#include <stdio.h>

void multiplication(double **matOut, double **matA, int matARows, int matACols, double **matB, int matBRows, int matBCols);

int main(){
   double **matOut, **matA, **matB;
   int matOutRows, matOutCols;
   int matARows, matACols, matBRows, matBCols;
   int i, j;

   matARows = 4;
   matACols = 2;
   matBRows = 2;
   matBCols = 3;

   // メモリ確保
   matOut = malloc(sizeof(double*) * matARows);
   matA = malloc(sizeof(double*) * matARows);
   matB = malloc(sizeof(double*) * matBRows);

   for(i = 0; i < matARows; ++i){
      matOut[i] = malloc(sizeof(double) * matBCols);
      matA[i] = malloc(sizeof(double) * matACols);
   }
   for(i = 0; i < matBRows; ++i){
      matB[i] = malloc(sizeof(double) * matBCols);
   }

   // データ初期化
   for(i = 0; i < matARows; ++i){
      for(j = 0; j < matACols; ++j){
         matA[i][j] = i * matACols + j;
      }
   }

   for(i = 0; i < matBRows; ++i){
      for(j = 0; j < matBCols; ++j){
         matB[i][j] = 3.0;
      }
   }

   for(i = 0; i < matARows; ++i){
      for(j = 0; j < matBCols; ++j){
         matOut[i][j] = 0.0;
      }
   }

   // 初期状態確認
   printf("matrixA initialized\n");
   for(i = 0; i < matARows; ++i){
      for(j = 0; j < matACols; ++j){
         printf("%.3f ", matA[i][j]);
      }
      printf("\n");
   }
   printf("matrixB initialized\n");
   for(i = 0; i < matBRows; ++i){
      for(j = 0; j < matBCols; ++j){
         printf("%.3f ", matB[i][j]);
      }
      printf("\n");
   }

   // 計算
   multiplication(matOut, matA, matARows, matACols, matB, matBRows, matBCols);

   // 計算結果
   printf("matrixOut\n");
   for(i = 0; i < matARows; ++i){
      for(j = 0; j < matBCols; ++j){
         printf("%.3f ", matOut[i][j]);
      }
      printf("\n");
   }

   // メモリ解放
   for(i = 0; i < matARows; ++i){
      free(matOut[i]);
      free(matA[i]);
   }
   for(i = 0; i < matBRows; ++i){
      free(matB[i]);
   }

   free(matOut);
   free(matA);
   free(matB);

   return 0;
}

/*
matOut   : 計算結果
matA     : 入力行列A
matARows : 入力行列Aの行数
matACols : 入力行列Aの列数
matB     : 入力行列B
matBRows : 入力行列Bの行数
matBCols : 入力行列Bの列数
*/
void multiplication(double **matOut, double **matA, int matARows, int matACols, double **matB, int matBRows, int matBCols){
   int i, j, k;
   if( matACols != matBRows ){
      printf("計算できません\n");
      return;
   }

   for(i = 0; i < matARows; ++i){
      for(j = 0; j < matBCols; ++j){
         matOut[i][j] = 0.0;
         for(k = 0; k < matACols; ++k){
            matOut[i][j] += matA[i][k] * matB[k][j];
         }
      }
   }
}