Быстрые искать значение в векторах MATLAB код Comparion

Question

Я использую MATLAB для поиска значения в двух векторах OCT_EXP, OCT_LOG, из двух входных значений u,v и выход val как условие

if ((u == 0)||(v == 0)) 
    val = 0; 
else 
    val = OCT_EXP(OCT_LOG(u) + OCT_LOG(v) + 1); 

Я попытался используйте три способа: нормальный путь (без направления), векторизованный путь и метод mex. Я ожидал, что метод mex будет лучшим способом, а затем векторизованным способом. Однако, когда я измеряю потребление времени, лучший способ (без векторизации) лучше всего, векторизованный путь - наихудший путь. Что происходит в моем коде? Спасибо всем

Я хочу рассмотреть скорость вверх функции, так как она будет называться много времени: 300.000 раз

Первый способ:

function val = gfmult_no_vec(u, v) 

OCT_EXP = [ 1, 2, 4, 8, 16, 32, 64, 128, 29, 58, 116, 232, 205, 135, 19, 38,... 
    76, 152, 45, 90, 180, 117, 234, 201, 143, 3, 6, 12, 24, 48, 96, 192, 157,... 
    39, 78, 156, 37, 74, 148, 53, 106, 212, 181, 119, 238, 193, 159, 35,... 
    70, 140, 5, 10, 20, 40, 80, 160, 93, 186, 105, 210, 185, 111, 222,... 
    161, 95, 190, 97, 194, 153, 47, 94, 188, 101, 202, 137, 15, 30, 60,... 
    120, 240, 253, 231, 211, 187, 107, 214, 177, 127, 254, 225, 223, 163,... 
    91, 182, 113, 226, 217, 175, 67, 134, 17, 34, 68, 136, 13, 26, 52,... 
    104, 208, 189, 103, 206, 129, 31, 62, 124, 248, 237, 199, 147, 59,... 
    118, 236, 197, 151, 51, 102, 204, 133, 23, 46, 92, 184, 109, 218,... 
    169, 79, 158, 33, 66, 132, 21, 42, 84, 168, 77, 154, 41, 82, 164, 85,... 
    170, 73, 146, 57, 114, 228, 213, 183, 115, 230, 209, 191, 99, 198,... 
    145, 63, 126, 252, 229, 215, 179, 123, 246, 241, 255, 227, 219, 171,... 
    75, 150, 49, 98, 196, 149, 55, 110, 220, 165, 87, 174, 65, 130, 25,... 
    50, 100, 200, 141, 7, 14, 28, 56, 112, 224, 221, 167, 83, 166, 81,... 
    162, 89, 178, 121, 242, 249, 239, 195, 155, 43, 86, 172, 69, 138, 9,... 
    18, 36, 72, 144, 61, 122, 244, 245, 247, 243, 251, 235, 203, 139, 11,... 
    22, 44, 88, 176, 125, 250, 233, 207, 131, 27, 54, 108, 216, 173, 71,... 
    142, 1, 2, 4, 8, 16, 32, 64, 128, 29, 58, 116, 232, 205, 135, 19, 38,... 
    76, 152, 45, 90, 180, 117, 234, 201, 143, 3, 6, 12, 24, 48, 96, 192,... 
    157, 39, 78, 156, 37, 74, 148, 53, 106, 212, 181, 119, 238, 193, 159,... 
    35, 70, 140, 5, 10, 20, 40, 80, 160, 93, 186, 105, 210, 185, 111,... 
    222, 161, 95, 190, 97, 194, 153, 47, 94, 188, 101, 202, 137, 15, 30,... 
    60, 120, 240, 253, 231, 211, 187, 107, 214, 177, 127, 254, 225, 223,... 
    163, 91, 182, 113, 226, 217, 175, 67, 134, 17, 34, 68, 136, 13, 26,... 
    52, 104, 208, 189, 103, 206, 129, 31, 62, 124, 248, 237, 199, 147,... 
    59, 118, 236, 197, 151, 51, 102, 204, 133, 23, 46, 92, 184, 109, 218,... 
    169, 79, 158, 33, 66, 132, 21, 42, 84, 168, 77, 154, 41, 82, 164, 85,... 
    170, 73, 146, 57, 114, 228, 213, 183, 115, 230, 209, 191, 99, 198,... 
    145, 63, 126, 252, 229, 215, 179, 123, 246, 241, 255, 227, 219, 171,... 
    75, 150, 49, 98, 196, 149, 55, 110, 220, 165, 87, 174, 65, 130, 25,... 
    50, 100, 200, 141, 7, 14, 28, 56, 112, 224, 221, 167, 83, 166, 81,... 
    162, 89, 178, 121, 242, 249, 239, 195, 155, 43, 86, 172, 69, 138, 9,... 
    18, 36, 72, 144, 61, 122, 244, 245, 247, 243, 251, 235, 203, 139, 11,... 
    22, 44, 88, 176, 125, 250, 233, 207, 131, 27, 54, 108, 216, 173, 71,... 
    142 ]; 

