diff --git a/lab3/README.md b/lab3/README.md
index d0646ee60e261eea40ca494faafd1f1b0b0baf69..a5ad652d1e0e7ab4c35a2555c50739f80020da12 100644
--- a/lab3/README.md
+++ b/lab3/README.md
@@ -13,6 +13,7 @@ Three hours
# Source Codes
- MPI I/O. Serial hello world in C and Fortran ([hello_mpi.c](hello_mpi.c) and [hello_mpi.f90](hello_mpi.f90))
+- MPI Derived types and I/O. Serial STL file reader in C and Fortran ([mpi_derived_types.c](mpi_derived_types.c) and [mpi_derived_types.f90](mpi_derived_types.f90)
- MPI Latency: C and Fortran ([mpi_latency.c](mpi_latency.c) and [mpi_latency.f90](mpi_latency.f90))
- MPI Bandwidth : C and Fortran ([mpi_bandwidth.c](mpi_bandwidth.c) and [mpi_bandwidth.f90](mpi_bandwidth.f90))
- MPI Bandwidth Non-Blocking: C and Fortran ([mpi_bandwidth-nonblock.c](mpi_bandwidth-nonblock.c)
@@ -29,7 +30,19 @@ MPI I/O is used so that results can be written to the same file in parallel. Tak
The simplest solution is likely to be for you to create a character buffer, and then use the MPI_File_write_at function.
-# Exercises 2 - Bandwidth and latency between nodes
+# Exercise 2 - MPI I/O and dervied types
+
+Take the serial stl reader and modify it such that the stl file is read (and written) in parallel using collective MPI I/O. Use derived types such that the file can be read/written with a maximum of 3 I/O operations per read and write.
+
+The simplest solution is likely to create a derived type for each triangle, and then use the MPI_File_XXXX_at_all function. A correct solution will have the same MD5 hash for both stl models (input and output), unless the order of the triangles has been changed.
+
+```
+md5sum out.stl data/sphere.stl
+822aba6dc20cc0421f92ad50df95464c out.stl
+822aba6dc20cc0421f92ad50df95464c data/sphere.stl
+```
+
+# Exercises 3 - Bandwidth and latency between nodes
Use `mpi_wtime` to compute latency and bandwidth with the bandwidth and latency codes above
diff --git a/lab3/data/sphere.stl b/lab3/data/sphere.stl
new file mode 100644
index 0000000000000000000000000000000000000000..86a17cb221228e88ce977506ae1faeee4077687b
Binary files /dev/null and b/lab3/data/sphere.stl differ
diff --git a/lab3/mpi_derived_types.c b/lab3/mpi_derived_types.c
new file mode 100644
index 0000000000000000000000000000000000000000..45e2153266a7fb15738610abf66bbc18e74dfabd
--- /dev/null
+++ b/lab3/mpi_derived_types.c
@@ -0,0 +1,112 @@
+/*
+ STL file format
+
+ UINT8[80] – Header
+ UINT32 – Number of triangles
+
+ foreach triangle
+ REAL32[3] – Normal vector
+ REAL32[3] – Vertex 1
+ REAL32[3] – Vertex 2
+ REAL32[3] – Vertex 3
+ UINT16 – Attribute byte count
+ end
+
+ (see https://en.wikipedia.org/wiki/STL_(file_format)
+
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+#include <mpi.h>
+
+#define STL_HDR_SIZE 80
+
+typedef struct {
+ float n[3]; /* Normal vector */
+ float v1[3]; /* Vertex 1 */
+ float v2[3]; /* Vertex 2 */
+ float v3[3]; /* Vertex 3 */
+ uint16_t attrib; /* Attribute byte count */
+} __attribute__((packed)) stl_triangle_t;
+
+typedef struct {
+ char hdr[STL_HDR_SIZE]; /* Header */
+ uint32_t n_tri; /* Number of triangles */
+ stl_triangle_t *tri; /* Triangles */
+} stl_model_t;
+
+
+void stl_read(const char *fname, stl_model_t *model) {
+ FILE *fp;
+ int pe_size, pe_rank;
+
+ MPI_Comm_size(MPI_COMM_WORLD, &pe_size);
+ MPI_Comm_rank(MPI_COMM_WORLD, &pe_rank);
+
+ fp = fopen(fname, "r");
+
+ if (pe_rank == 0) printf("Reading STL file: %s\n", fname);
+
+ /* Read STL header */
+ fread(model->hdr, sizeof(char), STL_HDR_SIZE, fp);
+
+ /* Make sure it's a binary STL file */
+ if (strncmp(model->hdr, "solid", 5) == 0) {
+ fprintf(stderr, "ASCII STL files not supported!\n");
+ exit(-1);
+ }
+
+ /* Read how many triangles the file contains */
+ fread(&model->n_tri, sizeof(uint32_t), 1, fp);
+ if (pe_rank == 0) printf("Found: %d triangles\n", model->n_tri);
+
+ /* Allocate memory for triangles, and read them */
+ model->tri = malloc(model->n_tri * sizeof(stl_triangle_t));
+ fread(model->tri, sizeof(stl_triangle_t), model->n_tri, fp);
+
+ fclose(fp);
+ if (pe_rank == 0) printf("Done\n");
+
+}
+
+void stl_write(const char *fname, stl_model_t *model) {
+ FILE *fp;
+ int pe_size, pe_rank;
+
+ MPI_Comm_size(MPI_COMM_WORLD, &pe_size);
+ MPI_Comm_rank(MPI_COMM_WORLD, &pe_rank);
+
+ fp = fopen(fname, "w");
+ if (pe_rank == 0) printf("Writing STL file: %s\n", fname);
+
+ /* Write STL header */
+ fwrite(model->hdr, sizeof(char), STL_HDR_SIZE, fp);
+
+ /* Write number of triangles */
+ fwrite(&model->n_tri, sizeof(uint32_t), 1, fp);
+
+ /* Write all triangles */
+ fwrite(model->tri, sizeof(stl_triangle_t), model->n_tri, fp);
+
+ fclose(fp);
+ if (pe_rank == 0) printf("Done\n");
+}
+
+int main(int argc, char **argv) {
+ stl_model_t model;
+
+ MPI_Init(&argc, &argv);
+
+ stl_read("./data/sphere.stl", &model);
+ stl_write("out.stl", &model);
+ free(model.tri);
+
+ MPI_Finalize();
+
+ return 0;
+}
+
+
diff --git a/lab3/mpi_derived_types.f90 b/lab3/mpi_derived_types.f90
new file mode 100644
index 0000000000000000000000000000000000000000..03b248048c3a2170302669ba47beb5f3cb78cac9
--- /dev/null
+++ b/lab3/mpi_derived_types.f90
@@ -0,0 +1,117 @@
+!
