1,现象
M=N=103040时,调用 sgetrf_ 时,无论是 LAPACK 还是 OpenBLAS,都出错:
openblas:
lapack:
2, 复现代码
出现问题的应该是由于M和N相对数字太大,乘积超出32bit整数的表达范围,而接收此参数的类型其实为 unsigned long int,导致误传非常大的值后造成越界。
如下是已经修复的代码,可以正常运行了:
extern "C" void sgetrf_(int* M, int* N, float* A, int *lda, int* piv, int* info);
#include <stdlib.h>
#include <stdio.h>
#include <cmath>
#include <iostream>
#define ORDER (10304)
//#define ORDER (51520)
void print_matrix(int M, int N, float* A, int lda)
{
for(unsigned long int i=0; i<M; i++){
for(unsigned long int j=0; j<N; j++){
printf(" %7.4f", A[i + j*lda]);
}
printf("\n");
}
}
void init_matrix(int M, int N, float* A, unsigned long int lda, int seed)
{
srand(seed);
for(unsigned long int i=0; i<M; i++){
for(unsigned long int j=0; j<N; j++){
A[i + j*lda] =((float) rand())/RAND_MAX;
}
}
}
int main()
{
float* A = NULL;
int M = ORDER;
int N = M;
int lda = M;
unsigned long int MM = M;
unsigned long int NN = N;
unsigned long int ldaa = lda;
unsigned long int min_MN = std::min(M, N);
int *piv = NULL;
int *info = NULL;
printf("lda * N * sizeof(float) bytes = %ld\n", (ldaa * NN * sizeof(float)));
printf("lda * N * sizeof(float) bytes = %f GB\n", (ldaa * NN * sizeof(float))/1024.0/1024.0/1024.0);
A = (float*)malloc(ldaa * NN * sizeof(float));
if(A==NULL){printf("failed malloc()\n");}
piv = (int*)malloc(min_MN*sizeof(int));
info = (int*)malloc(1*sizeof(int));
init_matrix(M, N, A, lda, 2024);//printf("A =\n"); print_matrix(7, 7, A, lda);
printf("A[%ld] = %7.3f\n", MM -1 + (NN-1)*ldaa, A[MM -1 + (NN-1)*ldaa]);
sgetrf_(&M, &N, A, &lda, piv, info); printf("LU=\n"); print_matrix(7, 7, A, lda);
free(A);
free(piv);
free(info);
return 0;
}
3,结论
遇到非负整数,比如阶数、数组下标等,尽量用 signed long int 类型,代替使用 int 类型,现在的数据量太大了,下标/ 数据量 动辄超过 512M/ 2GB 等;
openblas中的 lapack_int 数据类型:
#define lapack_int int64_t
^
typedef __int64_t int64_t;
^
typedef signed long int __int64_t;
详情如下:
third-party/openblas/local/include/lapack.h
#ifndef lapack_int
#if defined(LAPACK_ILP64)
#define lapack_int int64_t
#else
#define lapack_int int32_t
#endif
#endif
third-party/openblas/OpenBLAS-0.3.27/Makefile.system
LAPACK_CFLAGS += -DLAPACK_ILP64
# 1 "/usr/include/x86_64-linux-gnu/bits/stdint-intn.h" 1 3 4
# 24 "/usr/include/x86_64-linux-gnu/bits/stdint-intn.h" 3 4
typedef __int8_t int8_t;
typedef __int16_t int16_t;
typedef __int32_t int32_t;
typedef __int64_t int64_t;
typedef unsigned char __u_char;
typedef unsigned short int __u_short;
typedef unsigned int __u_int;
typedef unsigned long int __u_long;
typedef signed char __int8_t;
typedef unsigned char __uint8_t;
typedef signed short int __int16_t;
typedef unsigned short int __uint16_t;
typedef signed int __int32_t;
typedef unsigned int __uint32_t;
typedef signed long int __int64_t;
typedef unsigned long int __uint64_t;