FLOAT, 0, backgroundVertsWrapped); gl.glDrawArrays(GL10.GL_TRIANGLES, (setVertOff * 6) - 0, (setVertLen *6) - 1); gl.glTranslatef(0, -Height, 0); gl.glDrawArrays(GL10.GL_TRIANGLES, (setVertOff * 6) - 0, (setVertLen *6) - 1); setVertOff = (int) (setVertOff + setVertLen); gl.glPopMatrix(); } //arena frame gl.glPushMatrix(); gl.glVertexPointer(3, GL10.GL_FLOAT, 0, arenaWallsWrapped); gl.glColorPointer(4, GL10.GL_FLOAT, 0, arenaColorsWrapped); gl.glColor4f(.1f, .5f, 1f, 1f); gl.glTranslatef(0, 0, 50); gl.glDrawArrays(GL10.GL_TRIANGLES, 0, (int)(arenaWalls.length / 3)); gl.glPopMatrix(); //arena2 frame if (arena2 == true){ gl.glLoadIdentity(); gl.glVertexPointer(3, GL10.GL_FLOAT, 0, pitVertsWrapped); gl.glColorPointer(4, GL10.GL_FLOAT, 0, pitColorsWrapped); gl.glTranslatef(0, -Height, 40); gl.glDrawArrays(GL10.GL_TRIANGLES, 0, (int)(pitVertsWrapped.capacity() / 3)); } if (wallHitStartTime != 0) { float timeRemaining = (wallHitStartTime + wallHitDrawTime)-System.currentTimeMillis(); if (timeRemaining>0) { gl.glPushMatrix(); float percentDone = 1-(timeRemaining/wallHitDrawTime); gl.glLoadIdentity(); gl.glVertexPointer(3, GL10.GL_FLOAT, 0, pixelVertsWrapped); gl.glColorPointer(4, GL10.GL_FLOAT, 0, pixelColorsWrapped); gl.glTranslatef(wallHit[0], wallHit[1], 0); gl.glScalef(8, Height*percentDone, 0); gl.glDrawArrays(GL10.GL_TRIANGLES, 0, 12); gl.glPopMatrix(); } else { wallHitStartTime = 0; } } gl.glDisableClientState(GL10.GL_VERTEX_ARRAY); gl.glDisableClientState(GL10.GL_COLOR_ARRAY); } public void init(GL10 gl) { if (arena2 == true) { AssetManager assetManager = lResources.getAssets(); try { // byte[] ba = {111,111}; DataInputStream Dis = new DataInputStream(assetManager .open("arena2.ogl")); pitVertsWrapped = LoadFloatArray.FromDataInputStream(Dis); pitColorsWrapped = MakeFakeLighting(pitVertsWrapped.array(), .25f, .50f, 1f, 200, .5f); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } if ((Height != 854) || (Width != 480)) { arenaWalls = ScaleFloats(arenaWalls, Width / 480f, Height / 854f); } arenaWallsWrapped = FloatBuffer.wrap(arenaWalls); arenaColorsWrapped = MakeFakeLighting(arenaWalls, .03f, .16f, .33f, .33f, 3); pixelVertsWrapped = FloatBuffer.wrap(pixelVerts); pixelColorsWrapped = MakeFakeLighting(pixelVerts, .03f, .16f, .33f, .10f, 20); initDone=true; } public void onSurfaceChanged(GL10 gl, int nwidth, int nheight) { Width= nwidth; Height = nheight; // avoid division by zero if (Height == 0) Height = 1; // draw on the entire screen gl.glViewport(0, 0, Width, Height); // setup projection matrix gl.glMatrixMode(GL10.GL_PROJECTION); gl.glLoadIdentity(); gl.glOrthof(0, Width, Height, 0, 100, -100); // gl.glOrthof(-nwidth*2, nwidth*2, nheight*2,-nheight*2, 100, -100); // GLU.gluPerspective(gl, 180.0f, (float)nwidth / (float)nheight, // 1000.0f, -1000.0f); gl.glEnable(GL10.GL_BLEND); gl.glBlendFunc(GL10.GL_SRC_ALPHA, GL10.GL_ONE_MINUS_SRC_ALPHA); System.gc(); if (initDone == false){ SetupStars(); init(gl); } } public void SetupStars(){ backgroundVerts = new float[(int) SumOfStrideI(backgroundData,0,3)*triangleCoords.length]; backgroundColors = new float[(int) SumOfStrideI(backgroundData,0,3)*triangleColors.length]; int iii=0; int vc=0; float ascale=1; for (int i=0;i<backgroundColors.length-1;i=i+1){ if (iii==0){ascale = (float) Math.random();} if (vc==3){ backgroundColors[i]= (float) (triangleColors[iii]*(ascale)); }else if(vc==2){ backgroundColors[i]= (float) (triangleColors[iii]-(Math.random()*.2)); }else{ backgroundColors[i]= (float) (triangleColors[iii]-(Math.random()*.3)); } iii=iii+1;if (iii> triangleColors.length-1){iii=0;} vc=vc+1; if (vc>3){vc=0;} } int ii=0; int i =0; int set =0; while(ii<backgroundVerts.length-1){ float scale = (float) backgroundData[(set*3)+1]; int length= (int) backgroundData[(set*3)]; for (i=0;i<length;i=i+1){ if (set ==0){ AddVertsToArray(ScaleFloats(triangleCoords, scale,scale*.25f), backgroundVerts, (float)(Math.random()*Width),(float) (Math.random()*Height), ii); }else{ AddVertsToArray(ScaleFloats(triangleCoords, scale), backgroundVerts, (float)(Math.random()*Width),(float) (Math.random()*Height), ii);} ii=ii+triangleCoords.length; } set=set+1; } backgroundVertsWrapped = FloatBuffer.wrap(backgroundVerts); backgroundColorsWrapped = FloatBuffer.wrap(backgroundColors); } public void AddVertsToArray(float[] sva,float[]dva,float ox,float oy,int start){ //x for (int i=0;i<sva.length;i=i+3){ if((start+i)<dva.length){dva[start+i]= sva[i]+ox;} } //y for (int i=1;i<sva.length;i=i+3){ if((start+i)<dva.length){dva[start+i]= sva[i]+oy;} } //z for (int i=2;i<sva.length;i=i+3){ if((start+i)<dva.length){dva[start+i]= sva[i];} } } public FloatBuffer MakeFakeLighting(float[] sa,float r, float g,float b,float a,float multby){ float[] da = new float[((sa.length/3)*4)]; int vertex=0; for (int i=0;i<sa.length;i=i+3){ if (sa[i+2]>=1){ da[(vertex*4)+0]= r*multby*sa[i+2]; da[(vertex*4)+1]= g*multby*sa[i+2]; da[(vertex*4)+2]= b*multby*sa[i+2]; da[(vertex*4)+3]= a*multby*sa[i+2]; }else if (sa[i+2]<=-1){ float divisor = (multby*(-sa[i+2])); da[(vertex*4)+0]= r / divisor; da[(vertex*4)+1]= g / divisor; da[(vertex*4)+2]= b / divisor; da[(vertex*4)+3]= a / divisor; }else{ da[(vertex*4)+0]= r; da[(vertex*4)+1]= g; da[(vertex*4)+2]= b; da[(vertex*4)+3]= a; } vertex = vertex+1; } return FloatBuffer.wrap(da); } public float[] ScaleFloats(float[] va,float s){ float[] reta= new float[va.length]; for (int i=0;i<va.length;i=i+1){ reta[i]=va[i]*s; } return reta; } public float[] ScaleFloats(float[] va,float sx,float sy){ float[] reta= new float[va.length]; int cnt = 0; for (int i=0;i<va.length;i=i+1){ if (cnt==0){reta[i]=va[i]*sx;} else if (cnt==1){reta[i]=va[i]*sy;} else if (cnt==2){reta[i]=va[i];} cnt = cnt +1;if (cnt>2){cnt=0;} } return reta; } }