OCT_LOG = [ 0, 1, 25, 2, 50, 26, 198, 3, 223, 51, 238, 27, 104, 199, 75, 4,... 
    100, 224, 14, 52, 141, 239, 129, 28, 193, 105, 248, 200, 8, 76, 113, 5,... 
    138, 101, 47, 225, 36, 15, 33, 53, 147, 142, 218, 240, 18, 130, 69,... 
    29, 181, 194, 125, 106, 39, 249, 185, 201, 154, 9, 120, 77, 228, 114,... end 

    166, 6, 191, 139, 98, 102, 221, 48, 253, 226, 152, 37, 179, 16, 145,... 
    34, 136, 54, 208, 148, 206, 143, 150, 219, 189, 241, 210, 19, 92,... 
    131, 56, 70, 64, 30, 66, 182, 163, 195, 72, 126, 110, 107, 58, 40,... 
    84, 250, 133, 186, 61, 202, 94, 155, 159, 10, 21, 121, 43, 78, 212,... 
    229, 172, 115, 243, 167, 87, 7, 112, 192, 247, 140, 128, 99, 13, 103,... 
    74, 222, 237, 49, 197, 254, 24, 227, 165, 153, 119, 38, 184, 180,... 
    124, 17, 68, 146, 217, 35, 32, 137, 46, 55, 63, 209, 91, 149, 188,... 
    207, 205, 144, 135, 151, 178, 220, 252, 190, 97, 242, 86, 211, 171,... 
    20, 42, 93, 158, 132, 60, 57, 83, 71, 109, 65, 162, 31, 45, 67, 216,... 
    183, 123, 164, 118, 196, 23, 73, 236, 127, 12, 111, 246, 108, 161,... 
    59, 82, 41, 157, 85, 170, 251, 96, 134, 177, 187, 204, 62, 90, 203,... 
    89, 95, 176, 156, 169, 160, 81, 11, 245, 22, 235, 122, 117, 44, 215,... 
    79, 174, 213, 233, 230, 231, 173, 232, 116, 214, 244, 234, 168, 80,... 
    88, 175 ]; 

    if ((u == 0)||(v == 0)) 
     val = 0; 
    else 
     val = OCT_EXP(OCT_LOG(u) + OCT_LOG(v) + 1); 

Второй способ: Векторизованное способ

function val = gfmult_vec(u, v) 

