TopK

Outputs maximum K values of a source vector and their indexes. If same values exist in the source vector, the indexes of theses values calculated by the non-HMPP_TOPK_RADIX algorithm are not sorted. That is, the non-HMPP_TOPK_RADIX algorithm is unstable, and the index sequence after the TopK calculation may be different from that before.

The function calling process is as follows:

Initialize the buffer by calling Init.
Call the main function.
Release the buffer by calling Release.

The function interface declaration is as follows:

Initialization:
HmppResult HMPPS_TopKInit_32s(int32_t srcLen, int32_t *dstValue, int32_t *dstIndex, int32_t dstLen, HmppTopKMode hint, uint8_t **buffer);

HmppResult HMPPS_TopKInit_32f(int32_t srcLen, float *dstValue, int32_t *dstIndex, int32_t dstLen, HmppTopKMode hint, uint8_t **buffer);
Main functions:
HmppResult HMPPS_TopK_32s(const int32_t *src, int32_t srcIndex, int32_t srcStride, int32_t srcLen, int32_t *dstValue, int32_t *dstIndex, int32_t dstLen, HmppTopKMode hint, uint8_t *buffer);

HmppResult HMPPS_TopK_32f(const float *src, int32_t srcIndex, int32_t srcStride, int32_t srcLen, float *dstValue, int32_t *dstIndex, int32_t dstLen, HmppTopKMode hint, uint8_t *buffer);
Memory release:
HmppResult HMPPS_TopKRelease(uint8_t *buffer);

Parameters

Parameter	Description	Value Range	Input/Output
src	Pointer to the source vector	The value cannot be NULL.	Input
srcIndex	Start index (index of pSrc[0])	[0, INT_MAX - srcLen)	Input
srcStride	Stride between elements in the source vector	(0, INT_MAX]	Input
srcLen	Number of elements in the source vector	(0, INT_MAX]	Input
dstValue	Pointer to the maximum K values in the destination vector	The value cannot be NULL.	Output
dstIndex	Pointer to the indexes of maximum K values in the destination vector	The value cannot be NULL.	Output
dstLen	Number of elements in the destination vector	(0, INT_MAX]	Input
hint	Algorithm model used for the calculation	HMPP_TOPK_AUTO, HMPP_TOPK_DIRECT, or HMPP_TOPK_RADIX	Input
buffer (in the Init function)	Pointer to the pointer of the buffer required for calculation	The value cannot be NULL.	Output
buffer (in the main and release functions)	Pointer to the buffer required for calculation	The value cannot be NULL.	Input

Return Value

Success: HMPP_STS_NO_ERR
Failure: An error code is returned.

Error Codes

Error Code	Description
HMPP_STS_NO_ERR	No error occurs.
HMPP_STS_NULL_PTR_ERR	Any of the specified pointers is NULL.
HMPP_STS_SIZE_ERR	The value of srcLen or dstLen is less than or equal to 0.
HMPP_STS_BAD_ARG_ERR	The value of hint is not supported.
HMPP_STS_OVERFLOW	The function overflows.
HMPP_STS_MALLOC_FAILED	The Init function failed to allocate the memory required by the algorithm model.

Note

Before calling this interface, you must call the Init interface to initialize the buffer memory, maximum K values, and indexes of maximum K values.

Example

#define SRC_LEN_S 7
void TopKExample(void){
    int32_t srcLen = SRC_LEN_S;
    int32_t srcIndex = 0;
    int32_t srcStride = 4;
    int32_t dstLen = SRC_LEN_S;
    HmppTopKMode hint = HMPP_TOPK_AUTO;
    int32_t src[SRC_LEN_S] = { 7, 1, 11, 0, 2, 5, 16 };
    int32_t dstValue[SRC_LEN_S] = { 0 };
    int32_t dstIndex[SRC_LEN_S] = { 0 };
    uint8_t *buffer = NULL;
    HmppResult result;
    result = HMPPS_TopKInit_32s(srcLen, dstValue, dstIndex, dstLen, hint, &buffer);
    printf("HMPPS_TopKInit_32s result = %d\n", result);
    if (result != HMPP_STS_NO_ERR) {
        return;
    }
    result = HMPPS_TopK_32s(src, srcIndex, srcStride, srcLen, dstValue, dstIndex, dstLen, hint, buffer);
    printf("HMPPS_TopK_32s result = %d\n", result);
    HMPPS_TopKRelease(buffer);
    if (result != HMPP_STS_NO_ERR) {
        return;
    }
    int32_t i;
    printf("dstLen = %d\ndstValue =", dstLen);
    for(i = 0; i < dstLen; ++i) {
        printf(" %d", dstValue[i]);
    }
    printf("\ndstIndex =");
    for(i = 0; i < dstLen; ++i){
        printf(" %d", dstIndex[i]);
    }
    printf("\n");
}

Output:

HMPPS_TopKInit_32s result = 0
HMPPS_TopK_32s result = 0
dstLen = 7
dstValue = 16 11 7 5 2 1 0
dstIndex = 6 2 0 5 4 1 3

Parent topic: Basic and Common Calculations