+! STL file format
+!
+! UINT8[80] – Header
+! UINT32 – Number of triangles
+!
+! foreach triangle
+! REAL32[3] – Normal vector
+! REAL32[3] – Vertex 1
+! REAL32[3] – Vertex 2
+! REAL32[3] – Vertex 3
+! UINT16 – Attribute byte count
+! end
+!
+! (see https://en.wikipedia.org/wiki/STL_(file_format)
+!
+module types
+ integer, parameter :: dp = kind(0.0d0)
+ integer, parameter :: sp = kind(0.0)
+end module types
+
+module stl
+ use mpi
+ use types
+ implicit none
+
+ type :: stl_triangle_t
+ real(kind=sp) :: n(3)
+ real(kind=sp) :: v1(3)
+ real(kind=sp) :: v2(3)
+ real(kind=sp) :: v3(3)
+ integer(kind=2) :: attrib
+ end type stl_triangle_t
+
+ type :: stl_model_t
+ character(len=80) :: hdr
+ integer :: n_tri
+ type(stl_triangle_t), allocatable :: tri(:)
+ end type stl_model_t
+
+contains
+
+ subroutine stl_read(fname, model)
+ character(len=*), intent(in) :: fname
+ type(stl_model_t), intent(inout) :: model
+ integer :: pe_size, pe_rank, ierr
+
+ call MPI_Comm_size(MPI_COMM_WORLD, pe_size, ierr)
+ call MPI_Comm_rank(MPI_COMM_WORLD, pe_rank, ierr)
+
+ open(42, file=fname, access='stream', form='unformatted')
+
+ if (pe_rank .eq. 0) write(*,*) 'Reading STL file: ', fname
+ ! Read STL header
+ read(42, pos=1) model%hdr
+
+ ! Make sure it's a binary STL file
+ if (model%hdr(1:6) .eq. 'solid') then
+ write(*,*) 'ASCII STL files not supported!'
+ stop
+ end if
+
+ ! Read how many triangles the file contains
+ read(42, pos=81) model%n_tri
+ if (pe_rank .eq. 0) write(*,*) 'Found: ', model%n_tri,' triangles'
+
+ ! Allocate memory for triangles, and read them
+ allocate(model%tri(model%n_tri))
+ read(42, pos=85) model%tri
+
+ close(42)
+ if (pe_rank .eq. 0) write(*,*) 'Done'
+
+ end subroutine stl_read
+
+ subroutine stl_write(fname, model)
+ character(len=*), intent(in) :: fname
+ type(stl_model_t), intent(in) :: model
+ integer :: pe_size, pe_rank, ierr
+
+ call MPI_Comm_size(MPI_COMM_WORLD, pe_size, ierr)
+ call MPI_Comm_rank(MPI_COMM_WORLD, pe_rank, ierr)
+
+ open(17, file=fname, access='stream', form='unformatted')
+
+ if (pe_rank .eq. 0) write(*,*) 'Writing STL file: ', fname
+
+ ! Write STL header
+ write(17, pos=1) model%hdr
+
+ ! Write number of triangles
+ write(17, pos=81) model%n_tri
+
+ ! Write all triangles
+ write(17, pos=85) model%tri
+
+ close(17)
+ if (pe_rank .eq. 0) write(*,*) 'Done'
+
+ end subroutine stl_write
+end module stl
+
+program mpi_derived_types
+ use stl
+ use mpi
+ implicit none
+ type(stl_model_t) :: model
+ integer :: ierr
+ call MPI_Init(ierr)
+
+ call stl_read("./data/sphere.stl", model)
+ call stl_write("out.stl", model)
+ deallocate(model%tri)
+
+ call MPI_Finalize(ierr)
+
+end program mpi_derived_types