OCT_EXP = [ 1, 2, 4, 8, 16, 32, 64, 128, 29, 58, 116, 232, 205, 135, 19, 38,... 
    76, 152, 45, 90, 180, 117, 234, 201, 143, 3, 6, 12, 24, 48, 96, 192, 157,... 
    39, 78, 156, 37, 74, 148, 53, 106, 212, 181, 119, 238, 193, 159, 35,... 
    70, 140, 5, 10, 20, 40, 80, 160, 93, 186, 105, 210, 185, 111, 222,... 
    161, 95, 190, 97, 194, 153, 47, 94, 188, 101, 202, 137, 15, 30, 60,... 
    120, 240, 253, 231, 211, 187, 107, 214, 177, 127, 254, 225, 223, 163,... 
    91, 182, 113, 226, 217, 175, 67, 134, 17, 34, 68, 136, 13, 26, 52,... 
    104, 208, 189, 103, 206, 129, 31, 62, 124, 248, 237, 199, 147, 59,... 
    118, 236, 197, 151, 51, 102, 204, 133, 23, 46, 92, 184, 109, 218,... 
    169, 79, 158, 33, 66, 132, 21, 42, 84, 168, 77, 154, 41, 82, 164, 85,... 
    170, 73, 146, 57, 114, 228, 213, 183, 115, 230, 209, 191, 99, 198,... 
    145, 63, 126, 252, 229, 215, 179, 123, 246, 241, 255, 227, 219, 171,... 
    75, 150, 49, 98, 196, 149, 55, 110, 220, 165, 87, 174, 65, 130, 25,... 
    50, 100, 200, 141, 7, 14, 28, 56, 112, 224, 221, 167, 83, 166, 81,... 
    162, 89, 178, 121, 242, 249, 239, 195, 155, 43, 86, 172, 69, 138, 9,... 
    18, 36, 72, 144, 61, 122, 244, 245, 247, 243, 251, 235, 203, 139, 11,... 
    22, 44, 88, 176, 125, 250, 233, 207, 131, 27, 54, 108, 216, 173, 71,... 
    142, 1, 2, 4, 8, 16, 32, 64, 128, 29, 58, 116, 232, 205, 135, 19, 38,... 
    76, 152, 45, 90, 180, 117, 234, 201, 143, 3, 6, 12, 24, 48, 96, 192,... 
    157, 39, 78, 156, 37, 74, 148, 53, 106, 212, 181, 119, 238, 193, 159,... 
    35, 70, 140, 5, 10, 20, 40, 80, 160, 93, 186, 105, 210, 185, 111,... 
    222, 161, 95, 190, 97, 194, 153, 47, 94, 188, 101, 202, 137, 15, 30,... 
    60, 120, 240, 253, 231, 211, 187, 107, 214, 177, 127, 254, 225, 223,... 
    163, 91, 182, 113, 226, 217, 175, 67, 134, 17, 34, 68, 136, 13, 26,... 
    52, 104, 208, 189, 103, 206, 129, 31, 62, 124, 248, 237, 199, 147,... 
    59, 118, 236, 197, 151, 51, 102, 204, 133, 23, 46, 92, 184, 109, 218,... 
    169, 79, 158, 33, 66, 132, 21, 42, 84, 168, 77, 154, 41, 82, 164, 85,... 
    170, 73, 146, 57, 114, 228, 213, 183, 115, 230, 209, 191, 99, 198,... 
    145, 63, 126, 252, 229, 215, 179, 123, 246, 241, 255, 227, 219, 171,... 
    75, 150, 49, 98, 196, 149, 55, 110, 220, 165, 87, 174, 65, 130, 25,... 
    50, 100, 200, 141, 7, 14, 28, 56, 112, 224, 221, 167, 83, 166, 81,... 
    162, 89, 178, 121, 242, 249, 239, 195, 155, 43, 86, 172, 69, 138, 9,... 
    18, 36, 72, 144, 61, 122, 244, 245, 247, 243, 251, 235, 203, 139, 11,... 
    22, 44, 88, 176, 125, 250, 233, 207, 131, 27, 54, 108, 216, 173, 71,... 
    142 ]; 

OCT_LOG = [ 0, 1, 25, 2, 50, 26, 198, 3, 223, 51, 238, 27, 104, 199, 75, 4,... 
    100, 224, 14, 52, 141, 239, 129, 28, 193, 105, 248, 200, 8, 76, 113, 5,... 
    138, 101, 47, 225, 36, 15, 33, 53, 147, 142, 218, 240, 18, 130, 69,... 
    29, 181, 194, 125, 106, 39, 249, 185, 201, 154, 9, 120, 77, 228, 114,... 
    166, 6, 191, 139, 98, 102, 221, 48, 253, 226, 152, 37, 179, 16, 145,... 
    34, 136, 54, 208, 148, 206, 143, 150, 219, 189, 241, 210, 19, 92,... 
    131, 56, 70, 64, 30, 66, 182, 163, 195, 72, 126, 110, 107, 58, 40,... 
    84, 250, 133, 186, 61, 202, 94, 155, 159, 10, 21, 121, 43, 78, 212,... 
    229, 172, 115, 243, 167, 87, 7, 112, 192, 247, 140, 128, 99, 13, 103,... 
    74, 222, 237, 49, 197, 254, 24, 227, 165, 153, 119, 38, 184, 180,... 
    124, 17, 68, 146, 217, 35, 32, 137, 46, 55, 63, 209, 91, 149, 188,... 
    207, 205, 144, 135, 151, 178, 220, 252, 190, 97, 242, 86, 211, 171,... 
    20, 42, 93, 158, 132, 60, 57, 83, 71, 109, 65, 162, 31, 45, 67, 216,... 
    183, 123, 164, 118, 196, 23, 73, 236, 127, 12, 111, 246, 108, 161,... 
    59, 82, 41, 157, 85, 170, 251, 96, 134, 177, 187, 204, 62, 90, 203,... 
    89, 95, 176, 156, 169, 160, 81, 11, 245, 22, 235, 122, 117, 44, 215,... 
    79, 174, 213, 233, 230, 231, 173, 232, 116, 214, 244, 234, 168, 80,... 
    88, 175 ]; 

    uv0 = (~((u == 0)|(v == 0))); 
    val = zeros(size(u)); 
    val(uv0) = OCT_EXP(OCT_LOG(u(uv0)) + OCT_LOG(v(uv0)) + 1); 
end 