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• [C#] Convert string to double with 2 digit after decimal separator

  - by st.stoqnov

  All began with these simple lines of code: string s = "16.9"; double d = Convert.ToDouble(s); d*=100; The result should be 1690.0, but it's not. d is equal to 1689.9999999999998. All I want to do is to round a double to value with 2 digit after decimal separator. Here is my function. private double RoundFloat(double Value) { float sign = (Value < 0) ? -0.01f : 0.01f; if (Math.Abs(Value) < 0.00001) Value = 0; string SVal = Value.ToString(); string DecimalSeparator = System.Globalization.CultureInfo.CurrentCulture.NumberFormat.CurrencyDecimalSeparator; int i = SVal.IndexOf(DecimalSeparator); if (i > 0) { int SRnd; try { // ????? ??????? ????? ???? ?????????? ?????????? SRnd = Convert.ToInt32(SVal.Substring(i + 3, 1)); } catch { SRnd = 0; } if (SVal.Length > i + 3) SVal = SVal.Substring(0, i + 3); //SVal += "00001"; try { double result = (SRnd >= 5) ? Convert.ToDouble(SVal) + sign : Convert.ToDouble(SVal); //result = Math.Round(result, 2); return result; } catch { return 0; } } else { return Value; } But again the same problem, converting from string to double is not working as I want. A workaround to this problem is to concatenate "00001" to the string and then use the Math.Round function (commented in the example above). This double value multiplied to 100 (as integer) is send to a device (cash register) and this values must be correct. I am using VS2005 + .NET CF 2.0 Is there another more "elegant" solution, I am not happy with this one.

