迁移步骤

C语言迁移步骤

第一种：直接迁移

PETSc提供C接口，KML_SCASOLVER同样也提供了C接口，但接口名及接收参数不一致，需要进行对应功能的切换，举例如下：

1. 初始化。
   迁移前：

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   KSP ksp; PetscErrorCode ierr; ierr = KSPCreate(PETSC_COMM_WORLD,&ksp); ierr = KSPSetOperators(ksp,A,A);

   迁移后：

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   int n = 8; int nstripes = 1； int stripeWidth[1]; int stripeRow[1]; int ia[9]; int ja[17]; double a[17]; KmlScasolverTask* handle; int err; err = KmlScaissCgInitStripesDI(&handle, n, nstripes , stripeWidth, stripeRow, a, ja, ia, MPI_COMM_WORLD);

2. 设定求解参数
   迁移前：

   1	ierr = KSPSetTolerances(ksp,1e-4,PETSC_DEFAULT,PETSC_DEFAULT,2000);

   迁移后：

   1 2 3 4

   double eps = 1e-4; err = KmlScaissCgSetDID(&handle, KMLSS_THRESHOLD, &eps, 1); assert(err == 0); int max_iters = 2000; err = KmlScaissCgSetDII(&handle, KMLSS_MAX_ITERATION_COUNT, &max_iters, 1);

3. 求解。
   迁移前：

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   Vec u,x,b; ierr = VecCreate(PETSC_COMM_WORLD,&u); ierr = VecSetSizes(u,PETSC_DECIDE,rdim); ierr = VecSetFromOptions(u);CHKERRQ(ierr); ierr = VecDuplicate(u,&b);CHKERRQ(ierr); ierr = VecDuplicate(b,&x);CHKERRQ(ierr); ierr = KSPSolve(ksp,b,x);CHKERRQ(ierr);

   迁移后：

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   int nb=1; double* x[8]; double* b[8]; int ldx=4; int ldb=4; err = KmlScaissCgSolveDI(&handle, nb, x, ldx, b, ldb);

4. 获取迭代参数。
   迁移前：

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   PetscInt its; PetscScalar norm; ierr = KSPGetIterationNumber(ksp,&its);CHKERRQ(ierr); ierr = KSPGetResidualNorm(ksp,&norm);CHKERRQ(ierr);

   迁移后：

   1 2 3 4

   int idata[] = {max_iters}; err = KmlScaissCgGetDII(&handle, KMLSS_ITERATION_COUNT, data, 1); double ddata[] = {eps}; err = KmlScaissCgGetDID(&handle, KMLSS_TOLERANCE, ddata, 1);

5. 清除。
   迁移前：

   1	ierr = KSPDestroy(&ksp);

   迁移后：

   1	err = KmlScaissCgCleanDI(&handle);

6. 头文件。

   迁移前：

   #include "petscksp.h"

   迁移后：

   #include "kml_scaiss.h"

7. 编译链接。

   替换PETSc相关的链接选项，具体选项请参见《Kunpeng HPCKit 25.1.0 安装指南》安装KML。

第二种：通过适配层迁移

1. 将#include "petscksp.h"改为#include "petscksp_kp.h"，MatCreateMPIAIJWithArrays与VecCreateMPIWithArray接口需要在第二个参数位置新增参数ilower（当前进程上矩阵首行对应的全局下标）。
2. 在编译选项中将原先petsc的头文件路径和动态库路径修改为KML适配层的对应路径，并且重新编译应用，/PATH_TO_KML_INCLUDE为KML头文件路径，/PATH_TO_KML_ADAPTER为KML求解器适配器安装路径，/PATH_TO_KSCASOLVER为kscasolver安装路径，/PATH_TO_KBLAS为kblas安装路径，/PATH_TO_KM 为km安装路径。

   mpicc program.c -I /PATH_TO_KML_INCLUDE -L /PATH_TO_KML_ADAPTER -lpetsc -L /PATH_TO_KSCASOLVER -lkscasolver -lkservice -lklapack_full -L /PATH_TO_KBLAS -lkblas -L /PATH_TO_KM -lkm -lm

   示例：

   mpicc program.c -I ~/HPCKit/latest/kml/gcc/include -L ~/HPCKit/latest/kml/gcc/lib/noarch -lpetsc -L ~/HPCKit/latest/kml/gcc/lib/neon -lkscasolver -lkservice -lklapack_full -L ~/HPCKit/latest/kml/gcc/lib/neon/kblas/multi -lkblas -L ~/HPCKit/latest/kml/gcc/lib/noarch -lkm -lm

3. 添加环境变量。

   export LD_LIBRARY_PATH=/PATH_TO_KML_ADAPTER:/PATH_TO_KSCASOLVER:/PATH_TO_KBLAS:$LD_LIBRARY_PATH

   示例：

   export LD_LIBRARY_PATH=~/HPCKit/latest/kml/gcc/lib/noarch:~/HPCKit/latest/kml/gcc/lib/neon:~/HPCKit/latest/kml/gcc/lib/neon/kblas/multi:$LD_LIBRARY_PATH