std::gslice

<metanoindex/>

 

C++

Linguaggio

Concetti

Libreria di Utilità

Stringhe

Contenitori

Algoritmi

Iteratori

Libreria matematca

Input/output

Localizzazione

Espressioni regolari (C++11)

Operazioni atomicche (C++11)

Multithreading (C++11)

 

Numeri libreria

Comuni funzioni matematiche

Virgola mobile ambiente

I numeri complessi

Array numerici

Pseudo-casuale generazione

In fase di compilazione aritmetica razionale (C++11)

Generici operazioni numeriche Original: Generic numeric operations The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

iota (C++11)

accumulate

inner_product

adjacent_difference

partial_sum

 

std::valarray

Membri funzioni Original: Member functions The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
valarray::valarray valarray::~valarray valarray::operator= valarray::operator[] valarray::swap valarray::size valarray::resize valarray::sum valarray::min valarray::max valarray::shift valarray::cshift valarray::apply	valarray::operator+ valarray::operator- valarray::operator~ valarray::operator! valarray::operator+= valarray::operator-= valarray::operator*= valarray::operator/= valarray::operator%= valarray::operator&= valarray::operator|= valarray::operator^= valarray::operator<<= valarray::operator>>=
Non membri funzioni Original: Non-member functions The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
swap (C++11) begin (C++11) end (C++11) abs exp log log10 pow sqrt sin cos tan asin acos atan atan2 sinh cosh tanh	operator* operator/ operator% operator+ operator- operator^ None operator& operator| operator<< operator>> operator&& operator None operator== operator!= operator< operator> operator<= operator>=
Helper classi Original: Helper classes The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
slice_array gslice_array indirect_array	slice gslice mask_array

 

<tbody> </tbody>

Elemento definito nell'header <valarray>
class gslice;

std::gslice è la classe selettore che identifica un sottoinsieme di indici std::valarray definiti da un multi-livello insieme di passi e dimensioni. Oggetti di std::gslice tipo possono essere usati come indici con operator[] valarray di selezionare, per esempio, le colonne di una matrice multidimensionale rappresentata come valarray.

Original:

std::gslice is the selector class that identifies a subset of std::valarray indices defined by a multi-level set of strides and sizes. Objects of type std::gslice can be used as indices with valarray's operator[] to select, for example, columns of a multidimensional array represented as a valarray.

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Dato il s valore iniziale, un elenco di passi i
j e una lista di dimensioni d
j, un std::gslice costruito da questi valori seleziona l'insieme di indici k
j=s+Σ
j(i
jd
j).

Original:

Given the starting value s, a list of strides i
j and a list of sizes d
j, a std::gslice constructed from these values selects the set of indices k
j=s+Σ
j(i
jd
j).

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Per esempio, con un gslice 3 indice iniziale, passi {19,4,1} e lunghezze {2,4,3} genera il seguente insieme di indici:

Original:

For example, a gslice with starting index 3, strides {19,4,1} and lengths {2,4,3} generates the following set of indices:

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

3 + 0*19 + 0*4 + 0*1 = 3, 3 + 0*19 + 0*4 + 1*1 = 4, 3 + 0*19 + 0*4 + 2*1 = 5, 3 + 0*19 + 1*4 + 0*1 = 7, 3 + 0*19 + 1*4 + 1*1 = 8, ... 3 + 1*19 + 3*4 + 2*1 = 36

È possibile costruire oggetti std::gslice che selezionano alcuni indici più di una volta: se il precedente esempio utilizzato il {1,1,1} passi, gli indici sarebbero stati {3, 4, 5, 4, 5, 6, ...} . Gslices in questione possono essere utilizzati solo come argomenti la versione const di std::valarray::operator[], altrimenti il ​​comportamento è indefinito.

Original:

It is possible to construct std::gslice objects that select some indices more than once: if the above example used the strides {1,1,1} , the indices would have been {3, 4, 5, 4, 5, 6, ...} . Such gslices may only be used as arguments to the const version of std::valarray::operator[], otherwise the behavior is undefined.

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Membri funzioni

(costruttore)	costruisce un gslice Original: constructs a gslice The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (metodo pubblico)
start	accede l'inizio della gslice Original: accesses the start of the gslice The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (metodo pubblico)
stride	accede alla serie di passi del gslice Original: accesses the array of strides of the gslice The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (metodo pubblico)
size	accede alla matrice di sizees del gslice Original: accesses the array of sizees of the gslice The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (metodo pubblico)

Esempio

dimostra l'uso di gslices affrontare colonne di una matrice 3D

Original:

demonstrates the use of gslices to address columns of a 3D array

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

#include <iostream>
#include <valarray>
void test_print(std::valarray<int>& v, int rows, int cols, int planes)
{
    for(int r=0; r<rows; ++r) {
        for(int c=0; c<cols; ++c) {
            for(int z=0; z<planes; ++z)
                std::cout << v[r*cols*planes + c*planes + z] << ' ';
            std::cout << '\n';
        }
        std::cout << '\n';
    }
}
int main()
{
    std::valarray<int> v = // 3d array: 2 x 4 x 3 elements
    { 111,112,113 , 121,122,123 , 131,132,133 , 141,142,143,
      211,212,213 , 221,222,223 , 231,232,233 , 241,242,243};
    // int ar3d[2][4][3]
    std::cout << "Initial 2x4x3 array:\n";
    test_print(v, 2, 4, 3);

    // update every value in the first columns of both planes
    v[std::gslice(0, {2, 4}, {4*3, 3})] = 1; // two level one strides of 12 elements
                                             // then four level two strides of 3 elements

    // subtract the third column from the second column in the 1st plane
    v[std::gslice(1, {1, 4}, {4*3, 3})] -= v[std::gslice(2, {1, 4}, {4*3, 3})];

    std::cout << "After column operations: \n";
    test_print(v, 2, 4, 3);
}

Output:

Initial 2x4x3 array:
111 112 113
121 122 123
131 132 133
141 142 143

211 212 213
221 222 223
231 232 233
241 242 243

After column operations:
1 -1 113
1 -1 123
1 -1 133
1 -1 143

1 212 213
1 222 223
1 232 233
1 242 243

Vedi anche

operator[]	get / set elemento valarray, fetta, o maschera Original: get/set valarray element, slice, or mask The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (metodo pubblico)
slice	BLAS-come una fetta di valarray: indice iniziale, lunghezza, passo Original: BLAS-like slice of a valarray: starting index, length, stride The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (classe)
gslice_array	proxy per un sottoinsieme di un valarray dopo aver applicato un gslice Original: proxy to a subset of a valarray after applying a gslice The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (classe template)