Search Results

Search found 10194 results on 408 pages for 'raw types'.

Page 1/408 | 1 2 3 4 5 6 7 8 9 10 11 12  | Next Page >

  • 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!

    Read the article

  • free Raw-File Converter/Editor

    - by RCIX
    I have RAW files output by a program with a specific set of properties (Photoshop RAW, 16 bits, IBM PC byte order, no header, 1 non-interleaved channel, variable sizes like 257X257 or 129X513); does anyone know of a free tool that will allow me to convert to and from this format, and possibly do basic editing (selection, copy/paste, rotation of selection)? I've tried Picasa, XNView, and Paint Shop Pro 7 and none of them work properly. The closest i get is Paint Shop Pro which will at least make a serviceable attempt to open these files but i can't set all of the proper settings. XNView just might be able to edit it if i can figure out how to change the open settings for a particular raw file. So my questions at current are: how do i tell XNView to open a raw file a particular way? Failing that, is there any free tool that can open Photoshop-RAW files with the above settings (that's not photoshop)? If it helps, i'm trying to import/export/edit hieghtmap data for maps for Supreme Commander.

    Read the article

  • SQL SERVER – Wait Stats – Wait Types – Wait Queues – Day 0 of 28

    - by pinaldave
    This blog post will have running account of the all the blog post I will be doing in this month related to SQL Server Wait Types and Wait Queues. SQL SERVER – Introduction to Wait Stats and Wait Types – Wait Type – Day 1 of 28 SQL SERVER – Signal Wait Time Introduction with Simple Example – Wait Type – Day 2 of 28 SQL SERVER – DMV – sys.dm_os_wait_stats Explanation – Wait Type – Day 3 of 28 SQL SERVER – DMV – sys.dm_os_waiting_tasks and sys.dm_exec_requests – Wait Type – Day 4 of 28 SQL SERVER – Capturing Wait Types and Wait Stats Information at Interval – Wait Type – Day 5 of 28 SQL SERVER – CXPACKET – Parallelism – Usual Solution – Wait Type – Day 6 of 28 SQL SERVER – CXPACKET – Parallelism – Advanced Solution – Wait Type – Day 7 of 28 SQL SERVER – SOS_SCHEDULER_YIELD – Wait Type – Day 8 of 28 SQL SERVER – PAGEIOLATCH_DT, PAGEIOLATCH_EX, PAGEIOLATCH_KP, PAGEIOLATCH_SH, PAGEIOLATCH_UP – Wait Type – Day 9 of 28 SQL SERVER – IO_COMPLETION – Wait Type – Day 10 of 28 SQL SERVER – ASYNC_IO_COMPLETION – Wait Type – Day 11 of 28 SQL SERVER – PAGELATCH_DT, PAGELATCH_EX, PAGELATCH_KP, PAGELATCH_SH, PAGELATCH_UP – Wait Type – Day 12 of 28 SQL SERVER – FT_IFTS_SCHEDULER_IDLE_WAIT – Full Text – Wait Type – Day 13 of 28 SQL SERVER – BACKUPIO, BACKUPBUFFER – Wait Type – Day 14 of 28 SQL SERVER – LCK_M_XXX – Wait Type – Day 15 of 28 Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Optimization, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

    Read the article

  • SQL SERVER – Wait Stats – Wait Types – Wait Queues – Day 0 of 28

    - by pinaldave
    This blog post will have running account of the all the blog post I will be doing in this month related to SQL Server Wait Types and Wait Queues. SQL SERVER – Introduction to Wait Stats and Wait Types – Wait Type – Day 1 of 28 SQL SERVER – Single Wait Time Introduction with Simple Example – Wait Type – Day 2 of 28 Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

    Read the article

  • SQL SERVER – Guest Post – Jacob Sebastian – Filestream – Wait Types – Wait Queues – Day 22 of 28

