1.  INTRODUCTION

This is a performance report for IA-32 commodity platforms when applied to the Air Quality Model (AQM) AERMOD. New results are presented for AERMOD in two version: the executable model released by the U.S. EPA (hereafter AERMOD-EPA) and the High Performance Computing (HPC) version developed by HiCLAS1 (AERMOD-HPCS). Both version are designed to execute the U.S. EPA's regulatory AERMOD model on a single processor CPU (or core). The purpose of this report is to demonstrate the superior performance of AERMOD-HPCS on commodity architectures. A companion report (HPC-2007-2) continues the Quality Assurance process with a discussion of numerical precision in AERMOD-EPA and AERMOD-HPCS.

2.0 CHOICE OF HARDWARE AND OPERATING SYSTEM

The hardware used for the results reported here is the Intel Pentium 4 Xeon processor with three separate platforms as summarized in Table 1. All platforms used the Microsoft Windows™ operating system for 32-bit architectures. A subsequent report will present results of AERMOD-HPCS on Linux™ operating systems for both 32-bit and 64-bit platforms with a detailed analysis of hardware performance metrics to give insight into why AERMOD-HPCS gives enhanced performance over AERMOD-EPA.

Table 1: Intel Pentium 4 Xeon platforms used in this analysis
Attribute	Machine A	Machine B	Machine C
Clock speed	3.0 GHz	3.06 GHz	3.0 GHz
Front Side Buss speed	800 MHz	533 MHz	800 MHz
L3 cache	none	none	none
L2 cache	1 MB	512 KB	1 MB
L1 cache	16 KB	8 KB	16 KB
	Note: Machines A and C have the same Family and Model of the CPU but have different Stepping and CPU revisions.

3.0 CHOICE OF COMPILERS

The compiler used for AERMOD-EPA executable distributed by the U.S. EPA is not known, but is assumed to the the Compaq Visual Fortran compiler (CVF). The executable distributed by the U.S. EPA was obtained from the distribution center at http://www.epa.gov/scram001 and applied in all the results designated here as AERMOD-EPA. Other results designated here as AERMOD-HPCS were obtained from a compilation of AERMOD-HPCS source code that was modified away from the U.S. EPA source distribution available at the above named U.S. EPA SCRAM Web portal. The compiler used for AERMOD-HPCS in this analysis (and distribution) is un-named but has been chosen after testing of the most popular compilers currently available. Considerable effort has been invested in exhaustively testing multiple compiler options to enable the best performance consistent with the code structure changes implemented at HiCLAS1.

4.0 CHOICE OF BENCHMARKS

The AERMOD model describes pollutant dispersion and deposition and is now an approved regulatory model for new source reviews and other permitting applications. It is available in the AERMOD-EPA version at the U.S. EPA’s Support Center for Regulatory Air Models at the URL portal named above. The version used here is AERMOD 07026 and is designated as AERMOD-EPA. To create the High Performance Computing (HPC) version of AERMOD the source code for the U.S. EPA distribution was progressively modified to enhance performance. The resulting code is designated AERMOD-HPCS, and at v1.7 (the current release) it was deemed to be a sufficient improvement over AERMOD-EPA to warrant exhaustive Quality Assurance (QA) testing. For QA testing the four Cases listed in Table 2 were used as benchmarks. These benchmarks are considered to be representative of actual applications for AERMOD and input and output files for Case 2 are included in the distribution for the purpose of testing the installation after download of the AERMOD-HPCS executable model.

Table 2: Benchmark Cases used in HiCLAS1 Quality Assurance (QA) tests of AERMOD-HPCS
Case	Source type and number				Number of  Receptors	Met Hours
	Point	Area	Volume	Openpit
1	10	0	0	0	916	8760
2	10	5	0	0	916	2160
4	120	0	0	0	771	8760
5	963	38	0	0	916	8760

5.0 BENCHMARK RESULTS

For the machines and cases listed in Tables 1 and 2, respectively, Table 3 shows  the results of this QA performance analysis. The following sections show these results in graphical form.

Table 3: Run times for AERMOD-EPA and AERMOD-HPCS Benchmark Cases used in HiCLAS1 Quality Assurance (QA) tests of AERMOD-HPCS
Case	Machine	AERMOD-EPA runtime (seconds)	AERMOD-HPCS runtime (seconds)	Speedup of AERMOD-HPCS
1	A	868	391	2.22
1	B	540	260	2.08
1	C	651	299	2.18
2	A	1528	798	1.91
2	B	917	483	1.90
2	C	1103	540	2.04
4	A	23583	8264	2.85
4	B	14007	5307	2.64
4	C	16872	6091	2.77
5	A	118879	46495	2.56
5	B	71049	30349	2.34
5	C	TBD	34302	2.54

5.1 Case 1

 Fig. 1: Wall clock time for AERMOD-HPCS compared to that for the U.S. EPA’s distribution for Case 1.

5.2 Case 2

Fig. 2: Wall clock time for AERMOD-HPCS compared to that for the U.S. EPA’s distribution for Case 2.

5.3 Case 4

 

 Fig. 3: Wall clock time for AERMOD-HPCS compared to that for the U.S. EPA’s distribution for Case 4.

5.4 Case 5

 

 Fig. 4: Wall clock time for AERMOD-HPCS compared to that for the U.S. EPA’s distribution for Case 5.

6.0 SPEEDUP OF AERMOD-HPCS OVER AERMOD-EPA

 

Fig.5 displays the ratio of runtimes for AERMOD-HPCS and AERMOD-EPA listed in the last column of Table 3. This shows that, for the Cases listed in Table 2, performance enhancement ranges from 1.9 to 2.77 times faster than AERMOD-EPA (depending on the platform and data set used in the benchmark).

7.0   CONCLUSIONS

This performance analysis of AERMOD-HPCS on Microsoft Windows™ platforms shows that it delivers a solution as much as 2.8 times faster than the U.S. EPA's distribution on the AERMOD executable. Subsequent reports in this series discuss more details of numerical results, the measured hardware performance metrics, and explanations as to why AERMOD-HPCS delivers superior performance when compared to the U.S. EPA distribution.