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• understanding floating point variables

  - by Syom

  There is some problem, i can't understand anyway. look at this code please <script type="text/javascript"> function math(x) { var y; y = x*10; alert(y); } </script> <input type="button" onclick="math(0.011)"> What must be alerted after i click on button? i think 0.11, but no, it alerts 0.10999999999999999 explain please this behavior. thanks in advance

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• How to allow my Asp.net MVC 3 web app using MathJax to accept user input $x<y>z$ ?

  - by Recycle Bin

  I am developing a mathematics site using Asp.Net MVC 3 + Razor + MathJax. MathJax is a javascript library to render TeX or LaTeX codes on the web browser. And TeX or LaTeX codes represent mathematics contents such as an inline math $y=mx+c$ and a displayed math \[y=mx+c\]. Right now my site can accept input, for example, $x<y$. However it cannot accept $x<y>z$ because the framework regards this input is vulnerable to XSS and XSRF. Shortly speaking, what I should do to accomplish what I want but it does not open security vulnerability.

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• Smooth animation using MatrixTransform?

  - by Mattias Konradsson

  I'm trying to do an Matrix animation where I both scale and transpose a canvas at the same time. The only approach I found was using a MatrixTransform and MatrixAnimationUsingKeyFrames. Since there doesnt seem to be any interpolation for matrices built in (only for path/rotate) it seems the only choice is to try and build the interpolation and DiscreteMatrixKeyFrame's yourself. I did a basic implementation of this but it isnt exactly smooth and I'm not sure if this is the best way and how to handle framerates etc. Anyone have suggestions for improvement? Here's the code: MatrixAnimationUsingKeyFrames anim = new MatrixAnimationUsingKeyFrames(); int duration = 1; anim.KeyFrames = Interpolate(new Point(0, 0), centerPoint, 1, factor,100,duration); this.matrixTransform.BeginAnimation(MatrixTransform.MatrixProperty, anim,HandoffBehavior.Compose); public MatrixKeyFrameCollection Interpolate(Point startPoint, Point endPoint, double startScale, double endScale, double framerate,double duration) { MatrixKeyFrameCollection keyframes = new MatrixKeyFrameCollection(); double steps = duration * framerate; double milliSeconds = 1000 / framerate; double timeCounter = 0; double diffX = Math.Abs(startPoint.X- endPoint.X); double xStep = diffX / steps; double diffY = Math.Abs(startPoint.Y - endPoint.Y); double yStep = diffY / steps; double diffScale= Math.Abs(startScale- endScale); double scaleStep = diffScale / steps; if (endPoint.Y < startPoint.Y) { yStep = -yStep; } if (endPoint.X < startPoint.X) { xStep = -xStep; } if (endScale < startScale) { scaleStep = -scaleStep; } Point currentPoint = new Point(); double currentScale = startScale; for (int i = 0; i < steps; i++) { keyframes.Add(new DiscreteMatrixKeyFrame(new Matrix(currentScale, 0, 0, currentScale, currentPoint.X, currentPoint.Y), KeyTime.FromTimeSpan(TimeSpan.FromMilliseconds(timeCounter)))); currentPoint.X += xStep; currentPoint.Y += yStep; currentScale += scaleStep; timeCounter += milliSeconds; } keyframes.Add(new DiscreteMatrixKeyFrame(new Matrix(endScale, 0, 0, endScale, endPoint.X, endPoint.Y), KeyTime.FromTimeSpan(TimeSpan.FromMilliseconds(0)))); return keyframes; }

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• LaTeX support with Movable Type 5?

  - by Timmy

  Is there latex math support with movable type 5?