    - by pinaldave
    Jacob Sebastian is a SQL Server MVP, Author, Speaker and Trainer. Jacob is one of the top rated expert community. Jacob wrote the book The Art of XSD – SQL Server XML Schema Collections and wrote the XML Chapter in SQL Server 2008 Bible. See his Blog | Profile. He is currently researching on the subject of Filestream and have submitted this interesting article on the very subject. What is FILESTREAM? FILESTREAM is a new feature introduced in SQL Server 2008 which provides an efficient storage and management option for BLOB data. Many applications that deal with BLOB data today stores them in the file system and stores the path to the file in the relational tables. Storing BLOB data in the file system is more efficient that storing them in the database. However, this brings up a few disadvantages as well. When the BLOB data is stored in the file system, it is hard to ensure transactional consistency between the file system data and relational data. Some applications store the BLOB data within the database to overcome the limitations mentioned earlier. This approach ensures transactional consistency between the relational data and BLOB data, but is very bad in terms of performance. FILESTREAM combines the benefits of both approaches mentioned above without the disadvantages we examined. FILESTREAM stores the BLOB data in the file system (thus takes advantage of the IO Streaming capabilities of NTFS) and ensures transactional consistency between the BLOB data in the file system and the relational data in the database. For more information on the FILESTREAM feature, visit: http://beyondrelational.com/filestream/default.aspx FILESTREAM Wait Types Since this series is on the different SQL Server wait types, let us take a look at the various wait types that are related to the FILESTREAM feature. FS_FC_RWLOCK This wait type is generated by FILESTREAM Garbage Collector. This occurs when Garbage collection is disabled prior to a backup/restore operation or when a garbage collection cycle is being executed. FS_GARBAGE_COLLECTOR_SHUTDOWN This wait type occurs when during the cleanup process of a garbage collection cycle. It indicates that that garbage collector is waiting for the cleanup tasks to be completed. FS_HEADER_RWLOCK This wait type indicates that the process is waiting for obtaining access to the FILESTREAM header file for read or write operation. The FILESTREAM header is a disk file located in the FILESTREAM data container and is named “filestream.hdr”. FS_LOGTRUNC_RWLOCK This wait type indicates that the process is trying to perform a FILESTREAM log truncation related operation. It can be either a log truncate operation or to disable log truncation prior to a backup or restore operation. FSA_FORCE_OWN_XACT This wait type occurs when a FILESTREAM file I/O operation needs to bind to the associated transaction, but the transaction is currently owned by another session. FSAGENT This wait type occurs when a FILESTREAM file I/O operation is waiting for a FILESTREAM agent resource that is being used by another file I/O operation. FSTR_CONFIG_MUTEX This wait type occurs when there is a wait for another FILESTREAM feature reconfiguration to be completed. FSTR_CONFIG_RWLOCK This wait type occurs when there is a wait to serialize access to the FILESTREAM configuration parameters. Waits and Performance System waits has got a direct relationship with the overall performance. In most cases, when waits increase the performance degrades. SQL Server documentation does not say much about how we can reduce these waits. However, following the FILESTREAM best practices will help you to improve the overall performance and reduce the wait types to a good extend. Read all the post in the Wait Types and Queue series. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, Readers Contribution, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology Tagged: Filestream

    Read the article

  • SQLAuthority News – Online Webcast How to Identify Resource Bottlenecks – Wait Types and Queues

