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在C宏中定义二维常量数组

macros gcc c

Aurélien Pierre · 技术社区 · 6 年前

我想在内存中加载一个静态数组,在稍后的循环、C99和更高版本中用作卷积内核。我试过了:

/** This is the outer product of
 * filter[5] = { 1.0f / 16.0f, 4.0f / 16.0f, 6.0f / 16.0f, 4.0f / 16.0f, 1.0f / 16.0f };
 * computed at once, outside of the pixels loops, saving 25 multiplications per pixel
 * */
#define filter[5][5] { {0.00390625f, 0.015625f, 0.0234375f, 0.015625f, 0.00390625f}, \
                       {0.01562500f, 0.062500f, 0.0937500f, 0.062500f, 0.01562500f}, \
                       {0.02343750f, 0.093750f, 0.1406250f, 0.093750f, 0.02343750f}, \
                       {0.01562500f, 0.062500f, 0.0937500f, 0.062500f, 0.01562500f}, \
                       {0.00390625f, 0.015625f, 0.0234375f, 0.015625f, 0.00390625f} }

GCC 8投诉:

error: expected expression before Â«Â {Â Â» token
 #define filter { {0.00390625f, 0.015625f, 0.0234375f, 0.015625f, 0.00390625f}, \

我已经找到了如何加载一维向量,但是如何使用二维向量呢?

编辑

最终目标是从中构建一个SIMD阵列:

static const __m128 filter_sse[5][5] = { { _mm_set1_ps(filter[0][0]),
                                         ... },
                                           ... };

并使用 static const float filter[5][5] 使它抱怨试图用非常量值设置常量。

3 回复 | 直到 6 年前

Craig Estey 6 年前

你忘了 = 之间 filter[5][5] 和 { { .

而且,就你所知, filter 不能是宏名,因为后面跟括号

而且,您需要类型(例如 float )

这里有一个清理过的版本:

#define DEFME float filter[5][5] = { \
    {0.00390625f, 0.015625f, 0.0234375f, 0.015625f, 0.00390625f}, \
    {0.01562500f, 0.062500f, 0.0937500f, 0.062500f, 0.01562500f}, \
    {0.02343750f, 0.093750f, 0.1406250f, 0.093750f, 0.02343750f}, \
    {0.01562500f, 0.062500f, 0.0937500f, 0.062500f, 0.01562500f}, \
    {0.00390625f, 0.015625f, 0.0234375f, 0.015625f, 0.00390625f} }

DEFME;

边注: 但是,为什么要使用宏?

0___________ 6 年前

从它的意义上抽象出来

#include <stdio.h>

#define myfilter(name) name[5][5] = { {0.00390625f, 0.015625f, 0.0234375f, 0.015625f, 0.00390625f}, \
                       {0.01562500f, 0.062500f, 0.0937500f, 0.062500f, 0.01562500f}, \
                       {0.02343750f, 0.093750f, 0.1406250f, 0.093750f, 0.02343750f}, \
                       {0.01562500f, 0.062500f, 0.0937500f, 0.062500f, 0.01562500f}, \
                       {0.00390625f, 0.015625f, 0.0234375f, 0.015625f, 0.00390625f} }

int main()
{
    const float myfilter(filter1);
    printf("%f\n", filter1[1][1]);

    return 0;
}

ryyker 6 年前

投诉是关于失踪的 = 操作员:

试试这个:

#define ARRAY filter[5][5] = { {0.00390625f, 0.015625f, 0.0234375f, 0.015625f, 0.00390625f},\
                       {0.01562500f, 0.062500f, 0.0937500f, 0.062500f, 0.01562500f},\
                       {0.02343750f, 0.093750f, 0.1406250f, 0.093750f, 0.02343750f},\
                       {0.01562500f, 0.062500f, 0.0937500f, 0.062500f, 0.01562500f},\
                       {0.00390625f, 0.015625f, 0.0234375f, 0.015625f, 0.00390625f} };

以后(例如)

const float ARRAY;
double a = filter[0][0];  //example assignment using #defined array