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• Firefox throwing a exception with HTML Canvas putImageData

  - by mr.doob

  So I was working on this little javascript experiment and I needed a widget to track the FPS of it. I ported a widget I've been using with Actionscript 3 to Javascript and it seems to be working fine with Chrome/Safari but on Firefox is throwing an exception. This is the experiment: Depth of Field This is the error: [Exception... "An invalid or illegal string was specified" code: "12" nsresult: "0x8053000c (NS_ERROR_DOM_SYNTAX_ERR)" location: "http://mrdoob.com/projects/chromeexperiments/depth_of_field__debug/js/net/hires/debug/Stats.js Line: 105"] The line that is complaning about is this one: graph.putImageData(graphData, 1, 0, 0, 0, 69, 50); Which is a crappy code to "scroll" the bitmap pixels. The idea is that I only draw a few pixels on the left of the bitmap and then on the next frame I copy the whole bitmap and paste it on pixel to the right. This error usually is thrown because you're pasting a bitmap bigger than the source and it's going off the limits, but in theory that shouldn't be the case as I'm defining 69 as the width of the rectangle to paste (being the bitmap 70px wide). And this is full code: var Stats = { baseFps: null, timer: null, timerStart: null, timerLast: null, fps: null, ms: null, container: null, fpsText: null, msText: null, memText: null, memMaxText: null, graph: null, graphData: null, init: function(userfps) { baseFps = userfps; timer = 0; timerStart = new Date() - 0; timerLast = 0; fps = 0; ms = 0; container = document.createElement("div"); container.style.fontFamily = 'Arial'; container.style.fontSize = '10px'; container.style.backgroundColor = '#000033'; container.style.width = '70px'; container.style.paddingTop = '2px'; fpsText = document.createElement("div"); fpsText.style.color = '#ffff00'; fpsText.style.marginLeft = '3px'; fpsText.style.marginBottom = '-3px'; fpsText.innerHTML = "FPS:"; container.appendChild(fpsText); msText = document.createElement("div"); msText.style.color = '#00ff00'; msText.style.marginLeft = '3px'; msText.style.marginBottom = '-3px'; msText.innerHTML = "MS:"; container.appendChild(msText); memText = document.createElement("div"); memText.style.color = '#00ffff'; memText.style.marginLeft = '3px'; memText.style.marginBottom = '-3px'; memText.innerHTML = "MEM:"; container.appendChild(memText); memMaxText = document.createElement("div"); memMaxText.style.color = '#ff0070'; memMaxText.style.marginLeft = '3px'; memMaxText.style.marginBottom = '3px'; memMaxText.innerHTML = "MAX:"; container.appendChild(memMaxText); var canvas = document.createElement("canvas"); canvas.width = 70; canvas.height = 50; container.appendChild(canvas); graph = canvas.getContext("2d"); graph.fillStyle = '#000033'; graph.fillRect(0, 0, canvas.width, canvas.height ); graphData = graph.getImageData(0, 0, canvas.width, canvas.height); setInterval(this.update, 1000/baseFps); return container; }, update: function() { timer = new Date() - timerStart; if ((timer - 1000) > timerLast) { fpsText.innerHTML = "FPS: " + fps + " / " + baseFps; timerLast = timer; graph.putImageData(graphData, 1, 0, 0, 0, 69, 50); graph.fillRect(0,0,1,50); graphData = graph.getImageData(0, 0, 70, 50); var index = ( Math.floor(Math.min(50, (fps / baseFps) * 50)) * 280 /* 70 * 4 */ ); graphData.data[index] = graphData.data[index + 1] = 256; index = ( Math.floor(Math.min(50, 50 - (timer - ms) * .5)) * 280 /* 70 * 4 */ ); graphData.data[index + 1] = 256; graph.putImageData (graphData, 0, 0); fps = 0; } ++fps; msText.innerHTML = "MS: " + (timer - ms); ms = timer; } } Any ideas? Thanks in advance.

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• jump search algorithm

  - by davit-datuashvili

  i am doing jump search algorithm but it show me that element is not in array while it is here is code import java.math.*; public class jamp { public static int min(int a,int b){ return a } public static void main(String[]args){ int a[]=new int[]{3,7,9,12,14,15,16,17,18}; int l=14; System.out.println(jumpsearch(a,a.length,l)); } public static int jumpsearch(int a[],int n, int l ){ int t=0; int b=(int)Math.sqrt(n); while (a[min(b,n)-1]=n) return -1 ; } while (a[t] return -1 ; if ( a[t]==l) { return t; } } return -1; } } please help

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• Java :moving ball with angle ?