    - by pinaldave
    As all of you know I have been working a recently on the subject SQL Server Wait Statistics, the reason is since I have published book on this subject SQL Wait Stats Joes 2 Pros: SQL Performance Tuning Techniques Using Wait Statistics, Types & Queues [Amazon] | [Flipkart] | [Kindle], lots of question and answers I am encountering. When I was writing the book, I kept version 1 of the book in front of me. I wanted to write something which one can use right away. I wanted to create an primer for everybody who have not explored wait stats method of performance tuning. Well, the books have been very well received and in fact we ran out of huge stock 2 times in India so far and once in USA during SQLPASS. I have received so many questions on this subject that I feel I can write one more book of the same size. I have been asked if I can create videos which can go along with this book. Personally I am working with SQL Server 2012 CTP3 and there are so many new wait types, I feel the subject of wait stats is going to be very very crucial in next version of SQL Server. If you have not started learning about this subject, I suggest you at least start exploring this right now. Learn how to begin on this subject atleast as when the next version comes in, you know how to read DMVs. I will be presenting on the same subject of performance tuning by wait stats in webcast embarcadero SQL Server Community Webinar. Here are few topics which we will be covering during the webinar. Beginning with SQL Wait Stats Understanding various aspect of SQL Wait Stats Understanding Query Life Cycle Identifying three TOP wait Stats Resolution of the common 3 wait types and queues Details of the webcast: How to Identify Resource Bottlenecks – Wait Types and Queues Date and Time: Wednesday, November 2, 11:00 AM PDT Registration Link I thank embarcadero for organizing opportunity for me to share my experience on subject of wait stats and connecting me with community to further take this subject to next level. One more interesting thing, I will ask one question at the end of the webinar and I will be giving away 5 copy of my SQL Wait Stats print book to first five correct answers. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: About Me, Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

    Read the article

  • Create "raw disk file" from WIM file

    - by Joe Baltimore
    First timer here. I've searched around here, but haven't found a question like the one I have. Apologies if I missed it. The challenge at hand: produce a "raw disk image file" from a given WIM file. What I am pursuing so far is to use imagex.exe with the "/apply" operation to take the WIM and lay it down in a directory on a server. That seems to produce all the necessary "stuff" I need in that directory. How would I take that content and produce a "raw disk image file"? I'm told the definition of "raw disk image file" is a block-by-block copy of the disk image, which I hope is the output of the "imagex.exe /apply" command I use currently, but stored in a single file I can hand back to another system in our solution. imagex.exe /apply image.wim 1 R:\WimImagePoint I would like to take the contents of R:\WimImagePoint and produce the elusive (to me) "raw disk image file". ISO is not what they want, nor is anything requiring winPE. Any pointers? External utilities' references are welcome. Would like to avoid unmanaged code solutions as much as possible, but will entertain them if that's the only route. Also, I am not married to the idea of imagex /apply as the starting point, it's just the comfort zone so far.

    Read the article

  • Command line raw image processing tools in Linux?

    - by ???
    I'm wondering if there is any command to process raw images, for example, cat raw1.img | raw2jpg -w 640 -h 480 -pitch 1024 -pixelformat R8G8B8 and more examples: cat raw1.img raw2.img >y-merge.img tr='transpose -pitch 1024 -depth 24' cat <(cat raw1.img | $tr) <(cat raw2.img | $tr) | transpose -pitch 480 >x-merge.img and something like this: cat gamebitmap.dat | ( w=`readint32` h=`readint32` raw2png -w $w -h $h -depth 24 -pixelformat R8G8B8 ) | png2svg -extractoutline -fuzzy -error 8 -smooth Seems a little tricky, but is it possible? does ImageMagick support such raw formats?

    Read the article

  • SQL SERVER – Introduction to Wait Stats and Wait Types – Wait Type – Day 1 of 28