последний способ: MEX код

#include "mex.h" 
double look_up(double u, double v) 
{ 
    double OCT_EXP [510] = { 1, 2, 4, 8, 16, 32, 64, 128, 29, 58, 116, 232, 205, 135, 19, 38, 
    76, 152, 45, 90, 180, 117, 234, 201, 143, 3, 6, 12, 24, 48, 96, 192, 157, 
    39, 78, 156, 37, 74, 148, 53, 106, 212, 181, 119, 238, 193, 159, 35, 
    70, 140, 5, 10, 20, 40, 80, 160, 93, 186, 105, 210, 185, 111, 222, 
    161, 95, 190, 97, 194, 153, 47, 94, 188, 101, 202, 137, 15, 30, 60, 
    120, 240, 253, 231, 211, 187, 107, 214, 177, 127, 254, 225, 223, 163, 
    91, 182, 113, 226, 217, 175, 67, 134, 17, 34, 68, 136, 13, 26, 52, 
    104, 208, 189, 103, 206, 129, 31, 62, 124, 248, 237, 199, 147, 59, 
    118, 236, 197, 151, 51, 102, 204, 133, 23, 46, 92, 184, 109, 218, 
    169, 79, 158, 33, 66, 132, 21, 42, 84, 168, 77, 154, 41, 82, 164, 85, 
    170, 73, 146, 57, 114, 228, 213, 183, 115, 230, 209, 191, 99, 198, 
    145, 63, 126, 252, 229, 215, 179, 123, 246, 241, 255, 227, 219, 171, 
    75, 150, 49, 98, 196, 149, 55, 110, 220, 165, 87, 174, 65, 130, 25, 
    50, 100, 200, 141, 7, 14, 28, 56, 112, 224, 221, 167, 83, 166, 81, 
    162, 89, 178, 121, 242, 249, 239, 195, 155, 43, 86, 172, 69, 138, 9, 
    18, 36, 72, 144, 61, 122, 244, 245, 247, 243, 251, 235, 203, 139, 11, 
    22, 44, 88, 176, 125, 250, 233, 207, 131, 27, 54, 108, 216, 173, 71, 
    142, 1, 2, 4, 8, 16, 32, 64, 128, 29, 58, 116, 232, 205, 135, 19, 38, 
    76, 152, 45, 90, 180, 117, 234, 201, 143, 3, 6, 12, 24, 48, 96, 192, 
    157, 39, 78, 156, 37, 74, 148, 53, 106, 212, 181, 119, 238, 193, 159, 
    35, 70, 140, 5, 10, 20, 40, 80, 160, 93, 186, 105, 210, 185, 111, 
    222, 161, 95, 190, 97, 194, 153, 47, 94, 188, 101, 202, 137, 15, 30, 
    60, 120, 240, 253, 231, 211, 187, 107, 214, 177, 127, 254, 225, 223, 
    163, 91, 182, 113, 226, 217, 175, 67, 134, 17, 34, 68, 136, 13, 26, 
    52, 104, 208, 189, 103, 206, 129, 31, 62, 124, 248, 237, 199, 147, 
    59, 118, 236, 197, 151, 51, 102, 204, 133, 23, 46, 92, 184, 109, 218, 
    169, 79, 158, 33, 66, 132, 21, 42, 84, 168, 77, 154, 41, 82, 164, 85, 
    170, 73, 146, 57, 114, 228, 213, 183, 115, 230, 209, 191, 99, 198, 
    145, 63, 126, 252, 229, 215, 179, 123, 246, 241, 255, 227, 219, 171, 
    75, 150, 49, 98, 196, 149, 55, 110, 220, 165, 87, 174, 65, 130, 25, 
    50, 100, 200, 141, 7, 14, 28, 56, 112, 224, 221, 167, 83, 166, 81, 
    162, 89, 178, 121, 242, 249, 239, 195, 155, 43, 86, 172, 69, 138, 9, 
    18, 36, 72, 144, 61, 122, 244, 245, 247, 243, 251, 235, 203, 139, 11, 
    22, 44, 88, 176, 125, 250, 233, 207, 131, 27, 54, 108, 216, 173, 71, 
    142 }; 

