---
title: 迁移步骤
description: "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："
url: https://www.hikunpeng.com/document/detail/zh/kunpengboostkithistory/2300/accel/kunpengaccel_12_0060.html
sourcePath: /source/zh/kunpengboostkithistory/2300/accel/kunpengaccel_12_0060.html
indexId: 0e1ba13a3ddf2939a81fc995932f67fd8e161ded89627526cff42bfbd8a424d770
---
# 迁移步骤

#### C语言迁移步骤

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
  ：

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


迁移后
  ：

```
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
  ：

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


迁移后
  ：

```
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
  ：

```
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
  ：

```
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
  ：

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


迁移后
  ：

```
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
  ：

```
ierr = KSPDestroy(&ksp);
```


迁移后
  ：

```
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《鲲鹏数学库 开发指南(https://www.hikunpeng.com/document/detail/zh/kunpengboostkithistory/2300/accel/kunpengaccel_kml_16_0011.html)》中“安装KML”章节的安装后验证内容。