    - by pinaldave
    I have been working a lot on Wait Stats and Wait Types recently. Last Year, I requested blog readers to send me their respective server’s wait stats. I appreciate their kind response as I have received  Wait stats from my readers. I took each of the results and carefully analyzed them. I provided necessary feedback to the person who sent me his wait stats and wait types. Based on the feedbacks I got, many of the readers have tuned their server. After a while I got further feedbacks on my recommendations and again, I collected wait stats. I recorded the wait stats and my recommendations and did further research. At some point at time, there were more than 10 different round trips of the recommendations and suggestions. Finally, after six month of working my hands on performance tuning, I have collected some real world wisdom because of this. Now I plan to share my findings with all of you over here. Before anything else, please note that all of these are based on my personal observations and opinions. They may or may not match the theory available at other places. Some of the suggestions may not match your situation. Remember, every server is different and consequently, there is more than one solution to a particular problem. However, this series is written with kept wait stats in mind. While I was working on various performance tuning consultations, I did many more things than just tuning wait stats. Today we will discuss how to capture the wait stats. I use the script diagnostic script created by my friend and SQL Server Expert Glenn Berry to collect wait stats. Here is the script to collect the wait stats: -- Isolate top waits for server instance since last restart or statistics clear WITH Waits AS (SELECT wait_type, wait_time_ms / 1000. AS wait_time_s, 100. * wait_time_ms / SUM(wait_time_ms) OVER() AS pct, ROW_NUMBER() OVER(ORDER BY wait_time_ms DESC) AS rn FROM sys.dm_os_wait_stats WHERE wait_type NOT IN ('CLR_SEMAPHORE','LAZYWRITER_SLEEP','RESOURCE_QUEUE','SLEEP_TASK' ,'SLEEP_SYSTEMTASK','SQLTRACE_BUFFER_FLUSH','WAITFOR', 'LOGMGR_QUEUE','CHECKPOINT_QUEUE' ,'REQUEST_FOR_DEADLOCK_SEARCH','XE_TIMER_EVENT','BROKER_TO_FLUSH','BROKER_TASK_STOP','CLR_MANUAL_EVENT' ,'CLR_AUTO_EVENT','DISPATCHER_QUEUE_SEMAPHORE', 'FT_IFTS_SCHEDULER_IDLE_WAIT' ,'XE_DISPATCHER_WAIT', 'XE_DISPATCHER_JOIN', 'SQLTRACE_INCREMENTAL_FLUSH_SLEEP')) SELECT W1.wait_type, CAST(W1.wait_time_s AS DECIMAL(12, 2)) AS wait_time_s, CAST(W1.pct AS DECIMAL(12, 2)) AS pct, CAST(SUM(W2.pct) AS DECIMAL(12, 2)) AS running_pct FROM Waits AS W1 INNER JOIN Waits AS W2 ON W2.rn <= W1.rn GROUP BY W1.rn, W1.wait_type, W1.wait_time_s, W1.pct HAVING SUM(W2.pct) - W1.pct < 99 OPTION (RECOMPILE); -- percentage threshold GO This script uses Dynamic Management View sys.dm_os_wait_stats to collect the wait stats. It omits the system-related wait stats which are not useful to diagnose performance-related bottleneck. Additionally, not OPTION (RECOMPILE) at the end of the DMV will ensure that every time the query runs, it retrieves new data and not the cached data. This dynamic management view collects all the information since the time when the SQL Server services have been restarted. You can also manually clear the wait stats using the following command: DBCC SQLPERF('sys.dm_os_wait_stats', CLEAR); Once the wait stats are collected, we can start analysis them and try to see what is causing any particular wait stats to achieve higher percentages than the others. Many waits stats are related to one another. When the CPU pressure is high, all the CPU-related wait stats show up on top. But when that is fixed, all the wait stats related to the CPU start showing reasonable percentages. It is difficult to have a sure solution, but there are good indications and good suggestions on how to solve this. I will keep this blog post updated as I will post more details about wait stats and how I reduce them. The reference to Book On Line is over here. Of course, I have selected February to run this Wait Stats series. I am already cheating by having the smallest month to run this series. :) Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: DMV, Pinal Dave, PostADay, SQL, SQL Authority, SQL Optimization, SQL Performance, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

    Read the article

  • Software for handling camera RAW-files

    - by Eikern
    I use a digital SLR as most other photographers do today and have quickly realised that capturing images using camera-RAW files is the way to go. Personally I use Adobe Lightroom to handle my photo library, but I know there are other software available like Apple Aperture. These applications are quite hard to use for a novice, and are quite expensive too. I've often recommended other photographers to switch to camera-raw, but they won't do it because Windows can't handle it natively. Are there any free or cheaper applications out there that can do simple file handling and adjustments? Preferably so simple that my mom can do it. I know Nikon offers a codec that allows you to view NEF-files natively inside Windows, but still limits the uses of the file and slows the system down if the file is big. Does anybody know of a drag-and-drop application that converts camera-raw to JPG on-the-fly? In case I or someone would need to upload an image to the web or use it inside a word-document. Thanks.