    double OCT_LOG[255] = { 0, 1, 25, 2, 50, 26, 198, 3, 223, 51, 238, 27, 104, 199, 75, 4, 
    100, 224, 14, 52, 141, 239, 129, 28, 193, 105, 248, 200, 8, 76, 113, 5, 
    138, 101, 47, 225, 36, 15, 33, 53, 147, 142, 218, 240, 18, 130, 69, 
    29, 181, 194, 125, 106, 39, 249, 185, 201, 154, 9, 120, 77, 228, 114, 
    166, 6, 191, 139, 98, 102, 221, 48, 253, 226, 152, 37, 179, 16, 145, 
    34, 136, 54, 208, 148, 206, 143, 150, 219, 189, 241, 210, 19, 92, 
    131, 56, 70, 64, 30, 66, 182, 163, 195, 72, 126, 110, 107, 58, 40, 
    84, 250, 133, 186, 61, 202, 94, 155, 159, 10, 21, 121, 43, 78, 212, 
    229, 172, 115, 243, 167, 87, 7, 112, 192, 247, 140, 128, 99, 13, 103, 
    74, 222, 237, 49, 197, 254, 24, 227, 165, 153, 119, 38, 184, 180, 
    124, 17, 68, 146, 217, 35, 32, 137, 46, 55, 63, 209, 91, 149, 188, 
    207, 205, 144, 135, 151, 178, 220, 252, 190, 97, 242, 86, 211, 171, 
    20, 42, 93, 158, 132, 60, 57, 83, 71, 109, 65, 162, 31, 45, 67, 216, 
    183, 123, 164, 118, 196, 23, 73, 236, 127, 12, 111, 246, 108, 161, 
    59, 82, 41, 157, 85, 170, 251, 96, 134, 177, 187, 204, 62, 90, 203, 
    89, 95, 176, 156, 169, 160, 81, 11, 245, 22, 235, 122, 117, 44, 215, 
    79, 174, 213, 233, 230, 231, 173, 232, 116, 214, 244, 234, 168, 80, 
    88, 175 }; 

    if ((u == 0)||(v == 0)) 
     return 0; 
    else 
    { 
     int index=OCT_LOG[int(u-1)] + OCT_LOG[int(v-1)] + 1; 
     return OCT_EXP [index-1]; 
    } 

} 


void mexFunction(int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[]) 
{ 
    double *u, *v, *uv; 
    int mrows, ncols; 
    plhs[0] = mxCreateDoubleMatrix(1,1, mxREAL); 
    /* Assign pointers to each input and output. */ 
    u = mxGetPr(prhs[0]);  
    v = mxGetPr(prhs[1]); 
    uv = mxGetPr(plhs[0]); 
    *uv = look_up(*u, *v); 
} 

Код измерения

function main 
    function test1() 
     for i=1:200 
      for j=1:200 
       gfmult_no_vec(i,j); 
      end 
     end 
    end 

    function test2() 
     for i=1:200 
      for j=1:200 
       gfmult_vec(i,j); 
      end 
     end 
    end 

    function test3() 
     for i=1:200 
      for j=1:200 
       gfmult_mex(i,j); 
      end 
     end 
    end 
f1=@()test1(); 
t1=timeit(f1) 

f2=@()test2(); 
t2=timeit(f2) 

f3=@()test3(); 
t3=timeit(f3) 
end 

Время Отчет: t1 = 0,1934, t2 = 1,1739, t3 = 0,3584

Answer 1

Это решение принимает 0,0006 второе место в моем компьютере (и он векторизован):

u = randi(5,200,1)-1; % some arbitrary data including zeros 
v = randi(5,200,1)-1; % some arbitrary data including zeros 
[U,V] = ndgrid(u(u~=0),v(v~=0)); % make all possible combinations of u and v 
val = zeros(length(u),length(v)); % initialize the output size, in case the last value in u or v is zero. 
f = @(u,v) OCT_EXP(OCT_LOG(u)+OCT_LOG(v)+1); 
val((u~=0),(v~=0)) = f(U,V); 

Теперь val(u,v) = OCT_EXP(OCT_LOG(u)+OCT_LOG(v)+1), если u и v оба не являются нулями, в противном случае val(u,v) = 0.

---

Если вы хотите gfmult иметь скалярную вход, то ваш первый метод представляется самым быстрым способом. Тем не менее, я бы определил OCT_EXP и OCT_LOG вне функции и передать их к нему, вместо того, чтобы назначить эти значения снова и снова:

function val = gfmult(OCT_EXP,OCT_LOG,u,v) 
if (u==0)||(v==0) 
    val = 0; 
else 
    val = OCT_EXP(OCT_LOG(u)+OCT_LOG(v)+1); 
end 
end 

в моем компьютере это уменьшает время работы от 0.21444 (с вашей версии) в 0.158 секунд для 100K итераций, что не является таким большим улучшением (0.05644 секунды), но если у вас есть миллионы, это может быть значительным.