  - by Meko

  Hi all.I am started to learn game physics and I am trying to move ball with an angle.But it does not change its angle .Java coordinate sydstem is a little different and i think my problem is there.Here my codes this is for calculating x and y speed scale_X= Math.sin(angle); scale_Y=Math.cos(angle); velosity_X=(speed*scale_X); velosity_Y=(speed*scale_Y); This is for moving ball in run() function ball.posX =ball.posX+(int)velosity_X; ball.posY=ball.posY+(int)velosity_Y; I used (int)velosity_X and (int)velosity_Y because in ball class I draw object g.drawOval(posX, posX, width, height); and here g.drawOval requares int.I dont know is it problem or not. Also if I use angle 30 it goes +X and +Y but if I use angle 35 it goes -X and -Y. I didnot figure out how work coordinate system on java.

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• Canvas context used but not updated on canvas

  - by John Doe

  I am developing an small html5 game, where I have the following code: if(object.blocks){ var blocks = object.blocks, that = this; each(blocks,function(index){ that.blocks.push(new Block(this[index])); }); } I receive an object with some configuration and instantiate blocks with it. It works fine, but the Block class has an method, called draw: this.draw = function (ctx){ if(ctx){ var colors = ['#FF0000','#FFFF00','#0000FF','#00FF00'], color = Math.round(Math.random() * colors.length-1); ctx.fillStyle = colors[color]; ctx.fillRect(this.x,this.y,this.width,this.height); } }; It was working before I moved it into the Block class, but now it draws nothing. This is the code that calls draw: render: function(ctx){ each(this.blocks,function(index){ this[index].draw(ctx); }); } The context comes from the html page, from the main canvas.

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• Web service creates stack overflow

  - by mouthpiec

  I have an application that when executed as a windows application works fine, but when converted to a web service, in some instances (which were tested successfully) by the windows app) creates a stack overflow. Do you have an idea of what can cause this? (Note that it works fine when the web service is placed on the localhost). Could it be that the stack size of a Web Service is smaller than that of a Window Application? UPDATE The below is the code in which I am getting a stack overflow error private bool CheckifPixelsNeighbour(Pixel c1, Pixel c2, int DistanceAllowed) { bool Neighbour = false; if ((Math.Abs(c1.X - c2.X) <= DistanceAllowed) && Math.Abs(c1.Y - c2.Y) <= DistanceAllowed) { Neighbour = true; } return Neighbour; }

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• LLVM: bitcode with llvm-gcc (mingw) for windows

  - by TheShow

  Hi, i'm currently building a small JIT compiler. For the language I need a runtime library for some special math functions. I think the best would be to compile the lib to bitcode and link it. The compiler should be integrated in a product and as of this, it must work under windows (VC10, 64bit). So is it possible to build the math lib with the mingw llvm-gcc build an link it later with the JITed Code? Or are there any problems regarding the portability of the bitcode build with llvm-gcc under mingw? If there are problems, what solution would you suggest?

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• Set Theory and .NET

  - by MasterMax1313

  Recently I came across a situation where set theory and set math fit what I was doing to the letter (granted there was an easier way to accomplish what I needed - i.e. LINQ - but I didn't think of that at the time). However I didn't know of any generic set libraries. Granted IEnumerables provide some set operations (Union, etc.), but nothing like Intersection or set comparison. Can anyone point out something that fits here? Something that implements set math using a generic type?

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• Stochastic calculus library in python

  - by LeMiz

  Hello, I am looking for a python library that would allow me to compute stochastic calculus stuff, like the (conditional) expectation of a random process I would define the diffusion. I had a look a at simpy (simpy.sourceforge.net), but it does not seem to cover my needs. This is for quick prototyping and experimentation. In java, I used with some success the (now inactive) http://martingale.berlios.de/Martingale.html library. The problem is not difficult in itself, but there is a lot non trivial, boilerplate things to do (efficient memory use, variable reduction techniques, and so on). Ideally, I would be able to write something like this (just illustrative): def my_diffusion(t, dt, past_values, world, **kwargs): W1, W2 = world.correlated_brownians_pair(correlation=kwargs['rho']) X = past_values[-1] sigma_1 = kwargs['sigma1'] sigma_2 = kwargs['sigma2'] dX = kwargs['mu'] * X * dt + sigma_1 * W1 * X * math.sqrt(dt) + sigma_2 * W2 * X * X * math.sqrt(dt) return X + dX X = RandomProcess(diffusion=my_diffusion, x0 = 1.0) print X.expectancy(T=252, dt = 1./252., N_simul= 50000, world=World(random_generator='sobol'), sigma1 = 0.3, sigma2 = 0.01, rho=-0.1) Does someone knows of something else than reimplementing it in numpy for example ?

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