    Read the article

  • Read video from dvd in RAW filesystem

    - by kpinhack
    Hallo, i've got some dvds that were recorded on a dvd recorder. I can not read those dvds on windows PCs (i tried multiple PCs). The properties of the discs say that the filesystem of the disc is RAW and i think that is the reason why windows does not read the disc. If that is true, what can i do to read the dvds ? Or what else could be the problem ? EDIT: The windows PCs i tried play back regular DVDs without any problem, and the "RAW" dvds recorded with the dvd recorder will not play on a standalone dvd player. Thank you!

    Read the article

  • Types issue in F#

    - by Andry
    Hello! In my ongoing adventure deep diving into f# I am understanding a lot of this powerful language but there are things that I still do not understand so clearly. One of the most important issues I need to master is types. Well the book I am reading is very straight forward and introduces entities and main functionalities with a direct approach. The first thing I could get start with is types. It introduces the main types as list, option, tuples, and so on... It is clearly underlined that all these types are IMMUTABLE for many reasons regarding functional programming and data consistance in functional programing. Well, no problems until now... But now I am getting started with Concrete Types... Well... I have problems in managing with types like list, option, tuples, types created through new operator and concrete types created using type keyword (for abbreviations, concrete types...). So my question is: how can I efficently catalogue/distinguish all types of data in f#???? I can create a perfect separation among types in C#, VB.NET... FOr example in VB.NET there are value and reference types while in C# there are only references and also int, double are treated as objects (they are objects while in VB.NET a value type is not a object and there is a split in types for this reason). Well in F# I cannot create such differences among types in the language. Can you help me? I hope I was clear.

    Read the article

  • computing hash values, integral types versus struct/class

    - by aaa
    hello I would like to know if there is a difference in speed between computing hash value (for example std::map key) of primitive integral type, such as int64_t and pod type, for example struct { int16_t v[4]; };. I know this is going to implementation specific, so my question ultimately pertains to gnu standard library. Thanks

    Read the article

  • checksum in raw sockets and pcap

    - by hero
    i am using pcap library to sniff some packets, change their tcp data , and then inject my packet on the network. my question is: if i changed in the tcp data, should i recalculate the length field in the tcp header? should i also change the checksum? i read in a page on how to create raw sockets that if you set the tcp_checksum to 0, the kernel will automatically calculate it and fill it, is this true for windows machines also?

    Read the article

  • Windows 7 system drive says it is raw, but System Recovery starts without issues

    - by iulianchira
    I have been running Windows 7 RC1 since it was available a couple of months ago and had no issues whatsoever until today. When I start my laptop, Windows does not boot but instead Windows System Recovery starts. I've used diskpart to list the partitions on the drive and my system partition (c:) has a RAW filesystem. I really need to save all data on the disk as fast as I cant and I would really like not to have to reinstall my system.

    Read the article

  • Windows 7 system drive says it is raw, but System Recovery starts without issues

    - by Iulian Chira
    I have been running Windows 7 RC1 since it was available a couple of months ago and had no issues whatsoever until today. When I start my laptop, Windows does not boot but instead Windows System Recovery starts. I've used diskpart to list the partitions on the drive and my system partition (c:) has a RAW filesystem. I really need to save all data on the disk as fast as I cant and I would really like not to have to reinstall my system.

    Read the article

  • Raw Sockets on Android

    - by Tingo
    I want to create an application that runs on Android and uses Raw Sockets. I see there isn't any raw socket support in the java.net.* or the android.net.* libraries. Are raw sockets possible on Android?

    Read the article

  • List of Commonly Used Value Types in XNA Games

    - by Michael B. McLaughlin
    Most XNA programmers are concerned about generating garbage. More specifically about allocating GC-managed memory (GC stands for “garbage collector” and is both the name of the class that provides access to the garbage collector and an acronym for the garbage collector (as a concept) itself). Two of the major target platforms for XNA (Windows Phone 7 and Xbox 360) use variants of the .NET Compact Framework. On both variants, the GC runs under various circumstances (Windows Phone 7 and Xbox 360). Of concern to XNA programmers is the fact that it runs automatically after a fixed amount of GC-managed memory has been allocated (currently 1MB on both systems). Many beginning XNA programmers are unaware of what constitutes GC-managed memory, though. So here’s a quick overview. In .NET, there are two different “types” of types: value types and reference types. Only reference types are managed by the garbage collector. Value types are not managed by the garbage collector and are instead managed in other ways that are implementation dependent. For purposes of XNA programming, the important point is that they are not managed by the GC and thus do not, by themselves, increment that internal 1 MB allocation counter. (n.b. Structs are value types. If you have a struct that has a reference type as a member, then that reference type, when instantiated, will still be allocated in the GC-managed memory and will thus count against the 1 MB allocation counter. Putting it in a struct doesn’t change the fact that it gets allocated on the GC heap, but the struct itself is created outside of the GC’s purview). Both value types and reference types use the keyword ‘new’ to allocate a new instance of them. Sometimes this keyword is hidden by a method which creates new instances for you, e.g. XmlReader.Create. But the important thing to determine is whether or not you are dealing with a value types or a reference type. If it’s a value type, you can use the ‘new’ keyword to allocate new instances of that type without incrementing the GC allocation counter (except as above where it’s a struct with a reference type in it that is allocated by the constructor, but there are no .NET Framework or XNA Framework value types that do this so it would have to be a struct you created or that was in some third-party library you were using for that to even become an issue). The following is a list of most all of value types you are likely to use in a generic XNA game: AudioCategory (used with XACT; not available on WP7) AvatarExpression (Xbox 360 only, but exposed on Windows to ease Xbox development) bool BoundingBox BoundingSphere byte char Color DateTime decimal double any enum (System.Enum itself is a class, but all enums are value types such that there are no GC allocations for enums) float GamePadButtons GamePadCapabilities GamePadDPad GamePadState GamePadThumbSticks GamePadTriggers GestureSample int IntPtr (rarely but occasionally used in XNA) KeyboardState long Matrix MouseState nullable structs (anytime you see, e.g. int? something, that ‘?’ denotes a nullable struct, also called a nullable type) Plane Point Quaternion Ray Rectangle RenderTargetBinding sbyte (though I’ve never seen it used since most people would just use a short) short TimeSpan TouchCollection TouchLocation TouchPanelCapabilities uint ulong ushort Vector2 Vector3 Vector4 VertexBufferBinding VertexElement VertexPositionColor VertexPositionColorTexture VertexPositionNormalTexture VertexPositionTexture Viewport So there you have it. That’s not quite a complete list, mind you. For example: There are various structs in the .NET framework you might make use of. I left out everything from the Microsoft.Xna.Framework.Graphics.PackedVector namespace, since everything in there ventures into the realm of advanced XNA programming anyway (n.b. every single instantiable thing in that namespace is a struct and thus a value type; there are also two interfaces but interfaces cannot be instantiated at all and thus don’t figure in to this discussion). There are so many enums you’re likely to use (PlayerIndex, SpriteSortMode, SpriteEffects, SurfaceFormat, etc.) that including them would’ve flooded the list and reduced its utility. So I went with “any enum” and trust that you can figure out what the enums are (and it’s rare to use ‘new’ with an enum anyway). That list also doesn’t include any of the pre-defined static instances of some of the classes (e.g. BlendState.AlphaBlend, BlendState.Opaque, etc.) which are already allocated such that using them doesn’t cause any new allocations and therefore doesn’t increase that 1 MB counter. That list also has a few misleading things. VertexElement, VertexPositionColor, and all the other vertex types are structs. But you’re only likely to ever use them as an array (for use with VertexBuffer or DynamicVertexBuffer), and all arrays are reference types (even arrays of value types such as VertexPositionColor[ ] or int[ ]). * So that’s it for now. The note below may be a bit confusing (it deals with how the GC works and how arrays are managed in .NET). If so, you can probably safely ignore it for now but feel free to ask any questions regardless. * Arrays of value types (where the value type doesn’t contain any reference type members) are much faster for the GC to examine than arrays of reference types, so there is a definite benefit to using arrays of value types where it makes sense. But creating arrays of value types does cause the GC’s allocation counter to increase. Indeed, allocating a large array of a value type is one of the quickest ways to increment the allocation counter since a .NET array is a sequential block of memory. An array of reference types is just a sequential block of references (typically 4 bytes each) while an array of value types is a sequential block of instances of that type. So for an array of Vector3s it would be 12 bytes each since each float is 4 bytes and there are 3 in a Vector3; for an array of VertexPositionNormalTexture structs it would typically be 32 bytes each since it has two Vector3s and a Vector2. (Note that there are a few additional bytes taken up in the creation of an array, typically 12 but sometimes 16 or possibly even more, which depend on the implementation details of the array type on the particular platform the code is running on).

    Read the article

  • Recover hard disk from Raw format

    - by user1632736
    I have been all over the web today with no results. So my drive was encrypted (truecrypt) the whole drive where windows resided. I decided to partition it to install W8 and forgot it was encrypted. So the drive got damaged and not accessible. When connected to a computer it asks for formatting. Somehow I enabled the drive through TrueCrypt on another computer and I could see and get all the files. Then I decided to decrypt the drive thinking that everything would be back to normal. After decryption my drive is not NTFS it is in RAW format. I am trying every possible way to recover, and I am desperate enough to ask lol. I tried: ddrescue (linux) (not mountable, no signature, ntfsfix no good) testdisk (linux and windows) Sees the partitions but cant do anything Many recovery applications. etc etc. I read in different places that doing a quickformat to NTFS and then doing a data recovery might help. I would definitely like a second opinion. Any suggestion would be really helpful

    Read the article

  • casting raw strings python

    - by dave
    in python, given a variable which holds a string is there a quick way to cast that into another raw string variable? the following code should illustrate what im after... def checkEqual(x, y): print True if x==y else False line1 = "hurr..\n..durr" line2 = r"hurr..\n..durr" line3 = "%r"%line1 print "%s \n\n%s \n\n%s \n" % (line1, line2, line3) checkEqual(line2, line3) #outputs False checkEqual(line2, line3[1:-1]) #outputs True The closest I have found so far is the %r formatting flag which seems to return a raw string albeit within single quote marks. Is there any easier way to do this like a line3 = raw(line1) kind of thing?

    Read the article

  • How to migrate existing udp application to raw sockets

    - by osgx
    Hello Is there a tutorial for migration from plain udp sockets (linux, C99/C++, recv syscall is used) to the raw sockets? According to http://aschauf.landshut.org/fh/linux/udp_vs_raw/ch03s04.html raw socket is much faster than udp. Application is client-server. client is proprietary and must use exactly same procotol as it was with udp server. But server can be a bit faster with raw sockets. What parts of udp I must to implement in server? Is there a "quick migration" libraries?

    Read the article

  • Virtualbox: Raw linux partition not booting

    - by abalter
    I have a dual-boot laptop with Windows 7 and Ubuntu 12.04. I am trying to boot the ubuntu partition from windows using Virtualbox. I have successfully created the .vmdk, and created the virtual machine. However, I can't get it to boot (in Virtualbox). All I get is a black screen with the cursor in the top left. I wonder if I'm specifying the partitions correctly. My Ubuntu install has 3 partitions: \, \boot, \home. No swap partition. These are all in Disk 0, partitions 3,4,5 respectively. The command I used to create the .vmdk is: VBoxManage internalcommands createrawvmdk -filename C:\Users\abalter\.virtualbox\ubuntu.vmdk -rawdisk \\.\PhysicalDrive0 -partitions 3,4,5 Then I create a virtual machine based on that .vmdk. Why won't it boot?

    Read the article

1 2 3 4 5 6 7 8 9 10 11 12  | Next Page >